Add support for vm args config setting

lib/main.js

@@ -43,16 +43,23 @@ class JavaLanguageClient extends AutoLanguageClient {
       })
       .then(() => this.getOrCreateDataDir(projectPath))
       .then(dataDir => {
-        const args = [
+        const args = []
+        if (javaVersion >= 9) {
+          args.push(
+            '--add-modules=ALL-SYSTEM',
+      		  '--add-opens', 'java.base/java.util=ALL-UNNAMED',
+      		  '--add-opens', 'java.base/java.lang=ALL-UNNAMED'
+          )
+        }
+
+        const extraArgs = this.parseArgs(atom.config.get('ide-java.virtualMachine.extraArgs'))
+        args.push(...extraArgs)
+
+        args.push(
           '-jar', path.join(serverHome, serverLauncher),
           '-configuration', path.join(serverHome, `config_${config}`),
           '-data', dataDir
-        ]
-        if (javaVersion >= 9) {
-          args.push('--add-modules=ALL-SYSTEM');
-      		args.push('--add-opens', 'java.base/java.util=ALL-UNNAMED');
-      		args.push('--add-opens', 'java.base/java.lang=ALL-UNNAMED');
-        }
+        )
 
         this.logger.debug(`starting "${command} ${args.join(' ')}"`)
         const childProcess = cp.spawn(command, args, { cwd: serverHome })
@@ -253,6 +260,17 @@ class JavaLanguageClient extends AutoLanguageClient {
       })
     })
   }
+
+  parseArgs(argsLine) {
+  	if (!argsLine) return []
+
+    // Split the args into an array based on whitespace outside of double-quotes
+  	const args = argsLine.match(/(?:[^\s"]+|"[^"]*")+/g)
+  	if (args === null) return []
+
+    // Remove double quotes
+  	return args.map(arg => arg.replace(/(\\)?"/g, (a, b) => a ? b : '').replace(/(\\)"/g, '"'))
+  }
 }
 
 module.exports = new JavaLanguageClient()

package.json

@@ -18,9 +18,20 @@
       "default": "",
       "description": "Absolute path to Java 8 or later home folder used to launch the Java language server."
     },
-    "errors": {
+    "virtualMachine": {
       "order": 20,
       "type": "object",
+      "properties": {
+        "extraArgs": {
+          "type": "string",
+          "default": "-noverify -Xmx1G -XX:+UseG1GC -XX:+UseStringDeduplication",
+          "description": "Extra arguments passed to the Java VM when launching the Java Language Server. Eg. use `-noverify -Xmx1G  -XX:+UseG1GC -XX:+UseStringDeduplication` to bypass class verification, increase the heap size to 1GB and enable String deduplication with the G1 Garbage collector."
+        }
+      }
+    },
+    "errors": {
+      "order": 30,
+      "type": "object",
       "title": "Warnings and Errors",
       "properties": {
         "incompleteClasspathSeverity": {
@@ -33,7 +44,7 @@
             "error"
           ],
           "default": "warning",
-          "description": "Specifies the severity of the message when the classpath is incomplete for a Java file."
+          "description": "Severity of the message when the classpath is incomplete for a Java file."
         }
       }
     }