rule.go

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package modfile implements a parser and formatter for go.mod files.
     6  //
     7  // The go.mod syntax is described in
     8  // https://golang.org/cmd/go/#hdr-The_go_mod_file.
     9  //
    10  // The Parse and ParseLax functions both parse a go.mod file and return an
    11  // abstract syntax tree. ParseLax ignores unknown statements and may be used to
    12  // parse go.mod files that may have been developed with newer versions of Go.
    13  //
    14  // The File struct returned by Parse and ParseLax represent an abstract
    15  // go.mod file. File has several methods like AddNewRequire and DropReplace
    16  // that can be used to programmatically edit a file.
    17  //
    18  // The Format function formats a File back to a byte slice which can be
    19  // written to a file.
    20  package modfile
    21  
    22  import (
    23  	"errors"
    24  	"fmt"
    25  	"path/filepath"
    26  	"sort"
    27  	"strconv"
    28  	"strings"
    29  	"unicode"
    30  
    31  	"golang.org/x/mod/internal/lazyregexp"
    32  	"golang.org/x/mod/module"
    33  	"golang.org/x/mod/semver"
    34  )
    35  
    36  // A File is the parsed, interpreted form of a go.mod file.
    37  type File struct {
    38  	Module  *Module
    39  	Go      *Go
    40  	Require []*Require
    41  	Exclude []*Exclude
    42  	Replace []*Replace
    43  	Retract []*Retract
    44  
    45  	Syntax *FileSyntax
    46  }
    47  
    48  // A Module is the module statement.
    49  type Module struct {
    50  	Mod        module.Version
    51  	Deprecated string
    52  	Syntax     *Line
    53  }
    54  
    55  // A Go is the go statement.
    56  type Go struct {
    57  	Version string // "1.23"
    58  	Syntax  *Line
    59  }
    60  
    61  // An Exclude is a single exclude statement.
    62  type Exclude struct {
    63  	Mod    module.Version
    64  	Syntax *Line
    65  }
    66  
    67  // A Replace is a single replace statement.
    68  type Replace struct {
    69  	Old    module.Version
    70  	New    module.Version
    71  	Syntax *Line
    72  }
    73  
    74  // A Retract is a single retract statement.
    75  type Retract struct {
    76  	VersionInterval
    77  	Rationale string
    78  	Syntax    *Line
    79  }
    80  
    81  // A VersionInterval represents a range of versions with upper and lower bounds.
    82  // Intervals are closed: both bounds are included. When Low is equal to High,
    83  // the interval may refer to a single version ('v1.2.3') or an interval
    84  // ('[v1.2.3, v1.2.3]'); both have the same representation.
    85  type VersionInterval struct {
    86  	Low, High string
    87  }
    88  
    89  // A Require is a single require statement.
    90  type Require struct {
    91  	Mod      module.Version
    92  	Indirect bool // has "// indirect" comment
    93  	Syntax   *Line
    94  }
    95  
    96  func (r *Require) markRemoved() {
    97  	r.Syntax.markRemoved()
    98  	*r = Require{}
    99  }
   100  
   101  func (r *Require) setVersion(v string) {
   102  	r.Mod.Version = v
   103  
   104  	if line := r.Syntax; len(line.Token) > 0 {
   105  		if line.InBlock {
   106  			// If the line is preceded by an empty line, remove it; see
   107  			// https://golang.org/issue/33779.
   108  			if len(line.Comments.Before) == 1 && len(line.Comments.Before[0].Token) == 0 {
   109  				line.Comments.Before = line.Comments.Before[:0]
   110  			}
   111  			if len(line.Token) >= 2 { // example.com v1.2.3
   112  				line.Token[1] = v
   113  			}
   114  		} else {
   115  			if len(line.Token) >= 3 { // require example.com v1.2.3
   116  				line.Token[2] = v
   117  			}
   118  		}
   119  	}
   120  }
   121  
   122  // setIndirect sets line to have (or not have) a "// indirect" comment.
   123  func (r *Require) setIndirect(indirect bool) {
   124  	r.Indirect = indirect
   125  	line := r.Syntax
   126  	if isIndirect(line) == indirect {
   127  		return
   128  	}
   129  	if indirect {
   130  		// Adding comment.
   131  		if len(line.Suffix) == 0 {
   132  			// New comment.
   133  			line.Suffix = []Comment{{Token: "// indirect", Suffix: true}}
   134  			return
   135  		}
   136  
   137  		com := &line.Suffix[0]
   138  		text := strings.TrimSpace(strings.TrimPrefix(com.Token, string(slashSlash)))
   139  		if text == "" {
   140  			// Empty comment.
   141  			com.Token = "// indirect"
   142  			return
   143  		}
   144  
   145  		// Insert at beginning of existing comment.
   146  		com.Token = "// indirect; " + text
   147  		return
   148  	}
   149  
   150  	// Removing comment.
   151  	f := strings.TrimSpace(strings.TrimPrefix(line.Suffix[0].Token, string(slashSlash)))
   152  	if f == "indirect" {
   153  		// Remove whole comment.
   154  		line.Suffix = nil
   155  		return
   156  	}
   157  
   158  	// Remove comment prefix.
   159  	com := &line.Suffix[0]
   160  	i := strings.Index(com.Token, "indirect;")
   161  	com.Token = "//" + com.Token[i+len("indirect;"):]
   162  }
   163  
   164  // isIndirect reports whether line has a "// indirect" comment,
   165  // meaning it is in go.mod only for its effect on indirect dependencies,
   166  // so that it can be dropped entirely once the effective version of the
   167  // indirect dependency reaches the given minimum version.
   168  func isIndirect(line *Line) bool {
   169  	if len(line.Suffix) == 0 {
   170  		return false
   171  	}
   172  	f := strings.Fields(strings.TrimPrefix(line.Suffix[0].Token, string(slashSlash)))
   173  	return (len(f) == 1 && f[0] == "indirect" || len(f) > 1 && f[0] == "indirect;")
   174  }
   175  
   176  func (f *File) AddModuleStmt(path string) error {
   177  	if f.Syntax == nil {
   178  		f.Syntax = new(FileSyntax)
   179  	}
   180  	if f.Module == nil {
   181  		f.Module = &Module{
   182  			Mod:    module.Version{Path: path},
   183  			Syntax: f.Syntax.addLine(nil, "module", AutoQuote(path)),
   184  		}
   185  	} else {
   186  		f.Module.Mod.Path = path
   187  		f.Syntax.updateLine(f.Module.Syntax, "module", AutoQuote(path))
   188  	}
   189  	return nil
   190  }
   191  
   192  func (f *File) AddComment(text string) {
   193  	if f.Syntax == nil {
   194  		f.Syntax = new(FileSyntax)
   195  	}
   196  	f.Syntax.Stmt = append(f.Syntax.Stmt, &CommentBlock{
   197  		Comments: Comments{
   198  			Before: []Comment{
   199  				{
   200  					Token: text,
   201  				},
   202  			},
   203  		},
   204  	})
   205  }
   206  
   207  type VersionFixer func(path, version string) (string, error)
   208  
   209  // errDontFix is returned by a VersionFixer to indicate the version should be
   210  // left alone, even if it's not canonical.
   211  var dontFixRetract VersionFixer = func(_, vers string) (string, error) {
   212  	return vers, nil
   213  }
   214  
   215  // Parse parses and returns a go.mod file.
   216  //
   217  // file is the name of the file, used in positions and errors.
   218  //
   219  // data is the content of the file.
   220  //
   221  // fix is an optional function that canonicalizes module versions.
   222  // If fix is nil, all module versions must be canonical (module.CanonicalVersion
   223  // must return the same string).
   224  func Parse(file string, data []byte, fix VersionFixer) (*File, error) {
   225  	return parseToFile(file, data, fix, true)
   226  }
   227  
   228  // ParseLax is like Parse but ignores unknown statements.
   229  // It is used when parsing go.mod files other than the main module,
   230  // under the theory that most statement types we add in the future will
   231  // only apply in the main module, like exclude and replace,
   232  // and so we get better gradual deployments if old go commands
   233  // simply ignore those statements when found in go.mod files
   234  // in dependencies.
   235  func ParseLax(file string, data []byte, fix VersionFixer) (*File, error) {
   236  	return parseToFile(file, data, fix, false)
   237  }
   238  
   239  func parseToFile(file string, data []byte, fix VersionFixer, strict bool) (parsed *File, err error) {
   240  	fs, err := parse(file, data)
   241  	if err != nil {
   242  		return nil, err
   243  	}
   244  	f := &File{
   245  		Syntax: fs,
   246  	}
   247  	var errs ErrorList
   248  
   249  	// fix versions in retract directives after the file is parsed.
   250  	// We need the module path to fix versions, and it might be at the end.
   251  	defer func() {
   252  		oldLen := len(errs)
   253  		f.fixRetract(fix, &errs)
   254  		if len(errs) > oldLen {
   255  			parsed, err = nil, errs
   256  		}
   257  	}()
   258  
   259  	for _, x := range fs.Stmt {
   260  		switch x := x.(type) {
   261  		case *Line:
   262  			f.add(&errs, nil, x, x.Token[0], x.Token[1:], fix, strict)
   263  
   264  		case *LineBlock:
   265  			if len(x.Token) > 1 {
   266  				if strict {
   267  					errs = append(errs, Error{
   268  						Filename: file,
   269  						Pos:      x.Start,
   270  						Err:      fmt.Errorf("unknown block type: %s", strings.Join(x.Token, " ")),
   271  					})
   272  				}
   273  				continue
   274  			}
   275  			switch x.Token[0] {
   276  			default:
   277  				if strict {
   278  					errs = append(errs, Error{
   279  						Filename: file,
   280  						Pos:      x.Start,
   281  						Err:      fmt.Errorf("unknown block type: %s", strings.Join(x.Token, " ")),
   282  					})
   283  				}
   284  				continue
   285  			case "module", "require", "exclude", "replace", "retract":
   286  				for _, l := range x.Line {
   287  					f.add(&errs, x, l, x.Token[0], l.Token, fix, strict)
   288  				}
   289  			}
   290  		}
   291  	}
   292  
   293  	if len(errs) > 0 {
   294  		return nil, errs
   295  	}
   296  	return f, nil
   297  }
   298  
   299  var GoVersionRE = lazyregexp.New(`^([1-9][0-9]*)\.(0|[1-9][0-9]*)$`)
   300  var laxGoVersionRE = lazyregexp.New(`^v?(([1-9][0-9]*)\.(0|[1-9][0-9]*))([^0-9].*)$`)
   301  
   302  func (f *File) add(errs *ErrorList, block *LineBlock, line *Line, verb string, args []string, fix VersionFixer, strict bool) {
   303  	// If strict is false, this module is a dependency.
   304  	// We ignore all unknown directives as well as main-module-only
   305  	// directives like replace and exclude. It will work better for
   306  	// forward compatibility if we can depend on modules that have unknown
   307  	// statements (presumed relevant only when acting as the main module)
   308  	// and simply ignore those statements.
   309  	if !strict {
   310  		switch verb {
   311  		case "go", "module", "retract", "require":
   312  			// want these even for dependency go.mods
   313  		default:
   314  			return
   315  		}
   316  	}
   317  
   318  	wrapModPathError := func(modPath string, err error) {
   319  		*errs = append(*errs, Error{
   320  			Filename: f.Syntax.Name,
   321  			Pos:      line.Start,
   322  			ModPath:  modPath,
   323  			Verb:     verb,
   324  			Err:      err,
   325  		})
   326  	}
   327  	wrapError := func(err error) {
   328  		*errs = append(*errs, Error{
   329  			Filename: f.Syntax.Name,
   330  			Pos:      line.Start,
   331  			Err:      err,
   332  		})
   333  	}
   334  	errorf := func(format string, args ...interface{}) {
   335  		wrapError(fmt.Errorf(format, args...))
   336  	}
   337  
   338  	switch verb {
   339  	default:
   340  		errorf("unknown directive: %s", verb)
   341  
   342  	case "go":
   343  		if f.Go != nil {
   344  			errorf("repeated go statement")
   345  			return
   346  		}
   347  		if len(args) != 1 {
   348  			errorf("go directive expects exactly one argument")
   349  			return
   350  		} else if !GoVersionRE.MatchString(args[0]) {
   351  			fixed := false
   352  			if !strict {
   353  				if m := laxGoVersionRE.FindStringSubmatch(args[0]); m != nil {
   354  					args[0] = m[1]
   355  					fixed = true
   356  				}
   357  			}
   358  			if !fixed {
   359  				errorf("invalid go version '%s': must match format 1.23", args[0])
   360  				return
   361  			}
   362  		}
   363  
   364  		f.Go = &Go{Syntax: line}
   365  		f.Go.Version = args[0]
   366  
   367  	case "module":
   368  		if f.Module != nil {
   369  			errorf("repeated module statement")
   370  			return
   371  		}
   372  		deprecated := parseDeprecation(block, line)
   373  		f.Module = &Module{
   374  			Syntax:     line,
   375  			Deprecated: deprecated,
   376  		}
   377  		if len(args) != 1 {
   378  			errorf("usage: module module/path")
   379  			return
   380  		}
   381  		s, err := parseString(&args[0])
   382  		if err != nil {
   383  			errorf("invalid quoted string: %v", err)
   384  			return
   385  		}
   386  		f.Module.Mod = module.Version{Path: s}
   387  
   388  	case "require", "exclude":
   389  		if len(args) != 2 {
   390  			errorf("usage: %s module/path v1.2.3", verb)
   391  			return
   392  		}
   393  		s, err := parseString(&args[0])
   394  		if err != nil {
   395  			errorf("invalid quoted string: %v", err)
   396  			return
   397  		}
   398  		v, err := parseVersion(verb, s, &args[1], fix)
   399  		if err != nil {
   400  			wrapError(err)
   401  			return
   402  		}
   403  		pathMajor, err := modulePathMajor(s)
   404  		if err != nil {
   405  			wrapError(err)
   406  			return
   407  		}
   408  		if err := module.CheckPathMajor(v, pathMajor); err != nil {
   409  			wrapModPathError(s, err)
   410  			return
   411  		}
   412  		if verb == "require" {
   413  			f.Require = append(f.Require, &Require{
   414  				Mod:      module.Version{Path: s, Version: v},
   415  				Syntax:   line,
   416  				Indirect: isIndirect(line),
   417  			})
   418  		} else {
   419  			f.Exclude = append(f.Exclude, &Exclude{
   420  				Mod:    module.Version{Path: s, Version: v},
   421  				Syntax: line,
   422  			})
   423  		}
   424  
   425  	case "replace":
   426  		replace, wrappederr := parseReplace(f.Syntax.Name, line, verb, args, fix)
   427  		if wrappederr != nil {
   428  			*errs = append(*errs, *wrappederr)
   429  			return
   430  		}
   431  		f.Replace = append(f.Replace, replace)
   432  
   433  	case "retract":
   434  		rationale := parseDirectiveComment(block, line)
   435  		vi, err := parseVersionInterval(verb, "", &args, dontFixRetract)
   436  		if err != nil {
   437  			if strict {
   438  				wrapError(err)
   439  				return
   440  			} else {
   441  				// Only report errors parsing intervals in the main module. We may
   442  				// support additional syntax in the future, such as open and half-open
   443  				// intervals. Those can't be supported now, because they break the
   444  				// go.mod parser, even in lax mode.
   445  				return
   446  			}
   447  		}
   448  		if len(args) > 0 && strict {
   449  			// In the future, there may be additional information after the version.
   450  			errorf("unexpected token after version: %q", args[0])
   451  			return
   452  		}
   453  		retract := &Retract{
   454  			VersionInterval: vi,
   455  			Rationale:       rationale,
   456  			Syntax:          line,
   457  		}
   458  		f.Retract = append(f.Retract, retract)
   459  	}
   460  }
   461  
   462  func parseReplace(filename string, line *Line, verb string, args []string, fix VersionFixer) (*Replace, *Error) {
   463  	wrapModPathError := func(modPath string, err error) *Error {
   464  		return &Error{
   465  			Filename: filename,
   466  			Pos:      line.Start,
   467  			ModPath:  modPath,
   468  			Verb:     verb,
   469  			Err:      err,
   470  		}
   471  	}
   472  	wrapError := func(err error) *Error {
   473  		return &Error{
   474  			Filename: filename,
   475  			Pos:      line.Start,
   476  			Err:      err,
   477  		}
   478  	}
   479  	errorf := func(format string, args ...interface{}) *Error {
   480  		return wrapError(fmt.Errorf(format, args...))
   481  	}
   482  
   483  	arrow := 2
   484  	if len(args) >= 2 && args[1] == "=>" {
   485  		arrow = 1
   486  	}
   487  	if len(args) < arrow+2 || len(args) > arrow+3 || args[arrow] != "=>" {
   488  		return nil, errorf("usage: %s module/path [v1.2.3] => other/module v1.4\n\t or %s module/path [v1.2.3] => ../local/directory", verb, verb)
   489  	}
   490  	s, err := parseString(&args[0])
   491  	if err != nil {
   492  		return nil, errorf("invalid quoted string: %v", err)
   493  	}
   494  	pathMajor, err := modulePathMajor(s)
   495  	if err != nil {
   496  		return nil, wrapModPathError(s, err)
   497  
   498  	}
   499  	var v string
   500  	if arrow == 2 {
   501  		v, err = parseVersion(verb, s, &args[1], fix)
   502  		if err != nil {
   503  			return nil, wrapError(err)
   504  		}
   505  		if err := module.CheckPathMajor(v, pathMajor); err != nil {
   506  			return nil, wrapModPathError(s, err)
   507  		}
   508  	}
   509  	ns, err := parseString(&args[arrow+1])
   510  	if err != nil {
   511  		return nil, errorf("invalid quoted string: %v", err)
   512  	}
   513  	nv := ""
   514  	if len(args) == arrow+2 {
   515  		if !IsDirectoryPath(ns) {
   516  			return nil, errorf("replacement module without version must be directory path (rooted or starting with ./ or ../)")
   517  		}
   518  		if filepath.Separator == '/' && strings.Contains(ns, `\`) {
   519  			return nil, errorf("replacement directory appears to be Windows path (on a non-windows system)")
   520  		}
   521  	}
   522  	if len(args) == arrow+3 {
   523  		nv, err = parseVersion(verb, ns, &args[arrow+2], fix)
   524  		if err != nil {
   525  			return nil, wrapError(err)
   526  		}
   527  		if IsDirectoryPath(ns) {
   528  			return nil, errorf("replacement module directory path %q cannot have version", ns)
   529  
   530  		}
   531  	}
   532  	return &Replace{
   533  		Old:    module.Version{Path: s, Version: v},
   534  		New:    module.Version{Path: ns, Version: nv},
   535  		Syntax: line,
   536  	}, nil
   537  }
   538  
   539  // fixRetract applies fix to each retract directive in f, appending any errors
   540  // to errs.
   541  //
   542  // Most versions are fixed as we parse the file, but for retract directives,
   543  // the relevant module path is the one specified with the module directive,
   544  // and that might appear at the end of the file (or not at all).
   545  func (f *File) fixRetract(fix VersionFixer, errs *ErrorList) {
   546  	if fix == nil {
   547  		return
   548  	}
   549  	path := ""
   550  	if f.Module != nil {
   551  		path = f.Module.Mod.Path
   552  	}
   553  	var r *Retract
   554  	wrapError := func(err error) {
   555  		*errs = append(*errs, Error{
   556  			Filename: f.Syntax.Name,
   557  			Pos:      r.Syntax.Start,
   558  			Err:      err,
   559  		})
   560  	}
   561  
   562  	for _, r = range f.Retract {
   563  		if path == "" {
   564  			wrapError(errors.New("no module directive found, so retract cannot be used"))
   565  			return // only print the first one of these
   566  		}
   567  
   568  		args := r.Syntax.Token
   569  		if args[0] == "retract" {
   570  			args = args[1:]
   571  		}
   572  		vi, err := parseVersionInterval("retract", path, &args, fix)
   573  		if err != nil {
   574  			wrapError(err)
   575  		}
   576  		r.VersionInterval = vi
   577  	}
   578  }
   579  
   580  func (f *WorkFile) add(errs *ErrorList, line *Line, verb string, args []string, fix VersionFixer) {
   581  	wrapError := func(err error) {
   582  		*errs = append(*errs, Error{
   583  			Filename: f.Syntax.Name,
   584  			Pos:      line.Start,
   585  			Err:      err,
   586  		})
   587  	}
   588  	errorf := func(format string, args ...interface{}) {
   589  		wrapError(fmt.Errorf(format, args...))
   590  	}
   591  
   592  	switch verb {
   593  	default:
   594  		errorf("unknown directive: %s", verb)
   595  
   596  	case "go":
   597  		if f.Go != nil {
   598  			errorf("repeated go statement")
   599  			return
   600  		}
   601  		if len(args) != 1 {
   602  			errorf("go directive expects exactly one argument")
   603  			return
   604  		} else if !GoVersionRE.MatchString(args[0]) {
   605  			errorf("invalid go version '%s': must match format 1.23", args[0])
   606  			return
   607  		}
   608  
   609  		f.Go = &Go{Syntax: line}
   610  		f.Go.Version = args[0]
   611  
   612  	case "use":
   613  		if len(args) != 1 {
   614  			errorf("usage: %s local/dir", verb)
   615  			return
   616  		}
   617  		s, err := parseString(&args[0])
   618  		if err != nil {
   619  			errorf("invalid quoted string: %v", err)
   620  			return
   621  		}
   622  		f.Use = append(f.Use, &Use{
   623  			Path:   s,
   624  			Syntax: line,
   625  		})
   626  
   627  	case "replace":
   628  		replace, wrappederr := parseReplace(f.Syntax.Name, line, verb, args, fix)
   629  		if wrappederr != nil {
   630  			*errs = append(*errs, *wrappederr)
   631  			return
   632  		}
   633  		f.Replace = append(f.Replace, replace)
   634  	}
   635  }
   636  
   637  // IsDirectoryPath reports whether the given path should be interpreted
   638  // as a directory path. Just like on the go command line, relative paths
   639  // and rooted paths are directory paths; the rest are module paths.
   640  func IsDirectoryPath(ns string) bool {
   641  	// Because go.mod files can move from one system to another,
   642  	// we check all known path syntaxes, both Unix and Windows.
   643  	return strings.HasPrefix(ns, "./") || strings.HasPrefix(ns, "../") || strings.HasPrefix(ns, "/") ||
   644  		strings.HasPrefix(ns, `.\`) || strings.HasPrefix(ns, `..\`) || strings.HasPrefix(ns, `\`) ||
   645  		len(ns) >= 2 && ('A' <= ns[0] && ns[0] <= 'Z' || 'a' <= ns[0] && ns[0] <= 'z') && ns[1] == ':'
   646  }
   647  
   648  // MustQuote reports whether s must be quoted in order to appear as
   649  // a single token in a go.mod line.
   650  func MustQuote(s string) bool {
   651  	for _, r := range s {
   652  		switch r {
   653  		case ' ', '"', '\'', '`':
   654  			return true
   655  
   656  		case '(', ')', '[', ']', '{', '}', ',':
   657  			if len(s) > 1 {
   658  				return true
   659  			}
   660  
   661  		default:
   662  			if !unicode.IsPrint(r) {
   663  				return true
   664  			}
   665  		}
   666  	}
   667  	return s == "" || strings.Contains(s, "//") || strings.Contains(s, "/*")
   668  }
   669  
   670  // AutoQuote returns s or, if quoting is required for s to appear in a go.mod,
   671  // the quotation of s.
   672  func AutoQuote(s string) string {
   673  	if MustQuote(s) {
   674  		return strconv.Quote(s)
   675  	}
   676  	return s
   677  }
   678  
   679  func parseVersionInterval(verb string, path string, args *[]string, fix VersionFixer) (VersionInterval, error) {
   680  	toks := *args
   681  	if len(toks) == 0 || toks[0] == "(" {
   682  		return VersionInterval{}, fmt.Errorf("expected '[' or version")
   683  	}
   684  	if toks[0] != "[" {
   685  		v, err := parseVersion(verb, path, &toks[0], fix)
   686  		if err != nil {
   687  			return VersionInterval{}, err
   688  		}
   689  		*args = toks[1:]
   690  		return VersionInterval{Low: v, High: v}, nil
   691  	}
   692  	toks = toks[1:]
   693  
   694  	if len(toks) == 0 {
   695  		return VersionInterval{}, fmt.Errorf("expected version after '['")
   696  	}
   697  	low, err := parseVersion(verb, path, &toks[0], fix)
   698  	if err != nil {
   699  		return VersionInterval{}, err
   700  	}
   701  	toks = toks[1:]
   702  
   703  	if len(toks) == 0 || toks[0] != "," {
   704  		return VersionInterval{}, fmt.Errorf("expected ',' after version")
   705  	}
   706  	toks = toks[1:]
   707  
   708  	if len(toks) == 0 {
   709  		return VersionInterval{}, fmt.Errorf("expected version after ','")
   710  	}
   711  	high, err := parseVersion(verb, path, &toks[0], fix)
   712  	if err != nil {
   713  		return VersionInterval{}, err
   714  	}
   715  	toks = toks[1:]
   716  
   717  	if len(toks) == 0 || toks[0] != "]" {
   718  		return VersionInterval{}, fmt.Errorf("expected ']' after version")
   719  	}
   720  	toks = toks[1:]
   721  
   722  	*args = toks
   723  	return VersionInterval{Low: low, High: high}, nil
   724  }
   725  
   726  func parseString(s *string) (string, error) {
   727  	t := *s
   728  	if strings.HasPrefix(t, `"`) {
   729  		var err error
   730  		if t, err = strconv.Unquote(t); err != nil {
   731  			return "", err
   732  		}
   733  	} else if strings.ContainsAny(t, "\"'`") {
   734  		// Other quotes are reserved both for possible future expansion
   735  		// and to avoid confusion. For example if someone types 'x'
   736  		// we want that to be a syntax error and not a literal x in literal quotation marks.
   737  		return "", fmt.Errorf("unquoted string cannot contain quote")
   738  	}
   739  	*s = AutoQuote(t)
   740  	return t, nil
   741  }
   742  
   743  var deprecatedRE = lazyregexp.New(`(?s)(?:^|\n\n)Deprecated: *(.*?)(?:$|\n\n)`)
   744  
   745  // parseDeprecation extracts the text of comments on a "module" directive and
   746  // extracts a deprecation message from that.
   747  //
   748  // A deprecation message is contained in a paragraph within a block of comments
   749  // that starts with "Deprecated:" (case sensitive). The message runs until the
   750  // end of the paragraph and does not include the "Deprecated:" prefix. If the
   751  // comment block has multiple paragraphs that start with "Deprecated:",
   752  // parseDeprecation returns the message from the first.
   753  func parseDeprecation(block *LineBlock, line *Line) string {
   754  	text := parseDirectiveComment(block, line)
   755  	m := deprecatedRE.FindStringSubmatch(text)
   756  	if m == nil {
   757  		return ""
   758  	}
   759  	return m[1]
   760  }
   761  
   762  // parseDirectiveComment extracts the text of comments on a directive.
   763  // If the directive's line does not have comments and is part of a block that
   764  // does have comments, the block's comments are used.
   765  func parseDirectiveComment(block *LineBlock, line *Line) string {
   766  	comments := line.Comment()
   767  	if block != nil && len(comments.Before) == 0 && len(comments.Suffix) == 0 {
   768  		comments = block.Comment()
   769  	}
   770  	groups := [][]Comment{comments.Before, comments.Suffix}
   771  	var lines []string
   772  	for _, g := range groups {
   773  		for _, c := range g {
   774  			if !strings.HasPrefix(c.Token, "//") {
   775  				continue // blank line
   776  			}
   777  			lines = append(lines, strings.TrimSpace(strings.TrimPrefix(c.Token, "//")))
   778  		}
   779  	}
   780  	return strings.Join(lines, "\n")
   781  }
   782  
   783  type ErrorList []Error
   784  
   785  func (e ErrorList) Error() string {
   786  	errStrs := make([]string, len(e))
   787  	for i, err := range e {
   788  		errStrs[i] = err.Error()
   789  	}
   790  	return strings.Join(errStrs, "\n")
   791  }
   792  
   793  type Error struct {
   794  	Filename string
   795  	Pos      Position
   796  	Verb     string
   797  	ModPath  string
   798  	Err      error
   799  }
   800  
   801  func (e *Error) Error() string {
   802  	var pos string
   803  	if e.Pos.LineRune > 1 {
   804  		// Don't print LineRune if it's 1 (beginning of line).
   805  		// It's always 1 except in scanner errors, which are rare.
   806  		pos = fmt.Sprintf("%s:%d:%d: ", e.Filename, e.Pos.Line, e.Pos.LineRune)
   807  	} else if e.Pos.Line > 0 {
   808  		pos = fmt.Sprintf("%s:%d: ", e.Filename, e.Pos.Line)
   809  	} else if e.Filename != "" {
   810  		pos = fmt.Sprintf("%s: ", e.Filename)
   811  	}
   812  
   813  	var directive string
   814  	if e.ModPath != "" {
   815  		directive = fmt.Sprintf("%s %s: ", e.Verb, e.ModPath)
   816  	} else if e.Verb != "" {
   817  		directive = fmt.Sprintf("%s: ", e.Verb)
   818  	}
   819  
   820  	return pos + directive + e.Err.Error()
   821  }
   822  
   823  func (e *Error) Unwrap() error { return e.Err }
   824  
   825  func parseVersion(verb string, path string, s *string, fix VersionFixer) (string, error) {
   826  	t, err := parseString(s)
   827  	if err != nil {
   828  		return "", &Error{
   829  			Verb:    verb,
   830  			ModPath: path,
   831  			Err: &module.InvalidVersionError{
   832  				Version: *s,
   833  				Err:     err,
   834  			},
   835  		}
   836  	}
   837  	if fix != nil {
   838  		fixed, err := fix(path, t)
   839  		if err != nil {
   840  			if err, ok := err.(*module.ModuleError); ok {
   841  				return "", &Error{
   842  					Verb:    verb,
   843  					ModPath: path,
   844  					Err:     err.Err,
   845  				}
   846  			}
   847  			return "", err
   848  		}
   849  		t = fixed
   850  	} else {
   851  		cv := module.CanonicalVersion(t)
   852  		if cv == "" {
   853  			return "", &Error{
   854  				Verb:    verb,
   855  				ModPath: path,
   856  				Err: &module.InvalidVersionError{
   857  					Version: t,
   858  					Err:     errors.New("must be of the form v1.2.3"),
   859  				},
   860  			}
   861  		}
   862  		t = cv
   863  	}
   864  	*s = t
   865  	return *s, nil
   866  }
   867  
   868  func modulePathMajor(path string) (string, error) {
   869  	_, major, ok := module.SplitPathVersion(path)
   870  	if !ok {
   871  		return "", fmt.Errorf("invalid module path")
   872  	}
   873  	return major, nil
   874  }
   875  
   876  func (f *File) Format() ([]byte, error) {
   877  	return Format(f.Syntax), nil
   878  }
   879  
   880  // Cleanup cleans up the file f after any edit operations.
   881  // To avoid quadratic behavior, modifications like DropRequire
   882  // clear the entry but do not remove it from the slice.
   883  // Cleanup cleans out all the cleared entries.
   884  func (f *File) Cleanup() {
   885  	w := 0
   886  	for _, r := range f.Require {
   887  		if r.Mod.Path != "" {
   888  			f.Require[w] = r
   889  			w++
   890  		}
   891  	}
   892  	f.Require = f.Require[:w]
   893  
   894  	w = 0
   895  	for _, x := range f.Exclude {
   896  		if x.Mod.Path != "" {
   897  			f.Exclude[w] = x
   898  			w++
   899  		}
   900  	}
   901  	f.Exclude = f.Exclude[:w]
   902  
   903  	w = 0
   904  	for _, r := range f.Replace {
   905  		if r.Old.Path != "" {
   906  			f.Replace[w] = r
   907  			w++
   908  		}
   909  	}
   910  	f.Replace = f.Replace[:w]
   911  
   912  	w = 0
   913  	for _, r := range f.Retract {
   914  		if r.Low != "" || r.High != "" {
   915  			f.Retract[w] = r
   916  			w++
   917  		}
   918  	}
   919  	f.Retract = f.Retract[:w]
   920  
   921  	f.Syntax.Cleanup()
   922  }
   923  
   924  func (f *File) AddGoStmt(version string) error {
   925  	if !GoVersionRE.MatchString(version) {
   926  		return fmt.Errorf("invalid language version string %q", version)
   927  	}
   928  	if f.Go == nil {
   929  		var hint Expr
   930  		if f.Module != nil && f.Module.Syntax != nil {
   931  			hint = f.Module.Syntax
   932  		}
   933  		f.Go = &Go{
   934  			Version: version,
   935  			Syntax:  f.Syntax.addLine(hint, "go", version),
   936  		}
   937  	} else {
   938  		f.Go.Version = version
   939  		f.Syntax.updateLine(f.Go.Syntax, "go", version)
   940  	}
   941  	return nil
   942  }
   943  
   944  // AddRequire sets the first require line for path to version vers,
   945  // preserving any existing comments for that line and removing all
   946  // other lines for path.
   947  //
   948  // If no line currently exists for path, AddRequire adds a new line
   949  // at the end of the last require block.
   950  func (f *File) AddRequire(path, vers string) error {
   951  	need := true
   952  	for _, r := range f.Require {
   953  		if r.Mod.Path == path {
   954  			if need {
   955  				r.Mod.Version = vers
   956  				f.Syntax.updateLine(r.Syntax, "require", AutoQuote(path), vers)
   957  				need = false
   958  			} else {
   959  				r.Syntax.markRemoved()
   960  				*r = Require{}
   961  			}
   962  		}
   963  	}
   964  
   965  	if need {
   966  		f.AddNewRequire(path, vers, false)
   967  	}
   968  	return nil
   969  }
   970  
   971  // AddNewRequire adds a new require line for path at version vers at the end of
   972  // the last require block, regardless of any existing require lines for path.
   973  func (f *File) AddNewRequire(path, vers string, indirect bool) {
   974  	line := f.Syntax.addLine(nil, "require", AutoQuote(path), vers)
   975  	r := &Require{
   976  		Mod:    module.Version{Path: path, Version: vers},
   977  		Syntax: line,
   978  	}
   979  	r.setIndirect(indirect)
   980  	f.Require = append(f.Require, r)
   981  }
   982  
   983  // SetRequire updates the requirements of f to contain exactly req, preserving
   984  // the existing block structure and line comment contents (except for 'indirect'
   985  // markings) for the first requirement on each named module path.
   986  //
   987  // The Syntax field is ignored for the requirements in req.
   988  //
   989  // Any requirements not already present in the file are added to the block
   990  // containing the last require line.
   991  //
   992  // The requirements in req must specify at most one distinct version for each
   993  // module path.
   994  //
   995  // If any existing requirements may be removed, the caller should call Cleanup
   996  // after all edits are complete.
   997  func (f *File) SetRequire(req []*Require) {
   998  	type elem struct {
   999  		version  string
  1000  		indirect bool
  1001  	}
  1002  	need := make(map[string]elem)
  1003  	for _, r := range req {
  1004  		if prev, dup := need[r.Mod.Path]; dup && prev.version != r.Mod.Version {
  1005  			panic(fmt.Errorf("SetRequire called with conflicting versions for path %s (%s and %s)", r.Mod.Path, prev.version, r.Mod.Version))
  1006  		}
  1007  		need[r.Mod.Path] = elem{r.Mod.Version, r.Indirect}
  1008  	}
  1009  
  1010  	// Update or delete the existing Require entries to preserve
  1011  	// only the first for each module path in req.
  1012  	for _, r := range f.Require {
  1013  		e, ok := need[r.Mod.Path]
  1014  		if ok {
  1015  			r.setVersion(e.version)
  1016  			r.setIndirect(e.indirect)
  1017  		} else {
  1018  			r.markRemoved()
  1019  		}
  1020  		delete(need, r.Mod.Path)
  1021  	}
  1022  
  1023  	// Add new entries in the last block of the file for any paths that weren't
  1024  	// already present.
  1025  	//
  1026  	// This step is nondeterministic, but the final result will be deterministic
  1027  	// because we will sort the block.
  1028  	for path, e := range need {
  1029  		f.AddNewRequire(path, e.version, e.indirect)
  1030  	}
  1031  
  1032  	f.SortBlocks()
  1033  }
  1034  
  1035  // SetRequireSeparateIndirect updates the requirements of f to contain the given
  1036  // requirements. Comment contents (except for 'indirect' markings) are retained
  1037  // from the first existing requirement for each module path. Like SetRequire,
  1038  // SetRequireSeparateIndirect adds requirements for new paths in req,
  1039  // updates the version and "// indirect" comment on existing requirements,
  1040  // and deletes requirements on paths not in req. Existing duplicate requirements
  1041  // are deleted.
  1042  //
  1043  // As its name suggests, SetRequireSeparateIndirect puts direct and indirect
  1044  // requirements into two separate blocks, one containing only direct
  1045  // requirements, and the other containing only indirect requirements.
  1046  // SetRequireSeparateIndirect may move requirements between these two blocks
  1047  // when their indirect markings change. However, SetRequireSeparateIndirect
  1048  // won't move requirements from other blocks, especially blocks with comments.
  1049  //
  1050  // If the file initially has one uncommented block of requirements,
  1051  // SetRequireSeparateIndirect will split it into a direct-only and indirect-only
  1052  // block. This aids in the transition to separate blocks.
  1053  func (f *File) SetRequireSeparateIndirect(req []*Require) {
  1054  	// hasComments returns whether a line or block has comments
  1055  	// other than "indirect".
  1056  	hasComments := func(c Comments) bool {
  1057  		return len(c.Before) > 0 || len(c.After) > 0 || len(c.Suffix) > 1 ||
  1058  			(len(c.Suffix) == 1 &&
  1059  				strings.TrimSpace(strings.TrimPrefix(c.Suffix[0].Token, string(slashSlash))) != "indirect")
  1060  	}
  1061  
  1062  	// moveReq adds r to block. If r was in another block, moveReq deletes
  1063  	// it from that block and transfers its comments.
  1064  	moveReq := func(r *Require, block *LineBlock) {
  1065  		var line *Line
  1066  		if r.Syntax == nil {
  1067  			line = &Line{Token: []string{AutoQuote(r.Mod.Path), r.Mod.Version}}
  1068  			r.Syntax = line
  1069  			if r.Indirect {
  1070  				r.setIndirect(true)
  1071  			}
  1072  		} else {
  1073  			line = new(Line)
  1074  			*line = *r.Syntax
  1075  			if !line.InBlock && len(line.Token) > 0 && line.Token[0] == "require" {
  1076  				line.Token = line.Token[1:]
  1077  			}
  1078  			r.Syntax.Token = nil // Cleanup will delete the old line.
  1079  			r.Syntax = line
  1080  		}
  1081  		line.InBlock = true
  1082  		block.Line = append(block.Line, line)
  1083  	}
  1084  
  1085  	// Examine existing require lines and blocks.
  1086  	var (
  1087  		// We may insert new requirements into the last uncommented
  1088  		// direct-only and indirect-only blocks. We may also move requirements
  1089  		// to the opposite block if their indirect markings change.
  1090  		lastDirectIndex   = -1
  1091  		lastIndirectIndex = -1
  1092  
  1093  		// If there are no direct-only or indirect-only blocks, a new block may
  1094  		// be inserted after the last require line or block.
  1095  		lastRequireIndex = -1
  1096  
  1097  		// If there's only one require line or block, and it's uncommented,
  1098  		// we'll move its requirements to the direct-only or indirect-only blocks.
  1099  		requireLineOrBlockCount = 0
  1100  
  1101  		// Track the block each requirement belongs to (if any) so we can
  1102  		// move them later.
  1103  		lineToBlock = make(map[*Line]*LineBlock)
  1104  	)
  1105  	for i, stmt := range f.Syntax.Stmt {
  1106  		switch stmt := stmt.(type) {
  1107  		case *Line:
  1108  			if len(stmt.Token) == 0 || stmt.Token[0] != "require" {
  1109  				continue
  1110  			}
  1111  			lastRequireIndex = i
  1112  			requireLineOrBlockCount++
  1113  			if !hasComments(stmt.Comments) {
  1114  				if isIndirect(stmt) {
  1115  					lastIndirectIndex = i
  1116  				} else {
  1117  					lastDirectIndex = i
  1118  				}
  1119  			}
  1120  
  1121  		case *LineBlock:
  1122  			if len(stmt.Token) == 0 || stmt.Token[0] != "require" {
  1123  				continue
  1124  			}
  1125  			lastRequireIndex = i
  1126  			requireLineOrBlockCount++
  1127  			allDirect := len(stmt.Line) > 0 && !hasComments(stmt.Comments)
  1128  			allIndirect := len(stmt.Line) > 0 && !hasComments(stmt.Comments)
  1129  			for _, line := range stmt.Line {
  1130  				lineToBlock[line] = stmt
  1131  				if hasComments(line.Comments) {
  1132  					allDirect = false
  1133  					allIndirect = false
  1134  				} else if isIndirect(line) {
  1135  					allDirect = false
  1136  				} else {
  1137  					allIndirect = false
  1138  				}
  1139  			}
  1140  			if allDirect {
  1141  				lastDirectIndex = i
  1142  			}
  1143  			if allIndirect {
  1144  				lastIndirectIndex = i
  1145  			}
  1146  		}
  1147  	}
  1148  
  1149  	oneFlatUncommentedBlock := requireLineOrBlockCount == 1 &&
  1150  		!hasComments(*f.Syntax.Stmt[lastRequireIndex].Comment())
  1151  
  1152  	// Create direct and indirect blocks if needed. Convert lines into blocks
  1153  	// if needed. If we end up with an empty block or a one-line block,
  1154  	// Cleanup will delete it or convert it to a line later.
  1155  	insertBlock := func(i int) *LineBlock {
  1156  		block := &LineBlock{Token: []string{"require"}}
  1157  		f.Syntax.Stmt = append(f.Syntax.Stmt, nil)
  1158  		copy(f.Syntax.Stmt[i+1:], f.Syntax.Stmt[i:])
  1159  		f.Syntax.Stmt[i] = block
  1160  		return block
  1161  	}
  1162  
  1163  	ensureBlock := func(i int) *LineBlock {
  1164  		switch stmt := f.Syntax.Stmt[i].(type) {
  1165  		case *LineBlock:
  1166  			return stmt
  1167  		case *Line:
  1168  			block := &LineBlock{
  1169  				Token: []string{"require"},
  1170  				Line:  []*Line{stmt},
  1171  			}
  1172  			stmt.Token = stmt.Token[1:] // remove "require"
  1173  			stmt.InBlock = true
  1174  			f.Syntax.Stmt[i] = block
  1175  			return block
  1176  		default:
  1177  			panic(fmt.Sprintf("unexpected statement: %v", stmt))
  1178  		}
  1179  	}
  1180  
  1181  	var lastDirectBlock *LineBlock
  1182  	if lastDirectIndex < 0 {
  1183  		if lastIndirectIndex >= 0 {
  1184  			lastDirectIndex = lastIndirectIndex
  1185  			lastIndirectIndex++
  1186  		} else if lastRequireIndex >= 0 {
  1187  			lastDirectIndex = lastRequireIndex + 1
  1188  		} else {
  1189  			lastDirectIndex = len(f.Syntax.Stmt)
  1190  		}
  1191  		lastDirectBlock = insertBlock(lastDirectIndex)
  1192  	} else {
  1193  		lastDirectBlock = ensureBlock(lastDirectIndex)
  1194  	}
  1195  
  1196  	var lastIndirectBlock *LineBlock
  1197  	if lastIndirectIndex < 0 {
  1198  		lastIndirectIndex = lastDirectIndex + 1
  1199  		lastIndirectBlock = insertBlock(lastIndirectIndex)
  1200  	} else {
  1201  		lastIndirectBlock = ensureBlock(lastIndirectIndex)
  1202  	}
  1203  
  1204  	// Delete requirements we don't want anymore.
  1205  	// Update versions and indirect comments on requirements we want to keep.
  1206  	// If a requirement is in last{Direct,Indirect}Block with the wrong
  1207  	// indirect marking after this, or if the requirement is in an single
  1208  	// uncommented mixed block (oneFlatUncommentedBlock), move it to the
  1209  	// correct block.
  1210  	//
  1211  	// Some blocks may be empty after this. Cleanup will remove them.
  1212  	need := make(map[string]*Require)
  1213  	for _, r := range req {
  1214  		need[r.Mod.Path] = r
  1215  	}
  1216  	have := make(map[string]*Require)
  1217  	for _, r := range f.Require {
  1218  		path := r.Mod.Path
  1219  		if need[path] == nil || have[path] != nil {
  1220  			// Requirement not needed, or duplicate requirement. Delete.
  1221  			r.markRemoved()
  1222  			continue
  1223  		}
  1224  		have[r.Mod.Path] = r
  1225  		r.setVersion(need[path].Mod.Version)
  1226  		r.setIndirect(need[path].Indirect)
  1227  		if need[path].Indirect &&
  1228  			(oneFlatUncommentedBlock || lineToBlock[r.Syntax] == lastDirectBlock) {
  1229  			moveReq(r, lastIndirectBlock)
  1230  		} else if !need[path].Indirect &&
  1231  			(oneFlatUncommentedBlock || lineToBlock[r.Syntax] == lastIndirectBlock) {
  1232  			moveReq(r, lastDirectBlock)
  1233  		}
  1234  	}
  1235  
  1236  	// Add new requirements.
  1237  	for path, r := range need {
  1238  		if have[path] == nil {
  1239  			if r.Indirect {
  1240  				moveReq(r, lastIndirectBlock)
  1241  			} else {
  1242  				moveReq(r, lastDirectBlock)
  1243  			}
  1244  			f.Require = append(f.Require, r)
  1245  		}
  1246  	}
  1247  
  1248  	f.SortBlocks()
  1249  }
  1250  
  1251  func (f *File) DropRequire(path string) error {
  1252  	for _, r := range f.Require {
  1253  		if r.Mod.Path == path {
  1254  			r.Syntax.markRemoved()
  1255  			*r = Require{}
  1256  		}
  1257  	}
  1258  	return nil
  1259  }
  1260  
  1261  // AddExclude adds a exclude statement to the mod file. Errors if the provided
  1262  // version is not a canonical version string
  1263  func (f *File) AddExclude(path, vers string) error {
  1264  	if err := checkCanonicalVersion(path, vers); err != nil {
  1265  		return err
  1266  	}
  1267  
  1268  	var hint *Line
  1269  	for _, x := range f.Exclude {
  1270  		if x.Mod.Path == path && x.Mod.Version == vers {
  1271  			return nil
  1272  		}
  1273  		if x.Mod.Path == path {
  1274  			hint = x.Syntax
  1275  		}
  1276  	}
  1277  
  1278  	f.Exclude = append(f.Exclude, &Exclude{Mod: module.Version{Path: path, Version: vers}, Syntax: f.Syntax.addLine(hint, "exclude", AutoQuote(path), vers)})
  1279  	return nil
  1280  }
  1281  
  1282  func (f *File) DropExclude(path, vers string) error {
  1283  	for _, x := range f.Exclude {
  1284  		if x.Mod.Path == path && x.Mod.Version == vers {
  1285  			x.Syntax.markRemoved()
  1286  			*x = Exclude{}
  1287  		}
  1288  	}
  1289  	return nil
  1290  }
  1291  
  1292  func (f *File) AddReplace(oldPath, oldVers, newPath, newVers string) error {
  1293  	return addReplace(f.Syntax, &f.Replace, oldPath, oldVers, newPath, newVers)
  1294  }
  1295  
  1296  func addReplace(syntax *FileSyntax, replace *[]*Replace, oldPath, oldVers, newPath, newVers string) error {
  1297  	need := true
  1298  	old := module.Version{Path: oldPath, Version: oldVers}
  1299  	new := module.Version{Path: newPath, Version: newVers}
  1300  	tokens := []string{"replace", AutoQuote(oldPath)}
  1301  	if oldVers != "" {
  1302  		tokens = append(tokens, oldVers)
  1303  	}
  1304  	tokens = append(tokens, "=>", AutoQuote(newPath))
  1305  	if newVers != "" {
  1306  		tokens = append(tokens, newVers)
  1307  	}
  1308  
  1309  	var hint *Line
  1310  	for _, r := range *replace {
  1311  		if r.Old.Path == oldPath && (oldVers == "" || r.Old.Version == oldVers) {
  1312  			if need {
  1313  				// Found replacement for old; update to use new.
  1314  				r.New = new
  1315  				syntax.updateLine(r.Syntax, tokens...)
  1316  				need = false
  1317  				continue
  1318  			}
  1319  			// Already added; delete other replacements for same.
  1320  			r.Syntax.markRemoved()
  1321  			*r = Replace{}
  1322  		}
  1323  		if r.Old.Path == oldPath {
  1324  			hint = r.Syntax
  1325  		}
  1326  	}
  1327  	if need {
  1328  		*replace = append(*replace, &Replace{Old: old, New: new, Syntax: syntax.addLine(hint, tokens...)})
  1329  	}
  1330  	return nil
  1331  }
  1332  
  1333  func (f *File) DropReplace(oldPath, oldVers string) error {
  1334  	for _, r := range f.Replace {
  1335  		if r.Old.Path == oldPath && r.Old.Version == oldVers {
  1336  			r.Syntax.markRemoved()
  1337  			*r = Replace{}
  1338  		}
  1339  	}
  1340  	return nil
  1341  }
  1342  
  1343  // AddRetract adds a retract statement to the mod file. Errors if the provided
  1344  // version interval does not consist of canonical version strings
  1345  func (f *File) AddRetract(vi VersionInterval, rationale string) error {
  1346  	var path string
  1347  	if f.Module != nil {
  1348  		path = f.Module.Mod.Path
  1349  	}
  1350  	if err := checkCanonicalVersion(path, vi.High); err != nil {
  1351  		return err
  1352  	}
  1353  	if err := checkCanonicalVersion(path, vi.Low); err != nil {
  1354  		return err
  1355  	}
  1356  
  1357  	r := &Retract{
  1358  		VersionInterval: vi,
  1359  	}
  1360  	if vi.Low == vi.High {
  1361  		r.Syntax = f.Syntax.addLine(nil, "retract", AutoQuote(vi.Low))
  1362  	} else {
  1363  		r.Syntax = f.Syntax.addLine(nil, "retract", "[", AutoQuote(vi.Low), ",", AutoQuote(vi.High), "]")
  1364  	}
  1365  	if rationale != "" {
  1366  		for _, line := range strings.Split(rationale, "\n") {
  1367  			com := Comment{Token: "// " + line}
  1368  			r.Syntax.Comment().Before = append(r.Syntax.Comment().Before, com)
  1369  		}
  1370  	}
  1371  	return nil
  1372  }
  1373  
  1374  func (f *File) DropRetract(vi VersionInterval) error {
  1375  	for _, r := range f.Retract {
  1376  		if r.VersionInterval == vi {
  1377  			r.Syntax.markRemoved()
  1378  			*r = Retract{}
  1379  		}
  1380  	}
  1381  	return nil
  1382  }
  1383  
  1384  func (f *File) SortBlocks() {
  1385  	f.removeDups() // otherwise sorting is unsafe
  1386  
  1387  	for _, stmt := range f.Syntax.Stmt {
  1388  		block, ok := stmt.(*LineBlock)
  1389  		if !ok {
  1390  			continue
  1391  		}
  1392  		less := lineLess
  1393  		if block.Token[0] == "retract" {
  1394  			less = lineRetractLess
  1395  		}
  1396  		sort.SliceStable(block.Line, func(i, j int) bool {
  1397  			return less(block.Line[i], block.Line[j])
  1398  		})
  1399  	}
  1400  }
  1401  
  1402  // removeDups removes duplicate exclude and replace directives.
  1403  //
  1404  // Earlier exclude directives take priority.
  1405  //
  1406  // Later replace directives take priority.
  1407  //
  1408  // require directives are not de-duplicated. That's left up to higher-level
  1409  // logic (MVS).
  1410  //
  1411  // retract directives are not de-duplicated since comments are
  1412  // meaningful, and versions may be retracted multiple times.
  1413  func (f *File) removeDups() {
  1414  	removeDups(f.Syntax, &f.Exclude, &f.Replace)
  1415  }
  1416  
  1417  func removeDups(syntax *FileSyntax, exclude *[]*Exclude, replace *[]*Replace) {
  1418  	kill := make(map[*Line]bool)
  1419  
  1420  	// Remove duplicate excludes.
  1421  	if exclude != nil {
  1422  		haveExclude := make(map[module.Version]bool)
  1423  		for _, x := range *exclude {
  1424  			if haveExclude[x.Mod] {
  1425  				kill[x.Syntax] = true
  1426  				continue
  1427  			}
  1428  			haveExclude[x.Mod] = true
  1429  		}
  1430  		var excl []*Exclude
  1431  		for _, x := range *exclude {
  1432  			if !kill[x.Syntax] {
  1433  				excl = append(excl, x)
  1434  			}
  1435  		}
  1436  		*exclude = excl
  1437  	}
  1438  
  1439  	// Remove duplicate replacements.
  1440  	// Later replacements take priority over earlier ones.
  1441  	haveReplace := make(map[module.Version]bool)
  1442  	for i := len(*replace) - 1; i >= 0; i-- {
  1443  		x := (*replace)[i]
  1444  		if haveReplace[x.Old] {
  1445  			kill[x.Syntax] = true
  1446  			continue
  1447  		}
  1448  		haveReplace[x.Old] = true
  1449  	}
  1450  	var repl []*Replace
  1451  	for _, x := range *replace {
  1452  		if !kill[x.Syntax] {
  1453  			repl = append(repl, x)
  1454  		}
  1455  	}
  1456  	*replace = repl
  1457  
  1458  	// Duplicate require and retract directives are not removed.
  1459  
  1460  	// Drop killed statements from the syntax tree.
  1461  	var stmts []Expr
  1462  	for _, stmt := range syntax.Stmt {
  1463  		switch stmt := stmt.(type) {
  1464  		case *Line:
  1465  			if kill[stmt] {
  1466  				continue
  1467  			}
  1468  		case *LineBlock:
  1469  			var lines []*Line
  1470  			for _, line := range stmt.Line {
  1471  				if !kill[line] {
  1472  					lines = append(lines, line)
  1473  				}
  1474  			}
  1475  			stmt.Line = lines
  1476  			if len(lines) == 0 {
  1477  				continue
  1478  			}
  1479  		}
  1480  		stmts = append(stmts, stmt)
  1481  	}
  1482  	syntax.Stmt = stmts
  1483  }
  1484  
  1485  // lineLess returns whether li should be sorted before lj. It sorts
  1486  // lexicographically without assigning any special meaning to tokens.
  1487  func lineLess(li, lj *Line) bool {
  1488  	for k := 0; k < len(li.Token) && k < len(lj.Token); k++ {
  1489  		if li.Token[k] != lj.Token[k] {
  1490  			return li.Token[k] < lj.Token[k]
  1491  		}
  1492  	}
  1493  	return len(li.Token) < len(lj.Token)
  1494  }
  1495  
  1496  // lineRetractLess returns whether li should be sorted before lj for lines in
  1497  // a "retract" block. It treats each line as a version interval. Single versions
  1498  // are compared as if they were intervals with the same low and high version.
  1499  // Intervals are sorted in descending order, first by low version, then by
  1500  // high version, using semver.Compare.
  1501  func lineRetractLess(li, lj *Line) bool {
  1502  	interval := func(l *Line) VersionInterval {
  1503  		if len(l.Token) == 1 {
  1504  			return VersionInterval{Low: l.Token[0], High: l.Token[0]}
  1505  		} else if len(l.Token) == 5 && l.Token[0] == "[" && l.Token[2] == "," && l.Token[4] == "]" {
  1506  			return VersionInterval{Low: l.Token[1], High: l.Token[3]}
  1507  		} else {
  1508  			// Line in unknown format. Treat as an invalid version.
  1509  			return VersionInterval{}
  1510  		}
  1511  	}
  1512  	vii := interval(li)
  1513  	vij := interval(lj)
  1514  	if cmp := semver.Compare(vii.Low, vij.Low); cmp != 0 {
  1515  		return cmp > 0
  1516  	}
  1517  	return semver.Compare(vii.High, vij.High) > 0
  1518  }
  1519  
  1520  // checkCanonicalVersion returns a non-nil error if vers is not a canonical
  1521  // version string or does not match the major version of path.
  1522  //
  1523  // If path is non-empty, the error text suggests a format with a major version
  1524  // corresponding to the path.
  1525  func checkCanonicalVersion(path, vers string) error {
  1526  	_, pathMajor, pathMajorOk := module.SplitPathVersion(path)
  1527  
  1528  	if vers == "" || vers != module.CanonicalVersion(vers) {
  1529  		if pathMajor == "" {
  1530  			return &module.InvalidVersionError{
  1531  				Version: vers,
  1532  				Err:     fmt.Errorf("must be of the form v1.2.3"),
  1533  			}
  1534  		}
  1535  		return &module.InvalidVersionError{
  1536  			Version: vers,
  1537  			Err:     fmt.Errorf("must be of the form %s.2.3", module.PathMajorPrefix(pathMajor)),
  1538  		}
  1539  	}
  1540  
  1541  	if pathMajorOk {
  1542  		if err := module.CheckPathMajor(vers, pathMajor); err != nil {
  1543  			if pathMajor == "" {
  1544  				// In this context, the user probably wrote "v2.3.4" when they meant
  1545  				// "v2.3.4+incompatible". Suggest that instead of "v0 or v1".
  1546  				return &module.InvalidVersionError{
  1547  					Version: vers,
  1548  					Err:     fmt.Errorf("should be %s+incompatible (or module %s/%v)", vers, path, semver.Major(vers)),
  1549  				}
  1550  			}
  1551  			return err
  1552  		}
  1553  	}
  1554  
  1555  	return nil
  1556  }
  1557
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