Prompt API: Normalize empty message sequences in append()

Align empty message sequence handling with prompt(); refine tests.

Bug: 490181853
Change-Id: Iaa4d228029eb37edb327ebdda9831bd0d69a35ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7703522
Reviewed-by: Jingyun Liu <jingyun@google.com>
Commit-Queue: Jingyun Liu <jingyun@google.com>
Auto-Submit: Mike Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1606451}

Author: Mike Wasserman

ai/language-model/language-model-append.tentative.https.window.js

@@ -23,17 +23,6 @@ promise_test(async () => {
   assert_equals(session.contextUsage, promptUsage);
 }, 'Check contextUsage increases from a simple LanguageModel.append() call');
 
-promise_test(async (t) => {
-  await ensureLanguageModel();
-  const session = await createLanguageModel();
-  assert_equals(session.contextUsage, 0);
-  await session.append([]);
-  assert_equals(session.contextUsage, 0);
-  // Invalid input should be stringified.
-  await session.append({});
-  assert_greater_than(session.contextUsage, 0);
-}, 'Check empty Object input for LanguageModel.append()');
-
 promise_test(async t => {
   await ensureLanguageModel();
   const session = await createLanguageModel();
@@ -63,3 +52,17 @@ promise_test(async t => {
       t, TypeError, session.append([{role: 'system', content: 'bar'}]));
   await result3;
 }, 'append() should reject system role messages after other messages');
+
+promise_test(async (t) => {
+  await ensureLanguageModel();
+  const model = await createLanguageModel();
+
+  // null, undefined, and objects are coerced to strings.
+  await model.append(null);
+  await model.append(undefined);
+  await model.append({});
+  await model.append('');
+  await model.append([]);
+  await model.append([{ role: 'user', content: [] }]);
+  await model.append([{role: 'user', content: [{type: 'text', value: ''}]}]);
+}, 'LanguageModel.append() allows empty and coerced inputs');

ai/language-model/language-model-prompt-empty-input.tentative.https.window.js

@@ -16,10 +16,7 @@ promise_test(async t => {
     session.promptStreaming(kTestPrompt);
   // Run GC.
   gc();
-  assert_equals(
-    Object.prototype.toString.call(streamingResponse),
-    "[object ReadableStream]"
-  );
+  assert_true(streamingResponse instanceof ReadableStream);
   let result = "";
   for await (const value of streamingResponse) {
     result += value;

ai/language-model/language-model-prompt-streaming-gc.tentative.https.window.js

@@ -8,26 +8,23 @@
 
 promise_test(async t => {
   await ensureLanguageModel();
-
-  // Start a new session.
   const session = await createLanguageModel();
-  // Test the streaming prompt API.
-  const streamingResponse =
-    session.promptStreaming(kTestPrompt);
-  assert_equals(
-    Object.prototype.toString.call(streamingResponse),
-    "[object ReadableStream]"
-  );
-  const reader = streamingResponse.getReader();
-  let result = "";
-  while (true) {
-    const { value, done } = await reader.read();
-    if (done) {
-      break;
-    }
-    if (value) {
-      result += value;
-    }
-  }
-  assert_greater_than(result.length, 0, "The result should not be empty.");
+  const streamingResponse = session.promptStreaming(kTestPrompt);
+  assert_true(streamingResponse instanceof ReadableStream);
+  const result = (await Array.fromAsync(streamingResponse)).join('');
+  assert_greater_than(result.length, 0, 'The result should not be empty.');
 });
+
+promise_test(async (t) => {
+  await ensureLanguageModel();
+  const model = await createLanguageModel();
+
+  // null, undefined, and objects are coerced to strings.
+  for await (const _ of model.promptStreaming(null)) { }
+  for await (const _ of model.promptStreaming(undefined)) { }
+  for await (const _ of model.promptStreaming({})) { }
+  for await (const _ of model.promptStreaming('')) { }
+  for await (const _ of model.promptStreaming([])) { }
+  for await (const _ of model.promptStreaming([{ role: 'user', content: [] }])) { }
+  for await (const _ of model.promptStreaming([{ role: 'user', content: [{ type: 'text', value: '' }] }])) { }
+}, 'LanguageModel.promptStreaming() allows empty and coerced inputs');

ai/language-model/language-model-prompt-streaming.tentative.https.window.js

@@ -33,6 +33,24 @@ promise_test(async (t) => {
   assert_regexp_match(await session.prompt({}), /\[object Object\]/);
 }, 'Check empty Object input');
 
+promise_test(async (t) => {
+  await ensureLanguageModel();
+  const model = await createLanguageModel();
+
+  // null, undefined, and objects are coerced to strings.
+  assert_regexp_match(await model.prompt(null), /null/);
+  assert_regexp_match(await model.prompt(undefined), /undefined/);
+  assert_equals(typeof await model.prompt({}), 'string');
+  assert_equals(typeof await model.prompt(''), 'string');
+  assert_equals(typeof await model.prompt([]), 'string');
+  assert_equals(
+      typeof await model.prompt([{role: 'user', content: []}]), 'string');
+  assert_equals(
+      typeof await model.prompt(
+          [{role: 'user', content: [{type: 'text', value: ''}]}]),
+      'string');
+}, 'LanguageModel.prompt() allows empty and coerced inputs');
+
 promise_test(async (t) => {
   await ensureLanguageModel();
   const session = await createLanguageModel();