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Diffstat (limited to '')
| -rw-r--r-- | src/go/printer/gobuild.go | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/src/go/printer/gobuild.go b/src/go/printer/gobuild.go new file mode 100644 index 0000000..f00492d --- /dev/null +++ b/src/go/printer/gobuild.go @@ -0,0 +1,170 @@ +// Copyright 2020 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package printer + +import ( + "go/build/constraint" + "sort" + "text/tabwriter" +) + +func (p *printer) fixGoBuildLines() { + if len(p.goBuild)+len(p.plusBuild) == 0 { + return + } + + // Find latest possible placement of //go:build and // +build comments. + // That's just after the last blank line before we find a non-comment. + // (We'll add another blank line after our comment block.) + // When we start dropping // +build comments, we can skip over /* */ comments too. + // Note that we are processing tabwriter input, so every comment + // begins and ends with a tabwriter.Escape byte. + // And some newlines have turned into \f bytes. + insert := 0 + for pos := 0; ; { + // Skip leading space at beginning of line. + blank := true + for pos < len(p.output) && (p.output[pos] == ' ' || p.output[pos] == '\t') { + pos++ + } + // Skip over // comment if any. + if pos+3 < len(p.output) && p.output[pos] == tabwriter.Escape && p.output[pos+1] == '/' && p.output[pos+2] == '/' { + blank = false + for pos < len(p.output) && !isNL(p.output[pos]) { + pos++ + } + } + // Skip over \n at end of line. + if pos >= len(p.output) || !isNL(p.output[pos]) { + break + } + pos++ + + if blank { + insert = pos + } + } + + // If there is a //go:build comment before the place we identified, + // use that point instead. (Earlier in the file is always fine.) + if len(p.goBuild) > 0 && p.goBuild[0] < insert { + insert = p.goBuild[0] + } else if len(p.plusBuild) > 0 && p.plusBuild[0] < insert { + insert = p.plusBuild[0] + } + + var x constraint.Expr + switch len(p.goBuild) { + case 0: + // Synthesize //go:build expression from // +build lines. + for _, pos := range p.plusBuild { + y, err := constraint.Parse(p.commentTextAt(pos)) + if err != nil { + x = nil + break + } + if x == nil { + x = y + } else { + x = &constraint.AndExpr{X: x, Y: y} + } + } + case 1: + // Parse //go:build expression. + x, _ = constraint.Parse(p.commentTextAt(p.goBuild[0])) + } + + var block []byte + if x == nil { + // Don't have a valid //go:build expression to treat as truth. + // Bring all the lines together but leave them alone. + // Note that these are already tabwriter-escaped. + for _, pos := range p.goBuild { + block = append(block, p.lineAt(pos)...) + } + for _, pos := range p.plusBuild { + block = append(block, p.lineAt(pos)...) + } + } else { + block = append(block, tabwriter.Escape) + block = append(block, "//go:build "...) + block = append(block, x.String()...) + block = append(block, tabwriter.Escape, '\n') + if len(p.plusBuild) > 0 { + lines, err := constraint.PlusBuildLines(x) + if err != nil { + lines = []string{"// +build error: " + err.Error()} + } + for _, line := range lines { + block = append(block, tabwriter.Escape) + block = append(block, line...) + block = append(block, tabwriter.Escape, '\n') + } + } + } + block = append(block, '\n') + + // Build sorted list of lines to delete from remainder of output. + toDelete := append(p.goBuild, p.plusBuild...) + sort.Ints(toDelete) + + // Collect output after insertion point, with lines deleted, into after. + var after []byte + start := insert + for _, end := range toDelete { + if end < start { + continue + } + after = appendLines(after, p.output[start:end]) + start = end + len(p.lineAt(end)) + } + after = appendLines(after, p.output[start:]) + if n := len(after); n >= 2 && isNL(after[n-1]) && isNL(after[n-2]) { + after = after[:n-1] + } + + p.output = p.output[:insert] + p.output = append(p.output, block...) + p.output = append(p.output, after...) +} + +// appendLines is like append(x, y...) +// but it avoids creating doubled blank lines, +// which would not be gofmt-standard output. +// It assumes that only whole blocks of lines are being appended, +// not line fragments. +func appendLines(x, y []byte) []byte { + if len(y) > 0 && isNL(y[0]) && // y starts in blank line + (len(x) == 0 || len(x) >= 2 && isNL(x[len(x)-1]) && isNL(x[len(x)-2])) { // x is empty or ends in blank line + y = y[1:] // delete y's leading blank line + } + return append(x, y...) +} + +func (p *printer) lineAt(start int) []byte { + pos := start + for pos < len(p.output) && !isNL(p.output[pos]) { + pos++ + } + if pos < len(p.output) { + pos++ + } + return p.output[start:pos] +} + +func (p *printer) commentTextAt(start int) string { + if start < len(p.output) && p.output[start] == tabwriter.Escape { + start++ + } + pos := start + for pos < len(p.output) && p.output[pos] != tabwriter.Escape && !isNL(p.output[pos]) { + pos++ + } + return string(p.output[start:pos]) +} + +func isNL(b byte) bool { + return b == '\n' || b == '\f' +} |