imports.go

     1  // Copyright 2013 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 astutil contains common utilities for working with the Go AST.
     6  package astutil // import "golang.org/x/tools/go/ast/astutil"
     7  
     8  import (
     9  	"fmt"
    10  	"go/ast"
    11  	"go/token"
    12  	"strconv"
    13  	"strings"
    14  )
    15  
    16  // AddImport adds the import path to the file f, if absent.
    17  func AddImport(fset *token.FileSet, f *ast.File, path string) (added bool) {
    18  	return AddNamedImport(fset, f, "", path)
    19  }
    20  
    21  // AddNamedImport adds the import with the given name and path to the file f, if absent.
    22  // If name is not empty, it is used to rename the import.
    23  //
    24  // For example, calling
    25  //
    26  //	AddNamedImport(fset, f, "pathpkg", "path")
    27  //
    28  // adds
    29  //
    30  //	import pathpkg "path"
    31  func AddNamedImport(fset *token.FileSet, f *ast.File, name, path string) (added bool) {
    32  	if imports(f, name, path) {
    33  		return false
    34  	}
    35  
    36  	newImport := &ast.ImportSpec{
    37  		Path: &ast.BasicLit{
    38  			Kind:  token.STRING,
    39  			Value: strconv.Quote(path),
    40  		},
    41  	}
    42  	if name != "" {
    43  		newImport.Name = &ast.Ident{Name: name}
    44  	}
    45  
    46  	// Find an import decl to add to.
    47  	// The goal is to find an existing import
    48  	// whose import path has the longest shared
    49  	// prefix with path.
    50  	var (
    51  		bestMatch  = -1         // length of longest shared prefix
    52  		lastImport = -1         // index in f.Decls of the file's final import decl
    53  		impDecl    *ast.GenDecl // import decl containing the best match
    54  		impIndex   = -1         // spec index in impDecl containing the best match
    55  
    56  		isThirdPartyPath = isThirdParty(path)
    57  	)
    58  	for i, decl := range f.Decls {
    59  		gen, ok := decl.(*ast.GenDecl)
    60  		if ok && gen.Tok == token.IMPORT {
    61  			lastImport = i
    62  			// Do not add to import "C", to avoid disrupting the
    63  			// association with its doc comment, breaking cgo.
    64  			if declImports(gen, "C") {
    65  				continue
    66  			}
    67  
    68  			// Match an empty import decl if that's all that is available.
    69  			if len(gen.Specs) == 0 && bestMatch == -1 {
    70  				impDecl = gen
    71  			}
    72  
    73  			// Compute longest shared prefix with imports in this group and find best
    74  			// matched import spec.
    75  			// 1. Always prefer import spec with longest shared prefix.
    76  			// 2. While match length is 0,
    77  			// - for stdlib package: prefer first import spec.
    78  			// - for third party package: prefer first third party import spec.
    79  			// We cannot use last import spec as best match for third party package
    80  			// because grouped imports are usually placed last by goimports -local
    81  			// flag.
    82  			// See issue #19190.
    83  			seenAnyThirdParty := false
    84  			for j, spec := range gen.Specs {
    85  				impspec := spec.(*ast.ImportSpec)
    86  				p := importPath(impspec)
    87  				n := matchLen(p, path)
    88  				if n > bestMatch || (bestMatch == 0 && !seenAnyThirdParty && isThirdPartyPath) {
    89  					bestMatch = n
    90  					impDecl = gen
    91  					impIndex = j
    92  				}
    93  				seenAnyThirdParty = seenAnyThirdParty || isThirdParty(p)
    94  			}
    95  		}
    96  	}
    97  
    98  	// If no import decl found, add one after the last import.
    99  	if impDecl == nil {
   100  		impDecl = &ast.GenDecl{
   101  			Tok: token.IMPORT,
   102  		}
   103  		if lastImport >= 0 {
   104  			impDecl.TokPos = f.Decls[lastImport].End()
   105  		} else {
   106  			// There are no existing imports.
   107  			// Our new import, preceded by a blank line,  goes after the package declaration
   108  			// and after the comment, if any, that starts on the same line as the
   109  			// package declaration.
   110  			impDecl.TokPos = f.Package
   111  
   112  			file := fset.File(f.Package)
   113  			pkgLine := file.Line(f.Package)
   114  			for _, c := range f.Comments {
   115  				if file.Line(c.Pos()) > pkgLine {
   116  					break
   117  				}
   118  				// +2 for a blank line
   119  				impDecl.TokPos = c.End() + 2
   120  			}
   121  		}
   122  		f.Decls = append(f.Decls, nil)
   123  		copy(f.Decls[lastImport+2:], f.Decls[lastImport+1:])
   124  		f.Decls[lastImport+1] = impDecl
   125  	}
   126  
   127  	// Insert new import at insertAt.
   128  	insertAt := 0
   129  	if impIndex >= 0 {
   130  		// insert after the found import
   131  		insertAt = impIndex + 1
   132  	}
   133  	impDecl.Specs = append(impDecl.Specs, nil)
   134  	copy(impDecl.Specs[insertAt+1:], impDecl.Specs[insertAt:])
   135  	impDecl.Specs[insertAt] = newImport
   136  	pos := impDecl.Pos()
   137  	if insertAt > 0 {
   138  		// If there is a comment after an existing import, preserve the comment
   139  		// position by adding the new import after the comment.
   140  		if spec, ok := impDecl.Specs[insertAt-1].(*ast.ImportSpec); ok && spec.Comment != nil {
   141  			pos = spec.Comment.End()
   142  		} else {
   143  			// Assign same position as the previous import,
   144  			// so that the sorter sees it as being in the same block.
   145  			pos = impDecl.Specs[insertAt-1].Pos()
   146  		}
   147  	}
   148  	if newImport.Name != nil {
   149  		newImport.Name.NamePos = pos
   150  	}
   151  	newImport.Path.ValuePos = pos
   152  	newImport.EndPos = pos
   153  
   154  	// Clean up parens. impDecl contains at least one spec.
   155  	if len(impDecl.Specs) == 1 {
   156  		// Remove unneeded parens.
   157  		impDecl.Lparen = token.NoPos
   158  	} else if !impDecl.Lparen.IsValid() {
   159  		// impDecl needs parens added.
   160  		impDecl.Lparen = impDecl.Specs[0].Pos()
   161  	}
   162  
   163  	f.Imports = append(f.Imports, newImport)
   164  
   165  	if len(f.Decls) <= 1 {
   166  		return true
   167  	}
   168  
   169  	// Merge all the import declarations into the first one.
   170  	var first *ast.GenDecl
   171  	for i := 0; i < len(f.Decls); i++ {
   172  		decl := f.Decls[i]
   173  		gen, ok := decl.(*ast.GenDecl)
   174  		if !ok || gen.Tok != token.IMPORT || declImports(gen, "C") {
   175  			continue
   176  		}
   177  		if first == nil {
   178  			first = gen
   179  			continue // Don't touch the first one.
   180  		}
   181  		// We now know there is more than one package in this import
   182  		// declaration. Ensure that it ends up parenthesized.
   183  		first.Lparen = first.Pos()
   184  		// Move the imports of the other import declaration to the first one.
   185  		for _, spec := range gen.Specs {
   186  			spec.(*ast.ImportSpec).Path.ValuePos = first.Pos()
   187  			first.Specs = append(first.Specs, spec)
   188  		}
   189  		f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
   190  		i--
   191  	}
   192  
   193  	return true
   194  }
   195  
   196  func isThirdParty(importPath string) bool {
   197  	// Third party package import path usually contains "." (".com", ".org", ...)
   198  	// This logic is taken from golang.org/x/tools/imports package.
   199  	return strings.Contains(importPath, ".")
   200  }
   201  
   202  // DeleteImport deletes the import path from the file f, if present.
   203  // If there are duplicate import declarations, all matching ones are deleted.
   204  func DeleteImport(fset *token.FileSet, f *ast.File, path string) (deleted bool) {
   205  	return DeleteNamedImport(fset, f, "", path)
   206  }
   207  
   208  // DeleteNamedImport deletes the import with the given name and path from the file f, if present.
   209  // If there are duplicate import declarations, all matching ones are deleted.
   210  func DeleteNamedImport(fset *token.FileSet, f *ast.File, name, path string) (deleted bool) {
   211  	var delspecs []*ast.ImportSpec
   212  	var delcomments []*ast.CommentGroup
   213  
   214  	// Find the import nodes that import path, if any.
   215  	for i := 0; i < len(f.Decls); i++ {
   216  		decl := f.Decls[i]
   217  		gen, ok := decl.(*ast.GenDecl)
   218  		if !ok || gen.Tok != token.IMPORT {
   219  			continue
   220  		}
   221  		for j := 0; j < len(gen.Specs); j++ {
   222  			spec := gen.Specs[j]
   223  			impspec := spec.(*ast.ImportSpec)
   224  			if importName(impspec) != name || importPath(impspec) != path {
   225  				continue
   226  			}
   227  
   228  			// We found an import spec that imports path.
   229  			// Delete it.
   230  			delspecs = append(delspecs, impspec)
   231  			deleted = true
   232  			copy(gen.Specs[j:], gen.Specs[j+1:])
   233  			gen.Specs = gen.Specs[:len(gen.Specs)-1]
   234  
   235  			// If this was the last import spec in this decl,
   236  			// delete the decl, too.
   237  			if len(gen.Specs) == 0 {
   238  				copy(f.Decls[i:], f.Decls[i+1:])
   239  				f.Decls = f.Decls[:len(f.Decls)-1]
   240  				i--
   241  				break
   242  			} else if len(gen.Specs) == 1 {
   243  				if impspec.Doc != nil {
   244  					delcomments = append(delcomments, impspec.Doc)
   245  				}
   246  				if impspec.Comment != nil {
   247  					delcomments = append(delcomments, impspec.Comment)
   248  				}
   249  				for _, cg := range f.Comments {
   250  					// Found comment on the same line as the import spec.
   251  					if cg.End() < impspec.Pos() && fset.Position(cg.End()).Line == fset.Position(impspec.Pos()).Line {
   252  						delcomments = append(delcomments, cg)
   253  						break
   254  					}
   255  				}
   256  
   257  				spec := gen.Specs[0].(*ast.ImportSpec)
   258  
   259  				// Move the documentation right after the import decl.
   260  				if spec.Doc != nil {
   261  					for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Doc.Pos()).Line {
   262  						fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
   263  					}
   264  				}
   265  				for _, cg := range f.Comments {
   266  					if cg.End() < spec.Pos() && fset.Position(cg.End()).Line == fset.Position(spec.Pos()).Line {
   267  						for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Pos()).Line {
   268  							fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
   269  						}
   270  						break
   271  					}
   272  				}
   273  			}
   274  			if j > 0 {
   275  				lastImpspec := gen.Specs[j-1].(*ast.ImportSpec)
   276  				lastLine := fset.PositionFor(lastImpspec.Path.ValuePos, false).Line
   277  				line := fset.PositionFor(impspec.Path.ValuePos, false).Line
   278  
   279  				// We deleted an entry but now there may be
   280  				// a blank line-sized hole where the import was.
   281  				if line-lastLine > 1 || !gen.Rparen.IsValid() {
   282  					// There was a blank line immediately preceding the deleted import,
   283  					// so there's no need to close the hole. The right parenthesis is
   284  					// invalid after AddImport to an import statement without parenthesis.
   285  					// Do nothing.
   286  				} else if line != fset.File(gen.Rparen).LineCount() {
   287  					// There was no blank line. Close the hole.
   288  					fset.File(gen.Rparen).MergeLine(line)
   289  				}
   290  			}
   291  			j--
   292  		}
   293  	}
   294  
   295  	// Delete imports from f.Imports.
   296  	for i := 0; i < len(f.Imports); i++ {
   297  		imp := f.Imports[i]
   298  		for j, del := range delspecs {
   299  			if imp == del {
   300  				copy(f.Imports[i:], f.Imports[i+1:])
   301  				f.Imports = f.Imports[:len(f.Imports)-1]
   302  				copy(delspecs[j:], delspecs[j+1:])
   303  				delspecs = delspecs[:len(delspecs)-1]
   304  				i--
   305  				break
   306  			}
   307  		}
   308  	}
   309  
   310  	// Delete comments from f.Comments.
   311  	for i := 0; i < len(f.Comments); i++ {
   312  		cg := f.Comments[i]
   313  		for j, del := range delcomments {
   314  			if cg == del {
   315  				copy(f.Comments[i:], f.Comments[i+1:])
   316  				f.Comments = f.Comments[:len(f.Comments)-1]
   317  				copy(delcomments[j:], delcomments[j+1:])
   318  				delcomments = delcomments[:len(delcomments)-1]
   319  				i--
   320  				break
   321  			}
   322  		}
   323  	}
   324  
   325  	if len(delspecs) > 0 {
   326  		panic(fmt.Sprintf("deleted specs from Decls but not Imports: %v", delspecs))
   327  	}
   328  
   329  	return
   330  }
   331  
   332  // RewriteImport rewrites any import of path oldPath to path newPath.
   333  func RewriteImport(fset *token.FileSet, f *ast.File, oldPath, newPath string) (rewrote bool) {
   334  	for _, imp := range f.Imports {
   335  		if importPath(imp) == oldPath {
   336  			rewrote = true
   337  			// record old End, because the default is to compute
   338  			// it using the length of imp.Path.Value.
   339  			imp.EndPos = imp.End()
   340  			imp.Path.Value = strconv.Quote(newPath)
   341  		}
   342  	}
   343  	return
   344  }
   345  
   346  // UsesImport reports whether a given import is used.
   347  func UsesImport(f *ast.File, path string) (used bool) {
   348  	spec := importSpec(f, path)
   349  	if spec == nil {
   350  		return
   351  	}
   352  
   353  	name := spec.Name.String()
   354  	switch name {
   355  	case "<nil>":
   356  		// If the package name is not explicitly specified,
   357  		// make an educated guess. This is not guaranteed to be correct.
   358  		lastSlash := strings.LastIndex(path, "/")
   359  		if lastSlash == -1 {
   360  			name = path
   361  		} else {
   362  			name = path[lastSlash+1:]
   363  		}
   364  	case "_", ".":
   365  		// Not sure if this import is used - err on the side of caution.
   366  		return true
   367  	}
   368  
   369  	ast.Walk(visitFn(func(n ast.Node) {
   370  		sel, ok := n.(*ast.SelectorExpr)
   371  		if ok && isTopName(sel.X, name) {
   372  			used = true
   373  		}
   374  	}), f)
   375  
   376  	return
   377  }
   378  
   379  type visitFn func(node ast.Node)
   380  
   381  func (fn visitFn) Visit(node ast.Node) ast.Visitor {
   382  	fn(node)
   383  	return fn
   384  }
   385  
   386  // imports reports whether f has an import with the specified name and path.
   387  func imports(f *ast.File, name, path string) bool {
   388  	for _, s := range f.Imports {
   389  		if importName(s) == name && importPath(s) == path {
   390  			return true
   391  		}
   392  	}
   393  	return false
   394  }
   395  
   396  // importSpec returns the import spec if f imports path,
   397  // or nil otherwise.
   398  func importSpec(f *ast.File, path string) *ast.ImportSpec {
   399  	for _, s := range f.Imports {
   400  		if importPath(s) == path {
   401  			return s
   402  		}
   403  	}
   404  	return nil
   405  }
   406  
   407  // importName returns the name of s,
   408  // or "" if the import is not named.
   409  func importName(s *ast.ImportSpec) string {
   410  	if s.Name == nil {
   411  		return ""
   412  	}
   413  	return s.Name.Name
   414  }
   415  
   416  // importPath returns the unquoted import path of s,
   417  // or "" if the path is not properly quoted.
   418  func importPath(s *ast.ImportSpec) string {
   419  	t, err := strconv.Unquote(s.Path.Value)
   420  	if err != nil {
   421  		return ""
   422  	}
   423  	return t
   424  }
   425  
   426  // declImports reports whether gen contains an import of path.
   427  func declImports(gen *ast.GenDecl, path string) bool {
   428  	if gen.Tok != token.IMPORT {
   429  		return false
   430  	}
   431  	for _, spec := range gen.Specs {
   432  		impspec := spec.(*ast.ImportSpec)
   433  		if importPath(impspec) == path {
   434  			return true
   435  		}
   436  	}
   437  	return false
   438  }
   439  
   440  // matchLen returns the length of the longest path segment prefix shared by x and y.
   441  func matchLen(x, y string) int {
   442  	n := 0
   443  	for i := 0; i < len(x) && i < len(y) && x[i] == y[i]; i++ {
   444  		if x[i] == '/' {
   445  			n++
   446  		}
   447  	}
   448  	return n
   449  }
   450  
   451  // isTopName returns true if n is a top-level unresolved identifier with the given name.
   452  func isTopName(n ast.Expr, name string) bool {
   453  	id, ok := n.(*ast.Ident)
   454  	return ok && id.Name == name && id.Obj == nil
   455  }
   456  
   457  // Imports returns the file imports grouped by paragraph.
   458  func Imports(fset *token.FileSet, f *ast.File) [][]*ast.ImportSpec {
   459  	var groups [][]*ast.ImportSpec
   460  
   461  	for _, decl := range f.Decls {
   462  		genDecl, ok := decl.(*ast.GenDecl)
   463  		if !ok || genDecl.Tok != token.IMPORT {
   464  			break
   465  		}
   466  
   467  		group := []*ast.ImportSpec{}
   468  
   469  		var lastLine int
   470  		for _, spec := range genDecl.Specs {
   471  			importSpec := spec.(*ast.ImportSpec)
   472  			pos := importSpec.Path.ValuePos
   473  			line := fset.Position(pos).Line
   474  			if lastLine > 0 && pos > 0 && line-lastLine > 1 {
   475  				groups = append(groups, group)
   476  				group = []*ast.ImportSpec{}
   477  			}
   478  			group = append(group, importSpec)
   479  			lastLine = line
   480  		}
   481  		groups = append(groups, group)
   482  	}
   483  
   484  	return groups
   485  }
   486
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