Include samples in completions when the document is empty (#2009)

Fixing the behavior that regressed in #1947 when I was attempting to
limit samples to empty documents only.

Author: minestarks

vscode/src/completion.ts

@@ -89,7 +89,17 @@ class QSharpCompletionItemProvider implements vscode.CompletionItemProvider {
       return item;
     });
 
-    // Include the samples list for empty documents
-    return document.lineCount > 0 ? results : results.concat(this.samples);
+    // Include the samples in contexts that are syntactically appropriate.
+    // The presence of the "operation" keyword in the completion list is a
+    // hint that the cursor is at a point we can insert the sample code.
+
+    const shouldIncludeSamples =
+      results.findIndex(
+        (i) =>
+          i.kind === vscode.CompletionItemKind.Keyword &&
+          i.label === "operation",
+      ) !== -1;
+
+    return !shouldIncludeSamples ? results : results.concat(this.samples);
   }
 }

vscode/test/suites/language-service/language-service.test.ts

@@ -79,6 +79,24 @@ suite("Q# Language Service Tests", function suite() {
       actualCompletionList.items.map((i) => i.label),
       "operation",
     );
+
+    assert.include(
+      actualCompletionList.items.map((i) => i.label),
+      "Shor sample",
+    );
+  });
+
+  test("Completions - don't include samples when syntactically inappropriate", async () => {
+    const actualCompletionList = (await vscode.commands.executeCommand(
+      "vscode.executeCompletionItemProvider",
+      testQs,
+      new vscode.Position(12, 0), // put the cursor after the namespace declaration
+    )) as vscode.CompletionList;
+
+    assert.notInclude(
+      actualCompletionList.items.map((i) => i.label),
+      "Shor sample",
+    );
   });
 
   test("Definition", async () => {