Show setup message when no targets returned from sync (#15)

When a sync completes and returns no targets, it's likely that the user
needs to make adjustments to their .bazelproject file.

This change adds guidance for the user to resolve issues and re-sync:
- When no targets are returned, error message shown immediately below
the root item, with access to .bazelproject file. This only supports one
line, so we can't include full details here.
- Detailed instructions will be surfaced at the top of the .bazelproject
file, and in the lower test results panel:


![image](https://github.com/uber/vscode-bazel-bsp/assets/92764374/38d3d462-a935-47eb-b6fa-0c988609e946)

![image](https://github.com/uber/vscode-bazel-bsp/assets/92764374/af770943-4193-4e0e-8cdd-abd85ddcb9a7)

Author: mnoah1

src/test-explorer/resolver.ts

@@ -159,6 +159,7 @@ export class TestResolver implements OnModuleInit, vscode.Disposable {
       parentTest,
       'Loading: waiting for build server connection'
     )
+    parentTest.error = undefined
     const conn = await this.buildServer.getConnection()
 
     updateDescription(parentTest, 'Loading: fetching available targets')
@@ -212,6 +213,25 @@ export class TestResolver implements OnModuleInit, vscode.Disposable {
       relevantParent.children.add(newTest)
     })
 
+    // If no test items were added, show the getting started message as a test message overlaid on the .bazelproject file.
+    // This provides an opportunity for the user to make adjustments and re-sync.
+    if (parentTest.children.size === 0) {
+      // Dummy test run that overlays the getting started message on the .bazelproject file.
+      const run = this.store.testController.createTestRun(
+        new vscode.TestRunRequest()
+      )
+      run.errored(parentTest, new vscode.TestMessage(gettingStartedMessage))
+      run.end()
+
+      // Link in the test explorer tree to set up the project.
+      const encodedFileUri = encodeURIComponent(JSON.stringify(parentTest.uri))
+      const syncFailMessage = new vscode.MarkdownString(
+        `No test targets found. [Setup your project](command:vscode.open?${encodedFileUri})`
+      )
+      syncFailMessage.isTrusted = true
+      parentTest.error = syncFailMessage
+    }
+
     // Replace all children with the newly returned test cases.
     this.condenseTestItems(parentTest)
     updateDescription(parentTest)
@@ -413,3 +433,19 @@ function combineCancelTokens(
   token2?.onCancellationRequested(() => combinedSource.cancel())
   return combinedSource.token
 }
+
+const gettingStartedMessage = new vscode.MarkdownString(
+  `To use the Test Explorer, please configure your project.
+
+  Getting started tips:
+  - Update this file with some paths that include test targets.
+    - Use the directories key to specify by directory
+    - Use the targets key to specify by Bazel target pattern
+  - Ensure that the bazel_binary field in this file matches the path to your Bazel binary.
+  - Re-sync at any time by clicking the $(extensions-refresh) refresh icon at the very top of the testing panel.
+
+  Think something else went wrong? Check the output [here](command:bazelbsp.showServerOutput).
+  `,
+  true
+)
+gettingStartedMessage.isTrusted = true

src/test-info/test-item-factory.ts

@@ -36,6 +36,7 @@ export class TestItemFactory {
       'Bazel Test Targets',
       uri
     )
+    newTest.range = new vscode.Range(0, 0, 0, 0)
     newTest.canResolveChildren = true
     this.store.testCaseMetadata.set(
       newTest,

src/test/suite/resolver.test.ts

@@ -344,6 +344,30 @@ suite('Test Resolver', () => {
       }
     })
 
+    test('no targets returned', async () => {
+      const root = testCaseStore.testController.createTestItem(
+        'root',
+        'Bazel Test Targets'
+      )
+      testCaseStore.testController.items.add(root)
+      testCaseStore.testCaseMetadata.set(
+        root,
+        new TestCaseInfo(root, undefined, TestItemType.Root)
+      )
+      assert.ok(testCaseStore.testController.resolveHandler)
+
+      // Simulate an empty result from requesting targets.
+      const emptyResult: bsp.WorkspaceBuildTargetsResult = {
+        targets: [],
+      }
+      const sendRequestStub = sandbox
+        .stub(sampleConn, 'sendRequest')
+        .resolves(emptyResult)
+      await testCaseStore.testController.resolveHandler(root)
+      const message = root.error as vscode.MarkdownString
+      assert.ok(message.value.includes('No test targets found'))
+    })
+
     test('source files within a target', async () => {
       const buildTarget = sampleBuildTargetsResult.targets[0]
       const sendRequestStub = sandbox