Add gotodefinition support for stdlib

client/package.json

@@ -13,6 +13,7 @@
     "vscode": "^1.43.0"
   },
   "dependencies": {
+    "adm-zip": "^0.5.10",
     "vscode-languageclient": "^8.0.1"
   },
   "devDependencies": {

client/src/extension.ts

@@ -13,6 +13,7 @@ import initialiseState from './services/state'
 import * as handlers from './handlers'
 import { callResolversAndEmptyList } from './services/timers'
 import { registerFlixReleaseDocumentProvider } from './services/releaseVirtualDocument'
+import { registerFlixStdlibDocumentProvider } from './services/stdlibVirtualDocument'
 import { USER_MESSAGE } from './util/userMessages'
 import { StatusCode } from './util/statusCodes'
 
@@ -110,6 +111,7 @@ export async function activate(context: vscode.ExtensionContext, launchOptions:
   initialiseState(context)
 
   registerFlixReleaseDocumentProvider(context)
+  registerFlixStdlibDocumentProvider(context)
 
   // create output channels
   outputChannel = vscode.window.createOutputChannel('Flix Compiler')

client/src/handlers/handlers.ts

@@ -158,6 +158,11 @@ export function handleChangeEditor(editor: vscode.TextEditor | undefined) {
     return
   }
 
+  // Skip validation for virtual URIs (like stdlib files from JAR)
+  if (editor.document.uri.scheme !== 'file') {
+    return
+  }
+
   const included = vscode.languages.match({ pattern: FLIX_GLOB_PATTERN }, editor.document)
   if (!included) {
     vscode.window.showWarningMessage(USER_MESSAGE.FILE_NOT_PART_OF_PROJECT())

client/src/services/stdlibVirtualDocument.ts

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2025 Valentin Erokhin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as vscode from 'vscode'
+import AdmZip from 'adm-zip'
+import * as fs from 'fs'
+
+/**
+ * The scheme used to distinguish stdlib documents from jar files.
+ */
+const scheme = 'flixstdlib'
+
+/**
+ * Handle documents where the uri scheme is [[scheme]] (flixstdlib):
+ * - Extract the jar path and file path from the URI
+ * - Read the file content from inside the jar
+ * - Return the file content for display
+ */
+const flixStdlibDocumentProvider = new (class implements vscode.TextDocumentContentProvider {
+  provideTextDocumentContent(uri: vscode.Uri): string {
+    try {
+      const jarPath = decodeURIComponent(uri.authority)
+      const filePath = uri.path.startsWith('/') ? uri.path.substring(1) : uri.path
+
+      if (!fs.existsSync(jarPath)) {
+        return `// Error: Flix jar file not found at: ${jarPath}`
+      }
+
+      const zip = new AdmZip(jarPath)
+      let entry = zip.getEntry(filePath)
+      let searchedPaths = [filePath]
+
+      // If not found at root level, try common stdlib directories
+      if (!entry && !filePath.startsWith('src/')) {
+        const commonPaths = [
+          `src/library/${filePath}`,
+          `src/resources/${filePath}`,
+        ]
+
+        for (const path of commonPaths) {
+          entry = zip.getEntry(path)
+          searchedPaths.push(path)
+          if (entry) break
+        }
+      }
+
+      if (!entry) {
+        return `// Error: File '${filePath}' not found in jar: ${jarPath}\n// Searched paths: ${searchedPaths.join(', ')}`
+      }
+
+      return entry.getData().toString('utf8')
+    } catch (error) {
+      return `// Error reading stdlib file: ${error.message}`
+    }
+  }
+})()
+
+/**
+ * Register the stdlib document provider.
+ */
+export function registerFlixStdlibDocumentProvider({ subscriptions }: vscode.ExtensionContext) {
+  subscriptions.push(vscode.workspace.registerTextDocumentContentProvider(scheme, flixStdlibDocumentProvider))
+} 

server/src/handlers/handlers.ts

@@ -208,6 +208,14 @@ function makeGotoDefinitionResponseHandler(promiseResolver: (result?: socket.Fli
     if (status === StatusCode.Success) {
       if (targetUri?.startsWith('file://')) {
         return promiseResolver(result)
+      } else if (targetUri && isStdlibFile(targetUri)) {
+        const flixJarPath = engine.getFlixFilename()
+        const virtualUri = `flixstdlib://${encodeURIComponent(flixJarPath)}/${targetUri}`
+
+        return promiseResolver({
+          ...result,
+          targetUri: virtualUri
+        })
       } else {
         sendNotification(jobs.Request.internalMessage, USER_MESSAGE.FILE_NOT_AVAILABLE(targetUri!))
       }
@@ -216,6 +224,24 @@ function makeGotoDefinitionResponseHandler(promiseResolver: (result?: socket.Fli
   }
 }
 
+/**
+ * Determines if a target URI represents a stdlib file that should be loaded from the flix.jar
+ */
+function isStdlibFile(targetUri: string): boolean {
+  // Stdlib files are typically:
+  // 1. Flix source files (end with .flix)
+  // 2. Just filenames without directory paths (no '/' characters)
+  // 3. Not absolute paths or URLs
+  return (
+    targetUri.endsWith('.flix') &&
+    !targetUri.includes('/') &&
+    !targetUri.includes('\\') &&
+    !targetUri.startsWith('http') &&
+    !targetUri.includes(':') &&
+    targetUri.length > 0
+  )
+}
+
 /**
  * @function
  */