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.
6 Package expect provides support for interpreting structured comments in Go
7 source code as test expectations.
9 This is primarily intended for writing tests of things that process Go source
10 files, although it does not directly depend on the testing package.
12 Collect notes with the Extract or Parse functions, and use the
13 MatchBefore function to find matches within the lines the comments were on.
15 The interpretation of the notes depends on the application.
16 For example, the test suite for a static checking tool might
17 use a @diag note to indicate an expected diagnostic:
19 fmt.Printf("%s", 1) //@ diag("%s wants a string, got int")
21 By contrast, the test suite for a source code navigation tool
22 might use notes to indicate the positions of features of
23 interest, the actions to be performed by the test,
24 and their expected outcomes:
28 print(x) //@ definition("x", x_decl)
29 print(x) //@ typeof("x", "int")
34 Note comments always start with the special marker @, which must be the
35 very first character after the comment opening pair, so //@ or /*@ with no
38 This is followed by a comma separated list of notes.
40 A note always starts with an identifier, which is optionally followed by an
41 argument list. The argument list is surrounded with parentheses and contains a
42 comma-separated list of arguments.
43 The empty parameter list and the missing parameter list are distinguishable if
44 needed; they result in a nil or an empty list in the Args parameter respectively.
46 Arguments are either identifiers or literals.
47 The literals supported are the basic value literals, of string, float, integer
48 true, false or nil. All the literals match the standard go conventions, with
49 all bases of integers, and both quote and backtick strings.
50 There is one extra literal type, which is a string literal preceded by the
51 identifier "re" which is compiled to a regular expression.
62 // Note is a parsed note from an expect comment.
63 // It knows the position of the start of the comment, and the name and
64 // arguments that make up the note.
66 Pos token.Pos // The position at which the note identifier appears
67 Name string // the name associated with the note
68 Args []interface{} // the arguments for the note
71 // ReadFile is the type of a function that can provide file contents for a
73 // This is used in MatchBefore to look up the content of the file in order to
74 // find the line to match the pattern against.
75 type ReadFile func(filename string) ([]byte, error)
77 // MatchBefore attempts to match a pattern in the line before the supplied pos.
78 // It uses the FileSet and the ReadFile to work out the contents of the line
79 // that end is part of, and then matches the pattern against the content of the
80 // start of that line up to the supplied position.
81 // The pattern may be either a simple string, []byte or a *regexp.Regexp.
82 // MatchBefore returns the range of the line that matched the pattern, and
83 // invalid positions if there was no match, or an error if the line could not be
85 func MatchBefore(fset *token.FileSet, readFile ReadFile, end token.Pos, pattern interface{}) (token.Pos, token.Pos, error) {
87 content, err := readFile(f.Name())
89 return token.NoPos, token.NoPos, fmt.Errorf("invalid file: %v", err)
91 position := f.Position(end)
92 startOffset := f.Offset(f.LineStart(position.Line))
93 endOffset := f.Offset(end)
94 line := content[startOffset:endOffset]
95 matchStart, matchEnd := -1, -1
96 switch pattern := pattern.(type) {
98 bytePattern := []byte(pattern)
99 matchStart = bytes.Index(line, bytePattern)
101 matchEnd = matchStart + len(bytePattern)
104 matchStart = bytes.Index(line, pattern)
106 matchEnd = matchStart + len(pattern)
109 match := pattern.FindIndex(line)
111 matchStart = match[0]
116 return token.NoPos, token.NoPos, nil
118 return f.Pos(startOffset + matchStart), f.Pos(startOffset + matchEnd), nil
121 func lineEnd(f *token.File, line int) token.Pos {
122 if line >= f.LineCount() {
123 return token.Pos(f.Base() + f.Size())
125 return f.LineStart(line + 1)