Invert string diffs

Allows formatting strings nested inside items, mapEntries, and
properties.

Fixes #40.

lib/diff.js

@@ -304,7 +304,7 @@ function diffDescriptors (lhs, rhs, options) {
         topIndex++
       } else {
         const diffed = typeof lhs.diffDeep === 'function'
-          ? lhs.diffDeep(rhs, themeUtils.applyModifiers(lhs, theme), indent)
+          ? lhs.diffDeep(rhs, themeUtils.applyModifiers(lhs, theme), indent, invert)
           : null
 
         if (diffed === null) {

lib/metaDescriptors/item.js

@@ -227,7 +227,7 @@ class PrimitiveItem {
     } while (true)
   }
 
-  diffDeep (expected, theme, indent) {
+  diffDeep (expected, theme, indent, invert) {
     // Verify a diff can be returned.
     if (this.tag !== expected.tag || typeof this.value.diffDeep !== 'function') return null
 
@@ -236,7 +236,7 @@ class PrimitiveItem {
 
     // Since the value is diffed directly, modifiers are not applied. Apply
     // modifiers to the item descriptor instead.
-    const diff = this.value.diffDeep(expected.value, theme, valueIndent)
+    const diff = this.value.diffDeep(expected.value, theme, valueIndent, invert)
     if (diff === null) return null
 
     if (typeof theme.item.customFormat === 'function') {

lib/metaDescriptors/mapEntry.js

@@ -117,7 +117,7 @@ class MapEntry {
     }
   }
 
-  diffDeep (expected, theme, indent) {
+  diffDeep (expected, theme, indent, invert) {
     // Verify a diff can be returned.
     if (this.tag !== expected.tag || typeof this.value.diffDeep !== 'function') return null
     // Only use this logic to format value diffs when the keys are primitive and equal.
@@ -127,7 +127,7 @@ class MapEntry {
 
     // Since formatShallow() would result in theme modifiers being applied
     // before the key and value are formatted, do the same here.
-    const diff = this.value.diffDeep(expected.value, themeUtils.applyModifiersToOriginal(this.value, theme), indent)
+    const diff = this.value.diffDeep(expected.value, themeUtils.applyModifiersToOriginal(this.value, theme), indent, invert)
     if (diff === null) return null
 
     const key = this.key.formatDeep(themeUtils.applyModifiersToOriginal(this.key, theme), indent, '')

lib/metaDescriptors/property.js

@@ -160,7 +160,7 @@ class PrimitiveProperty extends Property {
       .withLastPostfixed(theme.property.after)
   }
 
-  diffDeep (expected, theme, indent) {
+  diffDeep (expected, theme, indent, invert) {
     // Verify a diff can be returned.
     if (this.tag !== expected.tag || typeof this.value.diffDeep !== 'function') return null
     // Only use this logic to diff values when the keys are the same.
@@ -171,7 +171,7 @@ class PrimitiveProperty extends Property {
 
     // Since the key and value are diffed directly, modifiers are not
     // applied. Apply modifiers to the property descriptor instead.
-    const diff = this.value.diffDeep(expected.value, theme, valueIndent)
+    const diff = this.value.diffDeep(expected.value, theme, valueIndent, invert)
     if (diff === null) return null
 
     if (typeof theme.property.customFormat === 'function') {

lib/primitiveValues/string.js

@@ -61,7 +61,7 @@ function includesLinebreaks (string) {
   return string.includes('\r') || string.includes('\n')
 }
 
-function diffLine (theme, actual, expected) {
+function diffLine (theme, actual, expected, invert) {
   const outcome = fastDiff(actual, expected)
 
   // TODO: Compute when line is mostly unequal (80%? 90%?) and treat it as being
@@ -83,9 +83,14 @@ function diffLine (theme, actual, expected) {
   let stringExpected = ''
 
   const noopWrap = { open: '', close: '' }
-  const deleteWrap = isPartiallyEqual ? theme.string.diff.delete : noopWrap
-  const insertWrap = isPartiallyEqual ? theme.string.diff.insert : noopWrap
+  let deleteWrap = isPartiallyEqual ? theme.string.diff.delete : noopWrap
+  let insertWrap = isPartiallyEqual ? theme.string.diff.insert : noopWrap
   const equalWrap = isPartiallyEqual ? theme.string.diff.equal : noopWrap
+
+  if (invert) {
+    [deleteWrap, insertWrap] = [insertWrap, deleteWrap]
+  }
+
   for (const diff of outcome) {
     if (diff[0] === fastDiff.DELETE) {
       stringActual += formatUtils.wrap(deleteWrap, diff[1])
@@ -99,8 +104,11 @@ function diffLine (theme, actual, expected) {
   }
 
   if (!isPartiallyEqual) {
-    stringActual = formatUtils.wrap(theme.string.diff.deleteLine, stringActual)
-    stringExpected = formatUtils.wrap(theme.string.diff.insertLine, stringExpected)
+    const deleteLineWrap = invert ? theme.string.diff.insertLine : theme.string.diff.deleteLine
+    const insertLineWrap = invert ? theme.string.diff.deleteLine : theme.string.diff.insertLine
+
+    stringActual = formatUtils.wrap(deleteLineWrap, stringActual)
+    stringExpected = formatUtils.wrap(insertLineWrap, stringExpected)
   }
 
   return [stringActual, stringExpected]
@@ -170,7 +178,7 @@ class StringValue {
     return formatUtils.wrap(theme.string.line, formatUtils.wrap(theme.string, escaped))
   }
 
-  diffDeep (expected, theme, indent) {
+  diffDeep (expected, theme, indent, invert) {
     if (expected.tag !== tag) return null
 
     const escapedActual = basicEscape(this.value)
@@ -179,7 +187,9 @@ class StringValue {
     if (!includesLinebreaks(escapedActual) && !includesLinebreaks(escapedExpected)) {
       const result = diffLine(theme,
         escapeQuotes(theme.string.line, escapedActual),
-        escapeQuotes(theme.string.line, escapedExpected))
+        escapeQuotes(theme.string.line, escapedExpected),
+        invert,
+      )
 
       return lineBuilder.actual.single(formatUtils.wrap(theme.string.line, result[0]))
         .concat(lineBuilder.expected.single(formatUtils.wrap(theme.string.line, result[1])))
@@ -241,7 +251,8 @@ class StringValue {
       }
 
       if (actualIsExtraneous && !expectedIsMissing) {
-        const string = formatUtils.wrap(theme.string.diff.deleteLine, actualLines[actualIndex])
+        const wrap = invert ? theme.string.diff.insertLine : theme.string.diff.deleteLine
+        const string = formatUtils.wrap(wrap, actualLines[actualIndex])
 
         if (actualIndex === 0) {
           actualBuffer.push(lineBuilder.actual.first(theme.string.multiline.start + string))
@@ -255,7 +266,8 @@ class StringValue {
         actualIndex++
         extraneousOffset++
       } else if (expectedIsMissing && !actualIsExtraneous) {
-        const string = formatUtils.wrap(theme.string.diff.insertLine, expectedLines[expectedIndex])
+        const wrap = invert ? theme.string.diff.deleteLine : theme.string.diff.insertLine
+        const string = formatUtils.wrap(wrap, expectedLines[expectedIndex])
 
         if (mustOpenNextExpected) {
           expectedBuffer.push(lineBuilder.expected.first(theme.string.multiline.start + string))
@@ -268,7 +280,7 @@ class StringValue {
 
         expectedIndex++
       } else {
-        const result = diffLine(theme, actualLines[actualIndex], expectedLines[expectedIndex])
+        const result = diffLine(theme, actualLines[actualIndex], expectedLines[expectedIndex], invert)
 
         if (actualIndex === 0) {
           actualBuffer.push(lineBuilder.actual.first(theme.string.multiline.start + result[0]))

test/diff.js

@@ -487,6 +487,25 @@ test('inverted diffs', t => {
   }, { invert: true }))
 })
 
+test('inverts string diffs', t => {
+  t.snapshot(diff('foo', 'bar', { invert: true }))
+  t.snapshot(diff('foo bar baz', 'foo baz quux', { invert: true }))
+  t.snapshot(diff('foo\nbar\nbaz', 'foobarbaz', { invert: true }))
+})
+
+test('inverts string diffs in containers', t => {
+  const actual = 'foo\nbar\nbaz'
+  const expected = 'foo\nbaz\nquux'
+
+  t.snapshot(diff({ a: actual }, { a: expected }, { invert: true }))
+  t.snapshot(diff([actual], [expected], { invert: true }))
+  t.snapshot(diff(new Map().set('a', actual), new Map().set('a', expected), { invert: true }))
+  t.snapshot(diff(new Set().add(actual), new Set().add(expected), { invert: true }))
+  t.snapshot(diff(new String(actual), new String(expected), { invert: true })) // eslint-disable-line unicorn/new-for-builtins, no-new-wrappers
+
+  t.snapshot(diff({ a: { b: actual } }, { a: { b: expected } }, { invert: true }))
+})
+
 test('lists: effectively resets depth when formatting differences', t => {
   const l1 = [
     {

test/snapshots/diff.js.md

@@ -1139,12 +1139,95 @@ Generated by [AVA](https://avajs.dev).
 
     `%diffGutters.padding#  %%object.openBracket#{%␊
     %diffGutters.padding#  %  baz%property.separator#: %%string.multiline.start#`%%string.diff.equal.open%qux%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
-    %diffGutters.actual#- %  %string.diff.insertLine.open%corge%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.insertLine.close%␊
-    %diffGutters.actual#- %  %string.diff.insertLine.open%quux%string.diff.insertLine.close%%string.multiline.end#`%%property.after#,%␊
-    %diffGutters.expected#+ %  %string.diff.deleteLine.open%quux%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.deleteLine.close%␊
-    %diffGutters.expected#+ %  %string.diff.deleteLine.open%corge%string.diff.deleteLine.close%%string.multiline.end#`%%property.after#,%␊
-    %diffGutters.actual#- %  foo%property.separator#: %%string.line.open#'%%string.diff.insertLine.open%BAR%string.diff.insertLine.close%%string.line.close#'%%property.after#,%␊
-    %diffGutters.expected#+ %  foo%property.separator#: %%string.line.open#'%%string.diff.deleteLine.open%bar%string.diff.deleteLine.close%%string.line.close#'%%property.after#,%␊
+    %diffGutters.actual#- %  %string.diff.deleteLine.open%corge%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.deleteLine.close%␊
+    %diffGutters.actual#- %  %string.diff.deleteLine.open%quux%string.diff.deleteLine.close%%string.multiline.end#`%%property.after#,%␊
+    %diffGutters.expected#+ %  %string.diff.insertLine.open%quux%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.insertLine.close%␊
+    %diffGutters.expected#+ %  %string.diff.insertLine.open%corge%string.diff.insertLine.close%%string.multiline.end#`%%property.after#,%␊
+    %diffGutters.actual#- %  foo%property.separator#: %%string.line.open#'%%string.diff.deleteLine.open%BAR%string.diff.deleteLine.close%%string.line.close#'%%property.after#,%␊
+    %diffGutters.expected#+ %  foo%property.separator#: %%string.line.open#'%%string.diff.insertLine.open%bar%string.diff.insertLine.close%%string.line.close#'%%property.after#,%␊
+    %diffGutters.padding#  %%object.closeBracket#}%`
+
+## inverts string diffs
+
+> Snapshot 1
+
+    `%diffGutters.actual#- %%string.line.open#'%%string.diff.deleteLine.open%bar%string.diff.deleteLine.close%%string.line.close#'%␊
+    %diffGutters.expected#+ %%string.line.open#'%%string.diff.insertLine.open%foo%string.diff.insertLine.close%%string.line.close#'%`
+
+> Snapshot 2
+
+    `%diffGutters.actual#- %%string.line.open#'%%string.diff.equal.open%foo ba%string.diff.equal.close%%string.diff.delete.open%z%string.diff.delete.close%%string.diff.equal.open% %string.diff.equal.close%%string.diff.delete.open%quux%string.diff.delete.close%%string.line.close#'%␊
+    %diffGutters.expected#+ %%string.line.open#'%%string.diff.equal.open%foo ba%string.diff.equal.close%%string.diff.insert.open%r%string.diff.insert.close%%string.diff.equal.open% %string.diff.equal.close%%string.diff.insert.open%baz%string.diff.insert.close%%string.line.close#'%`
+
+> Snapshot 3
+
+    `%diffGutters.actual#- %%string.multiline.start#`%%string.diff.delete.open%foobar%string.diff.delete.close%%string.diff.equal.open%baz%string.diff.equal.close%␊
+    %diffGutters.expected#+ %%string.multiline.start#`%%string.diff.insertLine.open%foo␊%string.diff.insertLine.close%␊
+    %diffGutters.expected#+ %%string.diff.insertLine.open%bar␊%string.diff.insertLine.close%␊
+    %diffGutters.expected#+ %%string.diff.equal.open%baz%string.diff.equal.close%%string.multiline.end#`%`
+
+## inverts string diffs in containers
+
+> Snapshot 1
+
+    `%diffGutters.padding#  %%object.openBracket#{%␊
+    %diffGutters.padding#  %  a%property.separator#: %%string.multiline.start#`%%string.diff.equal.open%foo%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.delete.open%z%string.diff.delete.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.deleteLine.open%quux%string.diff.deleteLine.close%%string.multiline.end#`%%property.after#,%␊
+    %diffGutters.expected#+ %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.insert.open%r%string.diff.insert.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.expected#+ %  %string.diff.insertLine.open%baz%string.diff.insertLine.close%%string.multiline.end#`%%property.after#,%␊
+    %diffGutters.padding#  %%object.closeBracket#}%`
+
+> Snapshot 2
+
+    `%diffGutters.padding#  %%list.openBracket#[%␊
+    %diffGutters.padding#  %  %string.multiline.start#`%%string.diff.equal.open%foo%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.delete.open%z%string.diff.delete.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.deleteLine.open%quux%string.diff.deleteLine.close%%string.multiline.end#`%%item.after#,%␊
+    %diffGutters.expected#+ %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.insert.open%r%string.diff.insert.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.expected#+ %  %string.diff.insertLine.open%baz%string.diff.insertLine.close%%string.multiline.end#`%%item.after#,%␊
+    %diffGutters.padding#  %%list.closeBracket#]%`
+
+> Snapshot 3
+
+    `%diffGutters.padding#  %%object.ctor.open%Map%object.ctor.close% %object.openBracket#{%␊
+    %diffGutters.padding#  %  %string.line.open#'%%string.open%a%string.close%%string.line.close#'%%mapEntry.separator# => %%string.multiline.start#`%%string.diff.equal.open%foo%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.delete.open%z%string.diff.delete.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.deleteLine.open%quux%string.diff.deleteLine.close%%string.multiline.end#`%%mapEntry.after#,%␊
+    %diffGutters.expected#+ %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.insert.open%r%string.diff.insert.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.expected#+ %  %string.diff.insertLine.open%baz%string.diff.insertLine.close%%string.multiline.end#`%%mapEntry.after#,%␊
+    %diffGutters.padding#  %%object.closeBracket#}%`
+
+> Snapshot 4
+
+    `%diffGutters.padding#  %%object.ctor.open%Set%object.ctor.close% %object.openBracket#{%␊
+    %diffGutters.padding#  %  %string.multiline.start#`%%string.diff.equal.open%foo%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.delete.open%z%string.diff.delete.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.deleteLine.open%quux%string.diff.deleteLine.close%%string.multiline.end#`%%item.after#,%␊
+    %diffGutters.expected#+ %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.insert.open%r%string.diff.insert.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.expected#+ %  %string.diff.insertLine.open%baz%string.diff.insertLine.close%%string.multiline.end#`%%item.after#,%␊
+    %diffGutters.padding#  %%object.closeBracket#}%`
+
+> Snapshot 5
+
+    `%diffGutters.padding#  %%object.ctor.open%String%object.ctor.close% %object.openBracket#{%␊
+    %diffGutters.padding#  %  %string.multiline.start#`%%string.diff.equal.open%foo%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.delete.open%z%string.diff.delete.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %  %string.diff.deleteLine.open%quux%string.diff.deleteLine.close%%string.multiline.end#`%␊
+    %diffGutters.expected#+ %  %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.insert.open%r%string.diff.insert.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.expected#+ %  %string.diff.insertLine.open%baz%string.diff.insertLine.close%%string.multiline.end#`%␊
+    %diffGutters.padding#  %%object.closeBracket#}%`
+
+> Snapshot 6
+
+    `%diffGutters.padding#  %%object.openBracket#{%␊
+    %diffGutters.padding#  %  a%property.separator#: %%object.openBracket#{%␊
+    %diffGutters.padding#  %    b%property.separator#: %%string.multiline.start#`%%string.diff.equal.open%foo%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %    %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.delete.open%z%string.diff.delete.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.actual#- %    %string.diff.deleteLine.open%quux%string.diff.deleteLine.close%%string.multiline.end#`%%property.after#,%␊
+    %diffGutters.expected#+ %    %string.diff.equal.open%ba%string.diff.equal.close%%string.diff.insert.open%r%string.diff.insert.close%%string.diff.equal.open%%string.diff.equal.close%%string.controlPicture.open%␊%string.controlPicture.close%%string.diff.equal.open%%string.diff.equal.close%␊
+    %diffGutters.expected#+ %    %string.diff.insertLine.open%baz%string.diff.insertLine.close%%string.multiline.end#`%%property.after#,%␊
+    %diffGutters.padding#  %  %object.closeBracket#}%%property.after#,%␊
     %diffGutters.padding#  %%object.closeBracket#}%`
 
 ## lists: effectively resets depth when formatting differences