mirror of
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81 lines
2.5 KiB
Go
81 lines
2.5 KiB
Go
// Package generated provides a function that parses a Go file and reports
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// whether it contains a "// Code generated … DO NOT EDIT." line comment.
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//
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// It implements the specification at https://golang.org/s/generatedcode.
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//
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// The first priority is correctness (no false negatives, no false positives).
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// It must return accurate results even if the input Go source code is not gofmted.
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//
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// The second priority is performance. The current version uses bufio.Reader and
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// ReadBytes. Performance can be optimized further by using lower level I/O
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// primitives and allocating less. That can be explored later. A lot of the time
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// is spent on reading the entire file without being able to stop early,
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// since the specification allows the comment to appear anywhere in the file.
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package generated
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import (
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"bufio"
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"bytes"
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"io"
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"os"
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)
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// Parse parses the source code of a single Go source file
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// provided via src, and reports whether the file contains
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// a "// Code generated ... DO NOT EDIT." line comment
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// matching the specification at https://golang.org/s/generatedcode:
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//
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// Generated files are marked by a line of text that matches
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// the regular expression, in Go syntax:
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//
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// `^// Code generated .* DO NOT EDIT\.$`
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//
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// The .* means the tool can put whatever folderol it wants in there,
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// but the comment must be a single line and must start with `Code generated`
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// and end with `DO NOT EDIT.`, with a period.
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//
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// The text may appear anywhere in the file.
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func Parse(src io.Reader) (hasGeneratedComment bool, err error) {
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br := bufio.NewReader(src)
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for {
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s, err := br.ReadBytes('\n')
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if err == io.EOF {
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return containsComment(s), nil
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} else if err != nil {
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return false, err
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}
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if len(s) >= 2 && s[len(s)-2] == '\r' {
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s = s[:len(s)-2] // Trim "\r\n".
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} else {
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s = s[:len(s)-1] // Trim "\n".
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}
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if containsComment(s) {
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return true, nil
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}
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}
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}
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// containsComment reports whether a line of Go source code s (without newline character)
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// contains the generated comment.
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func containsComment(s []byte) bool {
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return len(s) >= len(prefix)+len(suffix) &&
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bytes.HasPrefix(s, prefix) &&
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bytes.HasSuffix(s, suffix)
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}
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var (
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prefix = []byte("// Code generated ")
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suffix = []byte(" DO NOT EDIT.")
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)
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// ParseFile opens the file specified by filename and uses Parse to parse it.
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// If the source couldn't be read, the error indicates the specific failure.
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func ParseFile(filename string) (hasGeneratedComment bool, err error) {
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f, err := os.Open(filename)
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if err != nil {
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return false, err
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}
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defer f.Close()
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return Parse(f)
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}
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