(fix) resolve plugin config for prettier

packages/language-server/src/plugins/svelte/SveltePlugin.ts

@@ -1,3 +1,4 @@
+import { isAbsolute } from 'path';
 import {
     CancellationToken,
     CodeAction,
@@ -17,6 +18,7 @@ import { getPackageInfo, importPrettier } from '../../importPackage';
 import { Document } from '../../lib/documents';
 import { Logger } from '../../logger';
 import { LSConfigManager, LSSvelteConfig } from '../../ls-config';
+import { isNotNullOrUndefined } from '../../utils';
 import {
     CodeActionsProvider,
     CompletionsProvider,
@@ -106,7 +108,14 @@ export class SveltePlugin
 
         const formattedCode = prettier.format(document.getText(), {
             ...config,
-            plugins: [...(config.plugins ?? []), ...getSveltePlugin()],
+            plugins: Array.from(
+                new Set([
+                    ...((config.plugins as string[]) ?? [])
+                        .map(resolvePlugin)
+                        .filter(isNotNullOrUndefined),
+                    ...getSveltePlugin()
+                ])
+            ),
             parser: 'svelte' as any
         });
 
@@ -132,6 +141,21 @@ export class SveltePlugin
                 .languages.some((l) => l.name === 'svelte');
             return hasPluginLoadedAlready ? [] : [require.resolve('prettier-plugin-svelte')];
         }
+
+        function resolvePlugin(plugin: string) {
+            // https://github.com/prettier/prettier-vscode/blob/160b0e92d88fa19003dce2745d5ab8c67e886a04/src/ModuleResolver.ts#L373
+            if (typeof plugin != 'string' || isAbsolute(plugin) || plugin.startsWith('.')) {
+                return plugin;
+            }
+
+            try {
+                return require.resolve(plugin, {
+                    paths: [filePath]
+                });
+            } catch (error) {
+                Logger.error(`failed to resolve plugin ${plugin} with error:\n`, error);
+            }
+        }
     }
 
     async getCompletions(

packages/language-server/test/plugins/svelte/SveltePlugin.test.ts

@@ -10,10 +10,16 @@ import {
 import { LSConfigManager } from '../../../src/ls-config';
 import * as importPackage from '../../../src/importPackage';
 import sinon from 'sinon';
+import { join } from 'path';
+import { pathToUrl, urlToPath } from '../../../src/utils';
 
 describe('Svelte Plugin', () => {
-    function setup(content: string, prettierConfig?: any, trusted = true) {
-        const document = new Document('file:///hello.svelte', content);
+    function setup(
+        content: string,
+        prettierConfig?: any,
+        { trusted = true, documentUri = 'file:///hello.svelte' } = {}
+    ) {
+        const document = new Document(documentUri, content);
         const docManager = new DocumentManager(() => document);
         const pluginManager = new LSConfigManager();
         pluginManager.updateIsTrusted(trusted);
@@ -54,7 +60,7 @@ describe('Svelte Plugin', () => {
     });
 
     it('provides no diagnostic errors when untrusted', async () => {
-        const { plugin, document } = setup('<div bind:whatever></div>', {}, false);
+        const { plugin, document } = setup('<div bind:whatever></div>', {}, { trusted: false });
 
         const diagnostics = await plugin.getDiagnostics(document);
 
@@ -75,8 +81,12 @@ describe('Svelte Plugin', () => {
             return formatStub;
         }
 
-        async function testFormat(config: any, fallbackPrettierConfig: any) {
-            const { plugin, document } = setup('unformatted', fallbackPrettierConfig);
+        async function testFormat(
+            config: any,
+            fallbackPrettierConfig: any,
+            options?: Parameters<typeof setup>[2]
+        ) {
+            const { plugin, document } = setup('unformatted', fallbackPrettierConfig, options);
             const formatStub = stubPrettier(config);
 
             const formatted = await plugin.formatDocument(document, {
@@ -115,6 +125,22 @@ describe('Svelte Plugin', () => {
             });
         });
 
+        it('can resolve plugin for formatting', async () => {
+            const documentUri = pathToUrl(join(__dirname, 'testFiles', 'do-not-exist.svelte'));
+            const formatStub = await testFormat(
+                { fromConfig: true, plugins: ['prettier-plugin-svelte'] },
+                { fallbackConfig: true },
+                { documentUri }
+            );
+            sinon.assert.calledOnceWithExactly(formatStub, 'unformatted', {
+                fromConfig: true,
+                plugins: [
+                    require.resolve('prettier-plugin-svelte', { paths: [urlToPath(documentUri)!] })
+                ],
+                parser: 'svelte'
+            });
+        });
+
         const defaultSettings = {
             svelteSortOrder: 'options-scripts-markup-styles',
             svelteStrictMode: false,