Add support for VS Code Quick Fixes

Closes GH-17.

Reviewed-by: Titus Wormer <[email protected]>

lib/index.js

@@ -17,6 +17,8 @@ import {engine} from 'unified-engine'
 import {VFile} from 'vfile'
 import {
   createConnection,
+  CodeAction,
+  CodeActionKind,
   Diagnostic,
   DiagnosticSeverity,
   Position,
@@ -102,6 +104,12 @@ function vfileMessageToDiagnostic(message) {
     diagnostic.codeDescription = {href: message.url}
   }
 
+  if (message.expected) {
+    diagnostic.data = {
+      expected: message.expected
+    }
+  }
+
   return diagnostic
 }
 
@@ -199,7 +207,11 @@ export function configureUnifiedLanguageServer(
   connection.onInitialize(() => ({
     capabilities: {
       textDocumentSync: TextDocumentSyncKind.Full,
-      documentFormattingProvider: true
+      documentFormattingProvider: true,
+      codeActionProvider: {
+        codeActionKinds: [CodeActionKind.QuickFix],
+        resolveProvider: true
+      }
     }
   }))
 
@@ -238,6 +250,59 @@ export function configureUnifiedLanguageServer(
   connection.onDidChangeWatchedFiles(() => {
     checkDocuments(...documents.all())
   })
+
+  connection.onCodeAction((event) => {
+    /** @type {CodeAction[]} */
+    const codeActions = []
+
+    const document = documents.get(event.textDocument.uri)
+    if (!document) {
+      return
+    }
+
+    const text = document.getText()
+
+    for (const diagnostic of event.context.diagnostics) {
+      const {data} = diagnostic
+      if (typeof data !== 'object' || !data) {
+        continue
+      }
+
+      const {expected} = /** @type {{expected?: string[]}} */ (data)
+
+      if (!Array.isArray(expected)) {
+        continue
+      }
+
+      const {end, start} = diagnostic.range
+      const actual = text.slice(
+        document.offsetAt(start),
+        document.offsetAt(end)
+      )
+
+      for (const replacement of expected) {
+        codeActions.push(
+          CodeAction.create(
+            replacement
+              ? start.line === end.line && start.character === end.character
+                ? 'Insert `' + replacement + '`'
+                : 'Replace `' + actual + '` with `' + replacement + '`'
+              : 'Remove `' + actual + '`',
+            {
+              changes: {
+                [document.uri]: [
+                  TextEdit.replace(diagnostic.range, replacement)
+                ]
+              }
+            },
+            CodeActionKind.QuickFix
+          )
+        )
+      }
+    }
+
+    return codeActions
+  })
 }
 
 /**

readme.md

@@ -154,6 +154,11 @@ options.
 Language servers created using this package implement the following language
 server features:
 
+*   `textDocument/codeAction`
+    — The language server implements code actions based on the `expected` field
+    on reported messages.
+    A code action can either insert, replace, or delete text based on the range
+    of the message and the expected value.
 *   `textDocument/didChange`
     — when a document is changed by the client, the language server processes it
     using a unified pipeline.

test/index.js

@@ -4,6 +4,7 @@ import {spy, stub} from 'sinon'
 import test from 'tape'
 import * as exports from 'unified-language-server'
 import {
+  CodeActionKind,
   DiagnosticSeverity,
   Position,
   Range,
@@ -34,6 +35,7 @@ function createMockConnection() {
     onInitialize: spy(),
     onDidChangeConfiguration: spy(),
     onDidChangeWatchedFiles: spy(),
+    onCodeAction: spy(),
     onDocumentFormatting: spy(),
     sendDiagnostics: stub()
   }
@@ -83,7 +85,11 @@ test('onInitialize', (t) => {
   t.deepEquals(result, {
     capabilities: {
       textDocumentSync: TextDocumentSyncKind.Full,
-      documentFormattingProvider: true
+      documentFormattingProvider: true,
+      codeActionProvider: {
+        codeActionKinds: [CodeActionKind.QuickFix],
+        resolveProvider: true
+      }
     }
   })
 
@@ -354,6 +360,26 @@ test('onDidChangeContent has error', async (t) => {
   t.end()
 })
 
+test('onDidChangeContent expected', async (t) => {
+  const uri = String(pathToFileURL('test.md'))
+  const diagnostics = await getDiagnostic(uri, 'expected')
+
+  t.deepEquals(diagnostics, {
+    uri,
+    version: 0,
+    diagnostics: [
+      {
+        data: {expected: ['suggestion']},
+        range: {start: {line: 0, character: 0}, end: {line: 0, character: 0}},
+        message: 'expected',
+        severity: DiagnosticSeverity.Warning
+      }
+    ]
+  })
+
+  t.end()
+})
+
 test('onDidClose', async (t) => {
   const connection = createMockConnection()
   const documents = new TextDocuments(TextDocument)
@@ -454,6 +480,117 @@ test('onDidChangeWatchedFiles', async (t) => {
   t.end()
 })
 
+test('onCodeAction not found', async (t) => {
+  const connection = createMockConnection()
+  const documents = new TextDocuments(TextDocument)
+
+  configureUnifiedLanguageServer(connection, documents, {
+    plugins: ['./test/test-plugin.js']
+  })
+
+  const onCodeAction = /** @type import('sinon').SinonSpy */ (
+    connection.onCodeAction
+  )
+  const codeActions = onCodeAction.firstCall.firstArg({
+    textDocument: {uri: 'file:///non-existent.txt'}
+  })
+
+  t.equals(codeActions, undefined)
+})
+
+test('onCodeAction diagnostics', async (t) => {
+  const connection = createMockConnection()
+  const documents = new TextDocuments(TextDocument)
+  const uri = String(pathToFileURL('test.txt'))
+
+  Object.defineProperty(documents, 'get', {
+    value: () => TextDocument.create(uri, 'text', 0, 'invalid')
+  })
+
+  configureUnifiedLanguageServer(connection, documents, {
+    plugins: ['./test/test-plugin.js']
+  })
+
+  const onCodeAction = /** @type import('sinon').SinonSpy */ (
+    connection.onCodeAction
+  )
+  const codeActions = onCodeAction.firstCall.firstArg({
+    textDocument: {uri},
+    context: {
+      diagnostics: [
+        {},
+        {data: null},
+        {
+          data: {expected: ['text to insert']},
+          range: {start: {line: 0, character: 0}, end: {line: 0, character: 0}}
+        },
+        {
+          data: {expected: ['replacement text']},
+          range: {start: {line: 0, character: 0}, end: {line: 0, character: 7}}
+        },
+        {
+          data: {expected: ['']},
+          range: {start: {line: 0, character: 0}, end: {line: 0, character: 7}}
+        }
+      ]
+    }
+  })
+
+  t.deepEquals(codeActions, [
+    {
+      title: 'Insert `text to insert`',
+      kind: CodeActionKind.QuickFix,
+      edit: {
+        changes: {
+          [uri]: [
+            {
+              newText: 'text to insert',
+              range: {
+                start: {line: 0, character: 0},
+                end: {line: 0, character: 0}
+              }
+            }
+          ]
+        }
+      }
+    },
+    {
+      title: 'Replace `invalid` with `replacement text`',
+      kind: CodeActionKind.QuickFix,
+      edit: {
+        changes: {
+          [uri]: [
+            {
+              newText: 'replacement text',
+              range: {
+                start: {line: 0, character: 0},
+                end: {line: 0, character: 7}
+              }
+            }
+          ]
+        }
+      }
+    },
+    {
+      title: 'Remove `invalid`',
+      kind: CodeActionKind.QuickFix,
+      edit: {
+        changes: {
+          [uri]: [
+            {
+              newText: '',
+              range: {
+                start: {line: 0, character: 0},
+                end: {line: 0, character: 7}
+              }
+            }
+          ]
+        }
+      }
+    }
+  ])
+})
+
 test('exports', (t) => {
   t.equal(exports.createUnifiedLanguageServer, createUnifiedLanguageServer)
 

test/test-plugin.js

@@ -56,6 +56,11 @@ export default function unifiedTestPlugin() {
       message.url = 'https://example.com'
     }
 
+    if (value.includes('expected')) {
+      const message = file.message('expected')
+      message.expected = ['suggestion']
+    }
+
     if (value.includes('has error')) {
       throw new Error('Test error')
     }