56 lines
1.4 KiB
Go
56 lines
1.4 KiB
Go
package dedent
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import (
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"regexp"
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"strings"
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)
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var whitespaceOnly = regexp.MustCompile("(?m)^[ \t]+$")
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var leadingWhitespace = regexp.MustCompile("(?m)(^[ \t]*)")
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// Dedent removes any common leading whitespace from every line in s.
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//
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// This can be used to make multiline strings to line up with the left edge of
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// the display, while still presenting them in the source code in indented
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// form.
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func Dedent(s string) string {
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s = whitespaceOnly.ReplaceAllString(s, "")
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margin := findMargin(s)
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if len(margin) == 0 {
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return s
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}
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return regexp.MustCompile("(?m)^"+margin).ReplaceAllString(s, "")
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}
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// Look for the longest leading string of spaces and tabs common to all lines.
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func findMargin(s string) string {
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var margin string
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indents := leadingWhitespace.FindAllString(s, -1)
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numIndents := len(indents)
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for i, indent := range indents {
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// Don't use last row if it is empty
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if i == numIndents-1 && indent == "" {
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break
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}
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if margin == "" {
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margin = indent
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} else if strings.HasPrefix(indent, margin) {
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// Current line more deeply indented than previous winner:
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// no change (previous winner is still on top).
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continue
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} else if strings.HasPrefix(margin, indent) {
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// Current line consistent with and no deeper than previous winner:
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// it's the new winner.
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margin = indent
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} else {
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// Current line and previous winner have no common whitespace:
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// there is no margin.
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margin = ""
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break
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}
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}
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return margin
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}
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