| // Copyright 2019 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 diff supports a pluggable diff algorithm. |
| package diff |
| |
| import ( |
| "sort" |
| "strings" |
| |
| "golang.org/x/tools/internal/span" |
| ) |
| |
| // TextEdit represents a change to a section of a document. |
| // The text within the specified span should be replaced by the supplied new text. |
| type TextEdit struct { |
| Span span.Span |
| NewText string |
| } |
| |
| // ComputeEdits is the type for a function that produces a set of edits that |
| // convert from the before content to the after content. |
| type ComputeEdits func(uri span.URI, before, after string) []TextEdit |
| |
| // SortTextEdits attempts to order all edits by their starting points. |
| // The sort is stable so that edits with the same starting point will not |
| // be reordered. |
| func SortTextEdits(d []TextEdit) { |
| // Use a stable sort to maintain the order of edits inserted at the same position. |
| sort.SliceStable(d, func(i int, j int) bool { |
| return span.Compare(d[i].Span, d[j].Span) < 0 |
| }) |
| } |
| |
| // ApplyEdits applies the set of edits to the before and returns the resulting |
| // content. |
| // It may panic or produce garbage if the edits are not valid for the provided |
| // before content. |
| func ApplyEdits(before string, edits []TextEdit) string { |
| // Preconditions: |
| // - all of the edits apply to before |
| // - and all the spans for each TextEdit have the same URI |
| if len(edits) == 0 { |
| return before |
| } |
| edits = prepareEdits(edits) |
| c := span.NewContentConverter("", []byte(before)) |
| after := strings.Builder{} |
| last := 0 |
| for _, edit := range edits { |
| spn, _ := edit.Span.WithAll(c) |
| start := spn.Start().Offset() |
| if start > last { |
| after.WriteString(before[last:start]) |
| last = start |
| } |
| after.WriteString(edit.NewText) |
| last = spn.End().Offset() |
| } |
| if last < len(before) { |
| after.WriteString(before[last:]) |
| } |
| return after.String() |
| } |
| |
| // prepareEdits returns a sorted copy of the edits |
| func prepareEdits(edits []TextEdit) []TextEdit { |
| copied := make([]TextEdit, len(edits)) |
| copy(copied, edits) |
| SortTextEdits(copied) |
| return copied |
| } |