Fixed workspace variable resolver.

Fall back to the current sketch, if `currentWidget` points to a file
outside of the workspace.

Closes: arduino/arduino-ide#46

Signed-off-by: Akos Kitta <kittaakos@typefox.io>

arduino-ide-extension/src/browser/theia/workspace/workspace-variable-contribution.ts

@@ -0,0 +1,29 @@
+import { inject, injectable, postConstruct } from 'inversify';
+import URI from '@theia/core/lib/common/uri';
+import { WorkspaceVariableContribution as TheiaWorkspaceVariableContribution } from '@theia/workspace/lib/browser/workspace-variable-contribution';
+import { Sketch } from '../../../common/protocol';
+import { SketchesServiceClientImpl } from '../../../common/protocol/sketches-service-client-impl';
+
+@injectable()
+export class WorkspaceVariableContribution extends TheiaWorkspaceVariableContribution {
+
+    @inject(SketchesServiceClientImpl)
+    protected readonly sketchesServiceClient: SketchesServiceClientImpl;
+
+    protected currentSketch?: Sketch;
+
+    @postConstruct()
+    protected init(): void {
+        this.sketchesServiceClient.currentSketch().then().then(sketch => this.currentSketch = sketch);
+    }
+
+    getResourceUri(): URI | undefined {
+        const resourceUri = super.getResourceUri();
+        // https://github.com/arduino/arduino-ide/issues/46
+        // `currentWidget` can be an editor representing a file outside of the workspace. The current sketch should be a fallback.
+        if (!resourceUri && this.currentSketch?.uri) {
+            return new URI(this.currentSketch.uri);
+        }
+        return resourceUri;
+    }
+}