resolveDebugConfiguration returns null to tell vscode to continue generating launch.json (#430)

* resolveDebugConfiguration returns null to tell vscode to continue generating launch.json

Signed-off-by: Jinbo Wang <[email protected]>

* Use truthy to check the value is empty or not

Author: testforstephen

src/configurationProvider.ts

@@ -135,9 +135,12 @@ export class JavaDebugConfigurationProvider implements vscode.DebugConfiguration
              * If no launch.json exists in the current workspace folder
              * delegate to provideDebugConfigurations api to generate the initial launch.json configurations
              */
-            if (this.isEmptyConfig(config) && folder !== undefined) {
-                return config;
+            if (this.isEmptyConfig(config) && folder) {
+                // Follow the feature request https://github.com/Microsoft/vscode/issues/54213#issuecomment-420965778,
+                // in order to generate launch.json, the resolveDebugConfiguration api must return null explicitly.
+                return null;
             }
+
             // If it's the single file case that no workspace folder is opened, generate debug config in memory
             if (this.isEmptyConfig(config) && !folder) {
                 config.type = "java";