feat: Add flowCollectionPadding toString option (#420)

Author: cemerick

docs/03_options.md

@@ -157,6 +157,7 @@ Used by: `stringify()` and `doc.toString()`
 | doubleQuotedAsJSON             | `boolean`                                                                                 | `false`   | Restrict double-quoted strings to use JSON-compatible syntax.                                                                                                                                                                 |
 | doubleQuotedMinMultiLineLength | `number`                                                                                  | `40`      | Minimum length for double-quoted strings to use multiple lines to represent the value.                                                                                                                                        |
 | falseStr                       | `string`                                                                                  | `'false'` | String representation for `false` values.                                                                                                                                                                                     |
+| flowCollectionPadding          | `boolean`                                                                                 | `true`    | When true, a single space of padding will be added inside the delimiters of non-empty single-line flow collections.                                                                                                           |
 | indent                         | `number`                                                                                  | `2`       | The number of spaces to use when indenting code. Should be a strictly positive integer.                                                                                                                                       |
 | indentSeq                      | `boolean`                                                                                 | `true`    | Whether block sequences should be indented.                                                                                                                                                                                   |
 | lineWidth                      | `number`                                                                                  | `80`      | Maximum line width (set to `0` to disable folding). This is a soft limit, as only double-quoted semantics allow for inserting a line break in the middle of a word.                                                           |

src/options.ts

@@ -300,6 +300,14 @@ export type ToStringOptions = {
    */
   falseStr?: string
 
+  /**
+   * When true, a single space of padding will be added inside the delimiters
+   * of non-empty single-line flow collections.
+   * 
+   * Default: `true`
+   */
+  flowCollectionPadding?: boolean
+
   /**
    * The number of spaces to use when indenting code.
    *

src/stringify/stringify.ts

@@ -27,6 +27,7 @@ export type StringifyContext = {
   indentAtStart?: number
   inFlow: boolean | null
   inStringifyKey?: boolean
+  flowCollectionPadding: string
   options: Readonly<
     Required<Omit<ToStringOptions, 'collectionStyle' | 'indent'>>
   >
@@ -47,6 +48,7 @@ export function createStringifyContext(
       doubleQuotedAsJSON: false,
       doubleQuotedMinMultiLineLength: 40,
       falseStr: 'false',
+      flowCollectionPadding: true,
       indentSeq: true,
       lineWidth: 80,
       minContentWidth: 20,
@@ -75,6 +77,7 @@ export function createStringifyContext(
   return {
     anchors: new Set(),
     doc,
+    flowCollectionPadding: opt.flowCollectionPadding ? ' ' : '',
     indent: '',
     indentStep: typeof opt.indent === 'number' ? ' '.repeat(opt.indent) : '  ',
     inFlow,

src/stringify/stringifyCollection.ts

@@ -94,6 +94,7 @@ function stringifyFlowCollection(
   const {
     indent,
     indentStep,
+    flowCollectionPadding,
     options: { commentString }
   } = ctx
   itemIndent += indentStep
@@ -155,7 +156,7 @@ function stringifyFlowCollection(
         str += line ? `\n${indentStep}${indent}${line}` : '\n'
       str += `\n${indent}${end}`
     } else {
-      str = `${start} ${lines.join(' ')} ${end}`
+      str = `${start}${flowCollectionPadding}${lines.join(' ')}${flowCollectionPadding}${end}`
     }
   }
 

tests/doc/stringify.js

@@ -1180,3 +1180,17 @@ describe('YAML.stringify on ast Document', () => {
     expect(YAML.stringify(doc)).toBe('null\n')
   })
 })
+
+describe('flow collection padding', () => {
+  const doc = new YAML.Document();
+  doc.contents = new YAML.YAMLSeq();
+  doc.contents.items = [1, 2];
+  doc.contents.flow = true;
+
+  test('default', () => {
+    expect(doc.toString()).toBe('[ 1, 2 ]\n')
+  });
+  test('default', () => {
+    expect(doc.toString({flowCollectionPadding: false})).toBe('[1, 2]\n')
+  });
+})