Use yaml package for formatting

This replaces Prettier as the LSP formatting solution with the `yaml`
package. The `yaml` package can format YAML just fine, and we already
have it as a dependency. Prettier is a big dependency.

If people want to use Prettier, other Prettier integrations are probably
better suited for them. For example, the YAML language server doesn’t
respect Prettier configuration files.

This is a proof of concept. I tried to map existing options to the new
implementation. A more ideal solution might be to change the formatting
options.

Refs #933

Author: remcohaszing

package-lock.json

@@ -30,7 +30,6 @@
     "@vscode/l10n": "^0.0.18",
     "ajv": "^8.17.1",
     "ajv-draft-04": "^1.0.0",
-    "prettier": "^3.8.1",
     "request-light": "^0.5.7",
     "vscode-json-languageservice": "4.1.8",
     "vscode-languageserver": "^9.0.0",
@@ -56,6 +55,7 @@
     "mocha": "11.7.1",
     "mocha-lcov-reporter": "^1.3.0",
     "nyc": "^15.1.0",
+    "prettier": "3.8.1",
     "rimraf": "^3.0.2",
     "sinon": "^9.0.3",
     "sinon-chai": "^3.5.0",

package.json

@@ -106,7 +106,6 @@ export class SettingsHandler {
 
       if (settings.yaml.format) {
         this.yamlSettings.yamlFormatterSettings = {
-          proseWrap: settings.yaml.format.proseWrap || 'preserve',
           printWidth: settings.yaml.format.printWidth || 80,
         };
 

src/languageserver/handlers/settingsHandlers.ts

@@ -4,20 +4,23 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
-import { Range, Position, TextEdit, FormattingOptions } from 'vscode-languageserver-types';
-import { CustomFormatterOptions, LanguageSettings } from '../yamlLanguageService';
-import { Options } from 'prettier';
-import * as yamlPlugin from 'prettier/plugins/yaml';
-import * as estreePlugin from 'prettier/plugins/estree';
-import { format } from 'prettier/standalone';
 import { TextDocument } from 'vscode-languageserver-textdocument';
+import { FormattingOptions, Position, Range, TextEdit } from 'vscode-languageserver-types';
+import { parseDocument, ToStringOptions } from 'yaml';
+import { YamlVersion } from '../parser/yamlParser07';
+import { CustomFormatterOptions, LanguageSettings } from '../yamlLanguageService';
+import { getCustomTags } from '../parser/custom-tag-provider';
 
 export class YAMLFormatter {
   private formatterEnabled = true;
+  private yamlVersion: YamlVersion = '1.2';
+  private customTags: string[] = [];
 
   public configure(shouldFormat: LanguageSettings): void {
     if (shouldFormat) {
       this.formatterEnabled = shouldFormat.format;
+      this.yamlVersion = shouldFormat.yamlVersion;
+      this.customTags = shouldFormat.customTags;
     }
   }
 
@@ -31,24 +34,28 @@ export class YAMLFormatter {
 
     try {
       const text = document.getText();
+      const doc = parseDocument(text, {
+        version: this.yamlVersion,
+        customTags: getCustomTags(this.customTags),
+      });
 
-      const prettierOptions: Options = {
-        parser: 'yaml',
-        plugins: [yamlPlugin, estreePlugin],
-
+      const toStringOptions: ToStringOptions = {
         // --- FormattingOptions ---
-        tabWidth: (options.tabWidth as number) || options.tabSize,
+        indent: (options.tabWidth as number) || options.tabSize || 2,
 
         // --- CustomFormatterOptions ---
         singleQuote: options.singleQuote,
-        bracketSpacing: options.bracketSpacing,
-        // 'preserve' is the default for Options.proseWrap. See also server.ts
-        proseWrap: 'always' === options.proseWrap ? 'always' : 'never' === options.proseWrap ? 'never' : 'preserve',
-        printWidth: options.printWidth,
-        trailingComma: options.trailingComma === false ? 'none' : 'all',
+        flowCollectionPadding: options.bracketSpacing,
+        blockQuote: options.proseWrap === 'always' ? 'folded' : true,
+        lineWidth: Math.max(options.printWidth || 0, 22),
+        trailingComma: options.trailingComma === undefined ? true : options.trailingComma,
       };
 
-      const formatted = await format(text, prettierOptions);
+      const formatted = doc.toString(toStringOptions);
+
+      if (formatted === text) {
+        return [];
+      }
 
       return [TextEdit.replace(Range.create(Position.create(0, 0), document.positionAt(text.length)), formatted)];
     } catch (error) {

src/languageservice/services/yamlFormatter.ts

@@ -86,7 +86,19 @@ describe('Formatter Tests', () => {
           printWidth: 20,
           proseWrap: 'always',
         });
-        assert.equal(edits[0].newText, 'comments: >\n  test test test\n  test test test\n  test test test\n  test test test\n');
+        assert.equal(edits[0].newText, 'comments: >\n  test test test test\n  test test test test\n  test test test test\n');
+      });
+
+      it('Formatting handles trailing commas (default)', async () => {
+        const content = `{
+  key: 'value',
+  food: 'raisins',
+  airport: 'YYZ',
+  lightened_bulb: 'illuminating',
+}
+`;
+        const edits = await parseSetup(content, { singleQuote: true, trailingComma: true });
+        assert.equal(edits.length, 0);
       });
 
       it('Formatting handles trailing commas (enabled)', async () => {
@@ -98,7 +110,7 @@ describe('Formatter Tests', () => {
 }
 `;
         const edits = await parseSetup(content, { singleQuote: true });
-        assert.equal(edits[0].newText, content);
+        assert.equal(edits.length, 0);
       });
 
       it('Formatting handles trailing commas (disabled)', async () => {