| 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 | // TODO(rsc): Delete this file once Go 1.17 comes out and we can retire Go 1.15 support. |
| 6 | |
| 7 | //go:build !go1.16 |
| 8 | // +build !go1.16 |
| 9 | |
| 10 | // Package buildtag defines an Analyzer that checks build tags. |
| 11 | package buildtag |
| 12 | |
| 13 | import ( |
| 14 | "bytes" |
| 15 | "fmt" |
| 16 | "go/ast" |
| 17 | "go/parser" |
| 18 | "strings" |
| 19 | "unicode" |
| 20 | |
| 21 | "golang.org/x/tools/go/analysis" |
| 22 | "golang.org/x/tools/go/analysis/passes/internal/analysisutil" |
| 23 | ) |
| 24 | |
| 25 | const Doc = "check that +build tags are well-formed and correctly located" |
| 26 | |
| 27 | var Analyzer = &analysis.Analyzer{ |
| 28 | Name: "buildtag", |
| 29 | Doc: Doc, |
| 30 | Run: runBuildTag, |
| 31 | } |
| 32 | |
| 33 | func runBuildTag(pass *analysis.Pass) (interface{}, error) { |
| 34 | for _, f := range pass.Files { |
| 35 | checkGoFile(pass, f) |
| 36 | } |
| 37 | for _, name := range pass.OtherFiles { |
| 38 | if err := checkOtherFile(pass, name); err != nil { |
| 39 | return nil, err |
| 40 | } |
| 41 | } |
| 42 | for _, name := range pass.IgnoredFiles { |
| 43 | if strings.HasSuffix(name, ".go") { |
| 44 | f, err := parser.ParseFile(pass.Fset, name, nil, parser.ParseComments) |
| 45 | if err != nil { |
| 46 | // Not valid Go source code - not our job to diagnose, so ignore. |
| 47 | return nil, nil |
| 48 | } |
| 49 | checkGoFile(pass, f) |
| 50 | } else { |
| 51 | if err := checkOtherFile(pass, name); err != nil { |
| 52 | return nil, err |
| 53 | } |
| 54 | } |
| 55 | } |
| 56 | return nil, nil |
| 57 | } |
| 58 | |
| 59 | func checkGoFile(pass *analysis.Pass, f *ast.File) { |
| 60 | pastCutoff := false |
| 61 | for _, group := range f.Comments { |
| 62 | // A +build comment is ignored after or adjoining the package declaration. |
| 63 | if group.End()+1 >= f.Package { |
| 64 | pastCutoff = true |
| 65 | } |
| 66 | |
| 67 | // "+build" is ignored within or after a /*...*/ comment. |
| 68 | if !strings.HasPrefix(group.List[0].Text, "//") { |
| 69 | pastCutoff = true |
| 70 | continue |
| 71 | } |
| 72 | |
| 73 | // Check each line of a //-comment. |
| 74 | for _, c := range group.List { |
| 75 | if !strings.Contains(c.Text, "+build") { |
| 76 | continue |
| 77 | } |
| 78 | if err := checkLine(c.Text, pastCutoff); err != nil { |
| 79 | pass.Reportf(c.Pos(), "%s", err) |
| 80 | } |
| 81 | } |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | func checkOtherFile(pass *analysis.Pass, filename string) error { |
| 86 | content, tf, err := analysisutil.ReadFile(pass.Fset, filename) |
| 87 | if err != nil { |
| 88 | return err |
| 89 | } |
| 90 | |
| 91 | // We must look at the raw lines, as build tags may appear in non-Go |
| 92 | // files such as assembly files. |
| 93 | lines := bytes.SplitAfter(content, nl) |
| 94 | |
| 95 | // Determine cutpoint where +build comments are no longer valid. |
| 96 | // They are valid in leading // comments in the file followed by |
| 97 | // a blank line. |
| 98 | // |
| 99 | // This must be done as a separate pass because of the |
| 100 | // requirement that the comment be followed by a blank line. |
| 101 | var cutoff int |
| 102 | for i, line := range lines { |
| 103 | line = bytes.TrimSpace(line) |
| 104 | if !bytes.HasPrefix(line, slashSlash) { |
| 105 | if len(line) > 0 { |
| 106 | break |
| 107 | } |
| 108 | cutoff = i |
| 109 | } |
| 110 | } |
| 111 | |
| 112 | for i, line := range lines { |
| 113 | line = bytes.TrimSpace(line) |
| 114 | if !bytes.HasPrefix(line, slashSlash) { |
| 115 | continue |
| 116 | } |
| 117 | if !bytes.Contains(line, []byte("+build")) { |
| 118 | continue |
| 119 | } |
| 120 | if err := checkLine(string(line), i >= cutoff); err != nil { |
| 121 | pass.Reportf(analysisutil.LineStart(tf, i+1), "%s", err) |
| 122 | continue |
| 123 | } |
| 124 | } |
| 125 | return nil |
| 126 | } |
| 127 | |
| 128 | // checkLine checks a line that starts with "//" and contains "+build". |
| 129 | func checkLine(line string, pastCutoff bool) error { |
| 130 | line = strings.TrimPrefix(line, "//") |
| 131 | line = strings.TrimSpace(line) |
| 132 | |
| 133 | if strings.HasPrefix(line, "+build") { |
| 134 | fields := strings.Fields(line) |
| 135 | if fields[0] != "+build" { |
| 136 | // Comment is something like +buildasdf not +build. |
| 137 | return fmt.Errorf("possible malformed +build comment") |
| 138 | } |
| 139 | if pastCutoff { |
| 140 | return fmt.Errorf("+build comment must appear before package clause and be followed by a blank line") |
| 141 | } |
| 142 | if err := checkArguments(fields); err != nil { |
| 143 | return err |
| 144 | } |
| 145 | } else { |
| 146 | // Comment with +build but not at beginning. |
| 147 | if !pastCutoff { |
| 148 | return fmt.Errorf("possible malformed +build comment") |
| 149 | } |
| 150 | } |
| 151 | return nil |
| 152 | } |
| 153 | |
| 154 | func checkArguments(fields []string) error { |
| 155 | for _, arg := range fields[1:] { |
| 156 | for _, elem := range strings.Split(arg, ",") { |
| 157 | if strings.HasPrefix(elem, "!!") { |
| 158 | return fmt.Errorf("invalid double negative in build constraint: %s", arg) |
| 159 | } |
| 160 | elem = strings.TrimPrefix(elem, "!") |
| 161 | for _, c := range elem { |
| 162 | if !unicode.IsLetter(c) && !unicode.IsDigit(c) && c != '_' && c != '.' { |
| 163 | return fmt.Errorf("invalid non-alphanumeric build constraint: %s", arg) |
| 164 | } |
| 165 | } |
| 166 | } |
| 167 | } |
| 168 | return nil |
| 169 | } |
| 170 | |
| 171 | var ( |
| 172 | nl = []byte("\n") |
| 173 | slashSlash = []byte("//") |
| 174 | ) |
| 175 |
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