plusbuild.go

     1  // Copyright 2025 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 modernize
     6  
     7  import (
     8  	"go/ast"
     9  	"go/parser"
    10  	"strings"
    11  
    12  	"golang.org/x/tools/go/analysis"
    13  	"golang.org/x/tools/internal/analysis/analyzerutil"
    14  	"golang.org/x/tools/internal/versions"
    15  )
    16  
    17  var PlusBuildAnalyzer = &analysis.Analyzer{
    18  	Name: "plusbuild",
    19  	Doc:  analyzerutil.MustExtractDoc(doc, "plusbuild"),
    20  	URL:  "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/modernize#plusbuild",
    21  	Run:  plusbuild,
    22  }
    23  
    24  func plusbuild(pass *analysis.Pass) (any, error) {
    25  	check := func(f *ast.File) {
    26  		// "//go:build" directives were added in go1.17, but
    27  		// we didn't start eliminating +build directives till go1.18.
    28  		if !analyzerutil.FileUsesGoVersion(pass, f, versions.Go1_18) {
    29  			return
    30  		}
    31  
    32  		// When gofmt sees a +build comment, it adds a
    33  		// preceding equivalent //go:build directive, so in
    34  		// formatted files we can assume that a +build line is
    35  		// part of a comment group that starts with a
    36  		// //go:build line and is followed by a blank line.
    37  		//
    38  		// While we cannot delete comments from an AST and
    39  		// expect consistent output in general, this specific
    40  		// case--deleting only some lines from a comment
    41  		// block--does format correctly.
    42  		for _, g := range f.Comments {
    43  			sawGoBuild := false
    44  			for _, c := range g.List {
    45  				if sawGoBuild && strings.HasPrefix(c.Text, "// +build ") {
    46  					pass.Report(analysis.Diagnostic{
    47  						Pos:     c.Pos(),
    48  						End:     c.End(),
    49  						Message: "+build line is no longer needed",
    50  						SuggestedFixes: []analysis.SuggestedFix{{
    51  							Message: "Remove obsolete +build line",
    52  							TextEdits: []analysis.TextEdit{{
    53  								Pos: c.Pos(),
    54  								End: c.End(),
    55  							}},
    56  						}},
    57  					})
    58  					break
    59  				}
    60  				if strings.HasPrefix(c.Text, "//go:build ") {
    61  					sawGoBuild = true
    62  				}
    63  			}
    64  		}
    65  	}
    66  
    67  	for _, f := range pass.Files {
    68  		check(f)
    69  	}
    70  	for _, name := range pass.IgnoredFiles {
    71  		if strings.HasSuffix(name, ".go") {
    72  			f, err := parser.ParseFile(pass.Fset, name, nil, parser.ParseComments|parser.SkipObjectResolution)
    73  			if err != nil {
    74  				continue // parse error: ignore
    75  			}
    76  			check(f)
    77  		}
    78  	}
    79  	return nil, nil
    80  }
    81
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