Enable javac-based compilation

.github/workflows/release.yml

@@ -81,7 +81,7 @@ jobs:
       - name: Set Up Java
         uses: actions/setup-java@v4
         with:
-          java-version: '17'
+          java-version: '23'
           distribution: 'adopt'
       - name: Build JDT-LS
         if: "${{ inputs.JDT_LS_VERSION == '' }}"

README.md

@@ -254,6 +254,10 @@ The following settings are supported:
   - Call Hierarchy
   - Workspace Symbols
 
+New in 1.36.0
+* `java.jdt.ls.javac.enabled`: [Experimental] Specify whether to enable Javac-based compilation in the language server. Requires running this extension with Java 23. Defaults to `false`.
+* `java.completion.engine`: [Experimental] Select code completion engine. Defaults to `ecj`.
+
 Semantic Highlighting
 ===============
 [Semantic Highlighting](https://github.com/redhat-developer/vscode-java/wiki/Semantic-Highlighting) fixes numerous syntax highlighting issues with the default Java Textmate grammar. However, you might experience a few minor issues, particularly a delay when it kicks in, as it needs to be computed by the Java Language server, when opening a new file or when typing. Semantic highlighting can be disabled for all languages using the `editor.semanticHighlighting.enabled` setting, or for Java only using [language-specific editor settings](https://code.visualstudio.com/docs/getstarted/settings#_languagespecific-editor-settings).

USAGE_DATA.md

@@ -19,10 +19,10 @@ vscode-java has opt-in telemetry collection, provided by [vscode-redhat-telemetr
  * Errors relating to running the language server, such as the message & stacktrace
  * Whether there is a mismatch between the project's requested source level, and the JDK used for the project (eg. true)
  * Information about the following settings. In the case of settings that store a well defined value (eg. path/url/string), we simply collect whether the setting has been set.
-   * `java.settings.url`, `java.format.settings.url`, `java.quickfix.showAt`, `java.symbols.includeSourceMethodDeclarations`, `java.completion.collapseCompletionItems`, `java.completion.guessMethodArguments`, `java.completion.postfix.enabled`, `java.cleanup.actionsOnSave`, `java.sharedIndexes.enabled`, `java.inlayHints.parameterNames.enabled`, `java.server.launchMode`, `java.autobuild.enabled`
+   * `java.settings.url`, `java.format.settings.url`, `java.quickfix.showAt`, `java.symbols.includeSourceMethodDeclarations`, `java.completion.collapseCompletionItems`, `java.completion.guessMethodArguments`, `java.completion.postfix.enabled`, `java.cleanup.actionsOnSave`, `java.sharedIndexes.enabled`, `java.inlayHints.parameterNames.enabled`, `java.server.launchMode`, `java.autobuild.enabled`, `java.jdt.ls.javac.enabled`
  * The extension name and the choice made when a recommendation to install a 3rd party extension is proposed
  * The name of Java commands being manually executed, and any resulting errors
- * The number of results (eg. 20), whether an error occured (eg. false), and duration (in milliseconds) when code assist is activated
+ * The number of results (eg. 20), whether an error occured (eg. false), engine type (eg. 'ecj', 'dom') and duration (in milliseconds) when code assist is activated
  * Whether the language server ran out of memory and the maximum allocated memory at which that occured (eg. 200m)
 
 ## What's included in the general telemetry data

package.json

@@ -409,6 +409,17 @@
             "scope": "window",
             "order": 90
           },
+          "java.jdt.ls.javac.enabled": {
+            "type": "string",
+            "enum": [
+              "on",
+              "off"
+            ],
+            "default": "off",
+            "markdownDescription": "[Experimental] Specify whether to enable Javac-based compilation in the language server. Requires running this extension with Java 23",
+            "scope": "window",
+            "order": 95
+          },
           "java.trace.server": {
             "type": "string",
             "enum": [
@@ -1009,6 +1020,21 @@
             "scope": "window",
             "order": 10
           },
+          "java.completion.engine": {
+            "type": "string",
+            "default": "ecj",
+            "description": "[Experimental] Select code completion engine",
+            "scope": "window",
+            "enum": [
+              "ecj",
+              "dom"
+            ],
+            "markdownEnumDescriptions": [
+              "Use ECJ-based code completion engine (default)",
+              "Use (highly experimental) JDT DOM-based code completion engine (requires `java.jdt.ls.javac.enabled` to be `on`)"
+            ],
+            "order": 1000
+          },
           "java.completion.postfix.enabled": {
             "type": "boolean",
             "default": true,
@@ -1939,4 +1965,4 @@
   },
   "segmentWriteKey": "Y7Y5Xk8dKEhVZHTmAkFZkqgdN4d7c4lt",
   "segmentWriteKeyDebug": "BflPll7uuKOCm3y0g7JpfXLVBVFBivDE"
-}
+}

src/extension.ts

@@ -1203,6 +1203,7 @@ export function registerCodeCompletionTelemetryListener() {
 				resultLength: traceEvent.resultLength || 0,
 				error: !!traceEvent.error,
 				fromSyntaxServer: !!traceEvent.fromSyntaxServer,
+				engine: getJavaConfiguration().get('completion.engine'),
 			};
 			return Telemetry.sendTelemetry(Telemetry.COMPLETION_EVENT, props);
 		}

src/javaServerStarter.ts

@@ -104,7 +104,40 @@ function prepareParams(requirements: RequirementsData, workspacePath, context: E
 				// See https://github.com/redhat-developer/vscode-java/issues/2264
 				// It requires the internal API sun.nio.fs.WindowsFileAttributes.isDirectoryLink() to check if a Windows directory is symlink.
 				'--add-opens',
-				'java.base/sun.nio.fs=ALL-UNNAMED');
+				'java.base/sun.nio.fs=ALL-UNNAMED'
+				);
+
+	const javacEnabled = 'on' === getJavaConfiguration().get('jdt.ls.javac.enabled');
+	if (javacEnabled) {
+		// Javac flags
+		params.push(
+		'--add-opens',
+		'jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED',
+		'--add-opens',
+		'jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED',
+		'--add-opens',
+		'jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED',
+		'--add-opens',
+		'jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED',
+		'--add-opens',
+		'jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED',
+		'--add-opens',
+		'jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED',
+		'--add-opens',
+		'jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED',
+		'--add-opens',
+		'jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED',
+		'--add-opens',
+		'jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.taglets.snippet=ALL-UNNAMED --add-opens jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.taglets=ALL-UNNAMED',
+		'-DICompilationUnitResolver=org.eclipse.jdt.core.dom.JavacCompilationUnitResolver',
+		'-DCompilationUnit.DOM_BASED_OPERATIONS=true',
+		'-DAbstractImageBuilder.compilerFactory=org.eclipse.jdt.internal.javac.JavacCompilerFactory'
+		);
+
+		if('dom' === getJavaConfiguration().get('completion.engine')){
+			params.push('-DCompilationUnit.codeComplete.DOM_BASED_OPERATIONS=true');
+		};
+	}
 
 	params.push('-Declipse.application=org.eclipse.jdt.ls.core.id1',
 				'-Dosgi.bundles.defaultStartLevel=4',

src/requirements.ts

@@ -9,8 +9,8 @@ import { Commands } from './commands';
 import { logger } from './log';
 import { checkJavaPreferences } from './settings';
 import { listJdks, sortJdksBySource, sortJdksByVersion } from './jdkUtils';
+import { getJavaConfiguration } from './utils';
 
-const REQUIRED_JDK_VERSION = 17;
 /* eslint-disable @typescript-eslint/naming-convention */
 export interface RequirementsData {
     tooling_jre: string;
@@ -41,6 +41,7 @@ export async function resolveRequirements(context: ExtensionContext): Promise<Re
         const preferenceName = javaPreferences.preference;
         let javaHome = javaPreferences.javaHome;
         let javaVersion: number = 0;
+        const REQUIRED_JDK_VERSION = ('on' === getJavaConfiguration().get('jdt.ls.javac.enabled'))?23:17;
         if (javaHome) {
             const source = `${preferenceName} variable defined in ${env.appName} settings`;
             javaHome = expandHomeDir(javaHome);

src/settings.ts

@@ -137,7 +137,9 @@ function hasJavaConfigChanged(oldConfig: WorkspaceConfiguration, newConfig: Work
 		|| hasConfigKeyChanged('server.launchMode', oldConfig, newConfig)
 		|| hasConfigKeyChanged('sharedIndexes.location', oldConfig, newConfig)
 		|| hasConfigKeyChanged('transport', oldConfig, newConfig)
-		|| hasConfigKeyChanged('diagnostic.filter', oldConfig, newConfig);
+		|| hasConfigKeyChanged('diagnostic.filter', oldConfig, newConfig)
+		|| hasConfigKeyChanged('jdt.ls.javac.enabled', oldConfig, newConfig)
+		|| hasConfigKeyChanged('completion.engine', oldConfig, newConfig);
 }
 
 function hasConfigKeyChanged(key, oldConfig, newConfig) {

src/utils.ts

@@ -245,6 +245,19 @@ export async function getJavaConfig(javaHome: string) {
 			break;
 	}
 
+	const javacSupport = javaConfig.jdt.ls.javac.enabled;
+	switch (javacSupport) {
+		case "on":
+			javaConfig.jdt.ls.javac.enabled = true;
+			break;
+		case "off":
+			javaConfig.jdt.ls.javac.enabled = false;
+			break;
+		default:
+			javaConfig.jdt.ls.javac.enabled = false;
+			break;
+	}
+
 	if (javaConfig.completion.matchCase === "auto") {
 		javaConfig.completion.matchCase = "firstLetter";
 	}