Add keepIndent option to toString

src/options.ts

@@ -329,6 +329,15 @@ export type ToStringOptions = {
    */
   indentSeq?: boolean
 
+  /**
+   * Whether indentation in srcToken should be preserved.
+   *
+   * For this to work, you need to have parsed the yaml document with keepSourceTokens: true
+   *
+   * Default: `false`
+   */
+  keepIndent?: boolean
+
   /**
    * Maximum line width (set to `0` to disable folding).
    *
@@ -387,4 +396,4 @@ export type ToStringOptions = {
    * Default: `'true'`
    */
   verifyAliasOrder?: boolean
-}
+}

src/stringify/stringify.ts

@@ -50,6 +50,7 @@ export function createStringifyContext(
       falseStr: 'false',
       flowCollectionPadding: true,
       indentSeq: true,
+      keepIndent: false,
       lineWidth: 80,
       minContentWidth: 20,
       nullStr: 'null',
@@ -175,4 +176,4 @@ export function stringify(
   return isScalar(node) || str[0] === '{' || str[0] === '['
     ? `${props} ${str}`
     : `${props}\n${ctx.indent}${str}`
-}
+}

src/stringify/stringifyPair.ts

@@ -15,9 +15,9 @@ export function stringifyPair(
     allNullValues,
     doc,
     indent,
-    indentStep,
-    options: { commentString, indentSeq, simpleKeys }
+    options: { commentString, indentSeq, keepIndent, simpleKeys }
   } = ctx
+
   let keyComment = (isNode(key) && key.comment) || null
   if (simpleKeys) {
     if (keyComment) {
@@ -37,6 +37,17 @@ export function stringifyPair(
         ? key.type === Scalar.BLOCK_FOLDED || key.type === Scalar.BLOCK_LITERAL
         : typeof key === 'object'))
 
+  let indentStep = ctx.indentStep
+  if (
+    keepIndent &&
+    isNode(value) &&
+    value.srcToken &&
+    'indent' in value.srcToken
+  ) {
+    const diff = value.srcToken.indent - indent.length
+    indentStep = ' '.repeat(diff)
+  }
+
   ctx = Object.assign({}, ctx, {
     allNullValues: false,
     implicitKey: !explicitKey && (simpleKeys || !allNullValues),
@@ -150,7 +161,8 @@ export function stringifyPair(
         }
         if (sp0 === -1 || nl0 < sp0) hasPropsLine = true
       }
-      if (!hasPropsLine) ws = `\n${ctx.indent}`
+      if (!hasPropsLine && (indentStep.length > 0 || !value.flow))
+        ws = `\n${ctx.indent}`
     }
   } else if (valueStr === '' || valueStr[0] === '\n') {
     ws = ''

tests/doc/stringify.ts

@@ -871,6 +871,128 @@ describe('custom indent', () => {
   })
 })
 
+describe('keepIndent: true', () => {
+  test('keep object indentation', () => {
+    const src = source`
+      key:
+              super: indented
+    `
+    const doc = YAML.parseDocument(src, { keepSourceTokens: true })
+    expect(doc.toString({ keepIndent: true })).toBe(src)
+  })
+
+  test('keep array indentation', () => {
+    const src = source`
+      key:
+      - name: foo
+      - name: bar
+      - name: bam
+      - name: baz
+    `
+    const doc = YAML.parseDocument(src, { keepSourceTokens: true })
+    expect(doc.toString({ keepIndent: true })).toBe(src)
+  })
+
+  test('keep complex indentation', () => {
+    const src = source`
+      key:
+              super:
+              - name: foo
+              - name: bar
+              - name: bam
+              - name: baz
+                metadata:
+                    foo: why
+    `
+    const doc = YAML.parseDocument(src, { keepSourceTokens: true })
+    expect(doc.toString({ keepIndent: true })).toBe(src)
+  })
+
+  test('handles multiline seq flow on same line', () => {
+    const src = source`
+      key: [
+        aaaaaaaa,
+        bbbbbbbb,
+        cccccccc,
+        dddddddd,
+        eeeeeeee,
+        ffffffff,
+        gggggggg,
+        hhhhhhhh
+      ]
+    `
+    const doc = YAML.parseDocument(src, { keepSourceTokens: true })
+    expect(doc.toString({ keepIndent: true })).toBe(src)
+  })
+  test('handles multiline flow on same line', () => {
+    const src = source`
+      key: !tag {
+        one: aaaaaaaa,
+        two: bbbbbbbb,
+        three: cccccccc,
+        four: dddddddd,
+        five: eeeeeeee
+      }
+    `
+    const doc = YAML.parseDocument(src, { keepSourceTokens: true })
+    expect(doc.toString({ keepIndent: true })).toBe(src)
+  })
+
+  test('handles multiline flow on next line', () => {
+    const src = source`
+      key:
+           !tag {
+             one: aaaaaaaa,
+             two: bbbbbbbb,
+             three: cccccccc,
+             four: dddddddd,
+             five: eeeeeeee
+           }
+    `
+    const doc = YAML.parseDocument(src, { keepSourceTokens: true })
+    expect(doc.toString({ keepIndent: true })).toBe(src)
+  })
+
+  test('handles multiline flow on next line', () => {
+    const src = source`
+      key:
+           !tag {
+             one: aaaaaaaa,
+             two: bbbbbbbb,
+             three: cccccccc,
+             four: dddddddd,
+             five: eeeeeeee
+           }
+    `
+    const doc = YAML.parseDocument(src, { keepSourceTokens: true })
+    expect(doc.toString({ keepIndent: true })).toBe(src)
+  })
+
+  test('handles explicit key map with no indent', () => {
+    const src = source`
+      foo:
+        ? [ key ]
+        : !tag
+        - foo
+        - bar
+    `
+    const doc = YAML.parseDocument(src, { keepSourceTokens: true })
+    expect(doc.toString({ keepIndent: true })).toBe(src)
+  })
+
+  test('handles explicit key map with indent', () => {
+    const src = source`
+      foo:
+          ? [ key ]
+          : !tag
+                - foo
+                - bar
+    `
+    const doc = YAML.parseDocument(src, { keepSourceTokens: true })
+    expect(doc.toString({ keepIndent: true })).toBe(src)
+  })
+})
+
 describe('indentSeq: false', () => {
   let obj: unknown
   beforeEach(() => {