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Cleanup edit groups after coalescing #259
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Original file line number | Diff line number | Diff line change |
---|---|---|
|
@@ -338,8 +338,11 @@ func (opts formatOptions) formatDiffSlice( | |
vx, vy reflect.Value, chunkSize int, name string, | ||
makeRec func(reflect.Value, diffMode) textRecord, | ||
) (list textList) { | ||
es := diff.Difference(vx.Len(), vy.Len(), func(ix int, iy int) diff.Result { | ||
return diff.BoolResult(vx.Index(ix).Interface() == vy.Index(iy).Interface()) | ||
eq := func(ix, iy int) bool { | ||
return vx.Index(ix).Interface() == vy.Index(iy).Interface() | ||
} | ||
es := diff.Difference(vx.Len(), vy.Len(), func(ix, iy int) diff.Result { | ||
return diff.BoolResult(eq(ix, iy)) | ||
}) | ||
|
||
appendChunks := func(v reflect.Value, d diffMode) int { | ||
|
@@ -364,6 +367,7 @@ func (opts formatOptions) formatDiffSlice( | |
|
||
groups := coalesceAdjacentEdits(name, es) | ||
groups = coalesceInterveningIdentical(groups, chunkSize/4) | ||
groups = cleanupSurroundingIdentical(groups, eq) | ||
maxGroup := diffStats{Name: name} | ||
for i, ds := range groups { | ||
if maxLen >= 0 && numDiffs >= maxLen { | ||
|
@@ -416,25 +420,36 @@ func (opts formatOptions) formatDiffSlice( | |
|
||
// coalesceAdjacentEdits coalesces the list of edits into groups of adjacent | ||
// equal or unequal counts. | ||
// | ||
// Example: | ||
// | ||
// Input: "..XXY...Y" | ||
// Output: [ | ||
// {NumIdentical: 2}, | ||
// {NumRemoved: 2, NumInserted 1}, | ||
// {NumIdentical: 3}, | ||
// {NumInserted: 1}, | ||
// ] | ||
// | ||
func coalesceAdjacentEdits(name string, es diff.EditScript) (groups []diffStats) { | ||
var prevCase int // Arbitrary index into which case last occurred | ||
lastStats := func(i int) *diffStats { | ||
if prevCase != i { | ||
var prevMode byte | ||
lastStats := func(mode byte) *diffStats { | ||
if prevMode != mode { | ||
groups = append(groups, diffStats{Name: name}) | ||
prevCase = i | ||
prevMode = mode | ||
} | ||
return &groups[len(groups)-1] | ||
} | ||
for _, e := range es { | ||
switch e { | ||
case diff.Identity: | ||
lastStats(1).NumIdentical++ | ||
lastStats('=').NumIdentical++ | ||
case diff.UniqueX: | ||
lastStats(2).NumRemoved++ | ||
lastStats('!').NumRemoved++ | ||
case diff.UniqueY: | ||
lastStats(2).NumInserted++ | ||
lastStats('!').NumInserted++ | ||
case diff.Modified: | ||
lastStats(2).NumModified++ | ||
lastStats('!').NumModified++ | ||
} | ||
} | ||
return groups | ||
|
@@ -444,6 +459,35 @@ func coalesceAdjacentEdits(name string, es diff.EditScript) (groups []diffStats) | |
// equal groups into adjacent unequal groups that currently result in a | ||
// dual inserted/removed printout. This acts as a high-pass filter to smooth | ||
// out high-frequency changes within the windowSize. | ||
// | ||
// Example: | ||
// | ||
// WindowSize: 16, | ||
// Input: [ | ||
// {NumIdentical: 61}, // group 0 | ||
// {NumRemoved: 3, NumInserted: 1}, // group 1 | ||
// {NumIdentical: 6}, // ├── coalesce | ||
// {NumInserted: 2}, // ├── coalesce | ||
// {NumIdentical: 1}, // ├── coalesce | ||
// {NumRemoved: 9}, // └── coalesce | ||
// {NumIdentical: 64}, // group 2 | ||
// {NumRemoved: 3, NumInserted: 1}, // group 3 | ||
// {NumIdentical: 6}, // ├── coalesce | ||
// {NumInserted: 2}, // ├── coalesce | ||
// {NumIdentical: 1}, // ├── coalesce | ||
// {NumRemoved: 7}, // ├── coalesce | ||
// {NumIdentical: 1}, // ├── coalesce | ||
// {NumRemoved: 2}, // └── coalesce | ||
// {NumIdentical: 63}, // group 4 | ||
// ] | ||
// Output: [ | ||
// {NumIdentical: 61}, | ||
// {NumIdentical: 7, NumRemoved: 12, NumInserted: 3}, | ||
// {NumIdentical: 64}, | ||
// {NumIdentical: 8, NumRemoved: 12, NumInserted: 3}, | ||
// {NumIdentical: 63}, | ||
// ] | ||
// | ||
func coalesceInterveningIdentical(groups []diffStats, windowSize int) []diffStats { | ||
groups, groupsOrig := groups[:0], groups | ||
for i, ds := range groupsOrig { | ||
|
@@ -463,3 +507,91 @@ func coalesceInterveningIdentical(groups []diffStats, windowSize int) []diffStat | |
} | ||
return groups | ||
} | ||
|
||
// cleanupSurroundingIdentical scans through all unequal groups, and | ||
// moves any leading sequence of equal elements to the preceding equal group and | ||
// moves and trailing sequence of equal elements to the succeeding equal group. | ||
// | ||
// This is necessary since coalesceInterveningIdentical may coalesce edit groups | ||
// together such that leading/trailing spans of equal elements becomes possible. | ||
// Note that this can occur even with an optimal diffing algorithm. | ||
// | ||
// Example: | ||
// | ||
// Input: [ | ||
// {NumIdentical: 61}, | ||
// {NumIdentical: 1 , NumRemoved: 11, NumInserted: 2}, // assume 3 leading identical elements | ||
// {NumIdentical: 67}, | ||
// {NumIdentical: 7, NumRemoved: 12, NumInserted: 3}, // assume 10 trailing identical elements | ||
// {NumIdentical: 54}, | ||
// ] | ||
// Output: [ | ||
// {NumIdentical: 64}, // incremented by 3 | ||
// {NumRemoved: 9}, | ||
// {NumIdentical: 67}, | ||
// {NumRemoved: 9}, | ||
// {NumIdentical: 64}, // incremented by 10 | ||
// ] | ||
// | ||
func cleanupSurroundingIdentical(groups []diffStats, eq func(i, j int) bool) []diffStats { | ||
var ix, iy int // indexes into sequence x and y | ||
for i, ds := range groups { | ||
// Handle equal group. | ||
if ds.NumDiff() == 0 { | ||
ix += ds.NumIdentical | ||
iy += ds.NumIdentical | ||
continue | ||
} | ||
|
||
// Handle unequal group. | ||
nx := ds.NumIdentical + ds.NumRemoved + ds.NumModified | ||
ny := ds.NumIdentical + ds.NumInserted + ds.NumModified | ||
var numLeadingIdentical, numTrailingIdentical int | ||
for i := 0; i < nx && i < ny && eq(ix+i, iy+i); i++ { | ||
numLeadingIdentical++ | ||
} | ||
for i := 0; i < nx && i < ny && eq(ix+nx-1-i, iy+ny-1-i); i++ { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Same |
||
numTrailingIdentical++ | ||
} | ||
if numIdentical := numLeadingIdentical + numTrailingIdentical; numIdentical > 0 { | ||
if numLeadingIdentical > 0 { | ||
// Remove leading identical span from this group and | ||
// insert it into the preceding group. | ||
if i-1 >= 0 { | ||
groups[i-1].NumIdentical += numLeadingIdentical | ||
} else { | ||
// No preceding group exists, so prepend a new group, | ||
// but do so after we finish iterating over all groups. | ||
defer func() { | ||
groups = append([]diffStats{{Name: groups[0].Name, NumIdentical: numLeadingIdentical}}, groups...) | ||
}() | ||
} | ||
// Increment indexes since the preceding group would have handled this. | ||
ix += numLeadingIdentical | ||
iy += numLeadingIdentical | ||
} | ||
if numTrailingIdentical > 0 { | ||
// Remove trailing identical span from this group and | ||
// insert it into the succeeding group. | ||
if i+1 < len(groups) { | ||
groups[i+1].NumIdentical += numTrailingIdentical | ||
} else { | ||
// No succeeding group exists, so append a new group, | ||
// but do so after we finish iterating over all groups. | ||
defer func() { | ||
groups = append(groups, diffStats{Name: groups[len(groups)-1].Name, NumIdentical: numTrailingIdentical}) | ||
}() | ||
} | ||
// Do not increment indexes since the succeeding group will handle this. | ||
} | ||
|
||
// Update this group since some identical elements were removed. | ||
nx -= numIdentical | ||
ny -= numIdentical | ||
groups[i] = diffStats{Name: ds.Name, NumRemoved: nx, NumInserted: ny} | ||
} | ||
ix += nx | ||
iy += ny | ||
} | ||
return groups | ||
} |
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The shadowing of
i
is not helping with readability.