Introduce EvalJs, a replacement for ExecuteScript and friends.

EvalJs has the following improvements over ExecuteScript:
 - One function that works for every return type
   (no AndExtractBool etc variants) and every fancy
   option (isolated worlds, user gestures).
 - No out-params; no out-param variables.
 - |script| doesn't need to call domAutomationController explicitly
   to return a value. Instead, it has eval() semantics -- the statement
   completion value becomes the result.
 - The result of EvalJs can be used directly in EXPECT_EQ; e.g.::
   EXPECT_EQ("about:blank", EvalJs(contents, "window.location.href"));
 - JS exceptions are reliably captured and will appear as C++ assertion
   failures.
 - JS stack traces arising from exceptions are annotated with the
   corresponding source code; this also appears in C++ assertion failures.
 - When a script doesn't produce a result, tests are much less likely
   to hang.
 - Doesn't get confused by crosstalk with other callers
   of domAutomationController.send().
 - Lists, dicts, null values, etc. can be returned as base::Values.

Limitations/warts:
 - The reliance on eval() currently means that a CSP script-src
   directive can interfere with the script runner. There is
   a workaround (use an isolated world), but this limitation
   currently prevents ExecJs from being a drop-in replacement
   for ExecuteScript. Fixing that will be a follow-on.

Change-Id: I260595094f71e7734d29a78e9ffd90b409d74f37
Reviewed-on: https://chromium-review.googlesource.com/1125121
Commit-Queue: Nick Carter <nick@chromium.org>
Reviewed-by: Ben Greenstein <bengr@chromium.org>
Reviewed-by: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580702}

chrome/browser/dom_distiller/dom_distiller_viewer_source_browsertest.cc

@@ -376,12 +376,11 @@ IN_PROC_BROWSER_TEST_F(DomDistillerViewerSourceBrowserTest,
   // Wait for the page load to complete (this will be a distiller error page).
   content::WaitForLoadStop(contents);
 
-  bool result;
   // Execute in isolated world; where all distiller scripts are run.
-  EXPECT_TRUE(content::ExecuteScriptInIsolatedWorldAndExtractBool(
-      contents, ISOLATED_WORLD_ID_CHROME_INTERNAL, kTestDistillerObject,
-      &result));
-  EXPECT_TRUE(result);
+  EXPECT_EQ(true, content::EvalJsWithManualReply(
+                      contents, kTestDistillerObject,
+                      content::EXECUTE_SCRIPT_DEFAULT_OPTIONS,
+                      ISOLATED_WORLD_ID_CHROME_INTERNAL));
 }
 
 IN_PROC_BROWSER_TEST_F(DomDistillerViewerSourceBrowserTest,

content/browser/session_history_browsertest.cc

@@ -487,23 +487,15 @@ IN_PROC_BROWSER_TEST_F(SessionHistoryScrollAnchorTest,
 
 // http://code.google.com/p/chromium/issues/detail?id=56267
 IN_PROC_BROWSER_TEST_F(SessionHistoryTest, HistoryLength) {
-  int length;
-  ASSERT_TRUE(ExecuteScriptAndExtractInt(
-      shell(), "domAutomationController.send(history.length)", &length));
-  EXPECT_EQ(1, length);
-
+  EXPECT_EQ(1, EvalJs(shell(), "history.length"));
   NavigateToURL(shell(), GetURL("title1.html"));
 
-  ASSERT_TRUE(ExecuteScriptAndExtractInt(
-      shell(), "domAutomationController.send(history.length)", &length));
-  EXPECT_EQ(2, length);
+  EXPECT_EQ(2, EvalJs(shell(), "history.length"));
 
   // Now test that history.length is updated when the navigation is committed.
   NavigateToURL(shell(), GetURL("record_length.html"));
 
-  ASSERT_TRUE(ExecuteScriptAndExtractInt(
-      shell(), "domAutomationController.send(history.length)", &length));
-  EXPECT_EQ(3, length);
+  EXPECT_EQ(3, EvalJs(shell(), "history.length"));
 
   GoBack();
   GoBack();
@@ -511,9 +503,7 @@ IN_PROC_BROWSER_TEST_F(SessionHistoryTest, HistoryLength) {
   // Ensure history.length is properly truncated.
   NavigateToURL(shell(), GetURL("title2.html"));
 
-  ASSERT_TRUE(ExecuteScriptAndExtractInt(
-      shell(), "domAutomationController.send(history.length)", &length));
-  EXPECT_EQ(2, length);
+  EXPECT_EQ(2, EvalJs(shell(), "history.length"));
 }
 
 // Test that verifies that a cross-process transfer doesn't lose session
@@ -537,8 +527,7 @@ IN_PROC_BROWSER_TEST_F(SessionHistoryTest, GoBackToCrossSitePostWithRedirect) {
 
   // Submit the form.
   TestNavigationObserver form_post_observer(shell()->web_contents(), 1);
-  EXPECT_TRUE(
-      ExecuteScript(shell(), "document.getElementById('text-form').submit();"));
+  EXPECT_TRUE(ExecJs(shell(), "document.getElementById('text-form').submit()"));
   form_post_observer.Wait();
 
   // Verify that we arrived at the expected, redirected location.
@@ -547,13 +536,9 @@ IN_PROC_BROWSER_TEST_F(SessionHistoryTest, GoBackToCrossSitePostWithRedirect) {
 
   // Verify that POST body got preserved by 307 redirect.  This expectation
   // comes from: https://tools.ietf.org/html/rfc7231#section-6.4.7
-  std::string body;
-  EXPECT_TRUE(ExecuteScriptAndExtractString(
-      shell(),
-      "window.domAutomationController.send("
-      "document.getElementsByTagName('pre')[0].innerText);",
-      &body));
-  EXPECT_EQ("text=value\n", body);
+  EXPECT_EQ(
+      "text=value\n",
+      EvalJs(shell(), "document.getElementsByTagName('pre')[0].innerText"));
 
   // Navigate to a page from yet another site.
   EXPECT_TRUE(NavigateToURL(shell(), page_to_go_back_from));
@@ -568,13 +553,9 @@ IN_PROC_BROWSER_TEST_F(SessionHistoryTest, GoBackToCrossSitePostWithRedirect) {
             shell()->web_contents()->GetLastCommittedURL());
 
   // Again verify that POST body got preserved by 307 redirect.
-  std::string body_after_back_navigation;
-  EXPECT_TRUE(ExecuteScriptAndExtractString(
-      shell(),
-      "window.domAutomationController.send("
-      "document.getElementsByTagName('pre')[0].innerText);",
-      &body_after_back_navigation));
-  EXPECT_EQ("text=value\n", body_after_back_navigation);
+  EXPECT_EQ(
+      "text=value\n",
+      EvalJs(shell(), "document.getElementsByTagName('pre')[0].innerText"));
 }
 
 }  // namespace content

content/browser/web_contents/web_contents_impl_browsertest.cc

@@ -551,8 +551,7 @@ IN_PROC_BROWSER_TEST_F(WebContentsImplBrowserTest,
 
   NavigateToURL(shell(), kWebUIUrl);
 
-  bool js_executed = content::ExecuteScript(shell(), kJSCodeForAppendingFrame);
-  EXPECT_TRUE(js_executed);
+  EXPECT_TRUE(content::ExecuteScript(shell(), kJSCodeForAppendingFrame));
 }
 
 // Observer class to track the creation of RenderFrameHost objects. It is used

content/test/browser_test_utils_browsertest.cc

@@ -10,6 +10,7 @@
 #include "content/shell/browser/shell.h"
 #include "net/dns/mock_host_resolver.h"
 #include "net/test/embedded_test_server/embedded_test_server.h"
+#include "testing/gmock/include/gmock/gmock.h"
 
 namespace content {
 
@@ -79,4 +80,99 @@ IN_PROC_BROWSER_TEST_F(CrossSiteRedirectorBrowserTest,
   EXPECT_EQ(observer.redirect_url(), observer.navigation_url());
 }
 
+using EvalJsBrowserTest = ContentBrowserTest;
+
+IN_PROC_BROWSER_TEST_F(EvalJsBrowserTest, EvalJsErrors) {
+  ASSERT_TRUE(embedded_test_server()->Start());
+  NavigateToURL(shell(), embedded_test_server()->GetURL("/title2.html"));
+
+  {
+    // Test syntax errors.
+    auto result = EvalJs(shell(), "}}");
+    EXPECT_FALSE(true == result);
+    EXPECT_FALSE(false == result);  // EXPECT_FALSE(EvalJs()) shouldn't compile.
+    EXPECT_FALSE(0 == result);
+    EXPECT_FALSE(1 == result);
+    EXPECT_FALSE("}}" == result);  // EXPECT_EQ should fail
+    EXPECT_FALSE("}}" != result);  // As should EXPECT_NE
+    EXPECT_FALSE(nullptr == result);
+
+    std::string expected_error = R"(a JavaScript error:
+SyntaxError: Unexpected token }
+    at eval (<anonymous>)
+    at Promise.resolve.then.script (EvalJs-runner.js:2:34)
+)";
+    EXPECT_FALSE(expected_error == result);
+    EXPECT_EQ(expected_error, result.error);
+  }
+
+  {
+    // Test throwing exceptions.
+    auto result = EvalJs(shell(), "55; throw new Error('whoops');");
+    EXPECT_FALSE(55 == result);
+    EXPECT_FALSE(1 == result);
+    EXPECT_FALSE("whoops" == result);
+
+    std::string expected_error = R"(a JavaScript error:
+Error: whoops
+    at eval (__const_std::string&_script__:1:11):
+        55; throw new Error('whoops');
+                  ^^^^^
+    at eval (<anonymous>)
+    at Promise.resolve.then.script (EvalJs-runner.js:2:34)
+)";
+    EXPECT_FALSE(expected_error == result);
+    EXPECT_EQ(expected_error, result.error);
+  }
+
+  {
+    // Test reference errors in a multi-line script.
+    auto result = EvalJs(shell(), R"(
+    22;
+    var x = 200 + 300;
+    var y = z + x;
+    'sweet';)");
+    EXPECT_FALSE(22 == result);
+    EXPECT_FALSE("sweet" == result);
+
+    std::string expected_error = R"(a JavaScript error:
+ReferenceError: z is not defined
+    at eval (__const_std::string&_script__:4:13):
+            var y = z + x;
+                    ^^^^^
+    at eval (<anonymous>)
+    at Promise.resolve.then.script (EvalJs-runner.js:2:34)
+)";
+    EXPECT_FALSE(expected_error == result);
+    EXPECT_EQ(expected_error, result.error);
+  }
+}
+
+IN_PROC_BROWSER_TEST_F(EvalJsBrowserTest, EvalJsWithManualReply) {
+  ASSERT_TRUE(embedded_test_server()->Start());
+  NavigateToURL(shell(), embedded_test_server()->GetURL("/title2.html"));
+
+  std::string script = "window.domAutomationController.send(20); 'hi';";
+
+  // Calling domAutomationController is required for EvalJsWithManualReply.
+  EXPECT_EQ(20, EvalJsWithManualReply(shell(), script));
+
+  // Calling domAutomationController is an error with EvalJs.
+  auto result = EvalJs(shell(), script);
+  EXPECT_FALSE(20 == result);
+  EXPECT_FALSE("hi" == result);
+  EXPECT_THAT(result.error,
+              ::testing::StartsWith(
+                  "Internal Error: expected a 2-element list of the form "));
+  EXPECT_THAT(
+      result.error,
+      ::testing::EndsWith("This is potentially because a script tried to call "
+                          "domAutomationController.send itself -- that is only "
+                          "allowed when using EvalJsWithManualReply().  When "
+                          "using EvalJs(), result values are just the result "
+                          "of calling eval() on the script -- the completion "
+                          "value is the value of the last executed statement.  "
+                          "When using ExecJs(), there is no result value."));
+}
+
 }  // namespace content