Don't use the isolate compilation cache for REPL mode scripts

The compilation cache doesn't know about REPL mode. This means that
non-REPL mode compiled scripts are successfully found for their
REPL mode equivalent and vice versa.

This CL disables the compilation cache for REPL mode scripts.
Performance is not really a concern as DevTools console inputs
are usually very small.

R=leszeks@chromium.org

Bug: chromium:1108021
Change-Id: If396c7aa004188730762e4f6bd01dae2fc141181
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2434333
Commit-Queue: Simon Zünd <szuend@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70160}

src/codegen/compiler.cc

@@ -2604,10 +2604,13 @@ MaybeHandle<SharedFunctionInfo> Compiler::GetSharedFunctionInfoForScript(
   LanguageMode language_mode = construct_language_mode(FLAG_use_strict);
   CompilationCache* compilation_cache = isolate->compilation_cache();
 
-  // Do a lookup in the compilation cache but not for extensions.
+  // For extensions or REPL mode scripts neither do a compilation cache lookup,
+  // nor put the compilation result back into the cache.
+  const bool use_compilation_cache =
+      extension == nullptr && script_details.repl_mode == REPLMode::kNo;
   MaybeHandle<SharedFunctionInfo> maybe_result;
   IsCompiledScope is_compiled_scope;
-  if (extension == nullptr) {
+  if (use_compilation_cache) {
     bool can_consume_code_cache =
         compile_options == ScriptCompiler::kConsumeCodeCache;
     if (can_consume_code_cache) {
@@ -2673,7 +2676,7 @@ MaybeHandle<SharedFunctionInfo> Compiler::GetSharedFunctionInfoForScript(
 
     // Add the result to the isolate cache.
     Handle<SharedFunctionInfo> result;
-    if (extension == nullptr && maybe_result.ToHandle(&result)) {
+    if (use_compilation_cache && maybe_result.ToHandle(&result)) {
       DCHECK(is_compiled_scope.is_compiled());
       compilation_cache->PutScript(source, isolate->native_context(),
                                    language_mode, result);

test/inspector/runtime/evaluate-repl-mode-code-cache-expected.txt

+Tests that Runtime.evaluate's REPL mode correctly interacts with the compliation cache (crbug.com/1108021)
+Prefill the cache with non-REPL mode script
+{
+    id : <messageId>
+    result : {
+        result : {
+            description : 8
+            type : number
+            value : 8
+        }
+    }
+}
+REPL mode scripts always return a Promise.
+The first script only returns "8" instead. When the inspector doesn't find a promise (due to a cache hit), it would respond with "undefined".
+{
+    id : <messageId>
+    result : {
+        result : {
+            description : 8
+            type : number
+            value : 8
+        }
+    }
+}

test/inspector/runtime/evaluate-repl-mode-code-cache.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+let {Protocol} = InspectorTest.start(
+  "Tests that Runtime.evaluate's REPL mode correctly interacts with the compliation cache (crbug.com/1108021)");
+
+(async function() {
+  InspectorTest.log('Prefill the cache with non-REPL mode script');
+  InspectorTest.logMessage(await Protocol.Runtime.evaluate({
+    expression: '5 + 3',
+    replMode: false,
+  }));
+
+  InspectorTest.log('REPL mode scripts always return a Promise.')
+  InspectorTest.log('The first script only returns "8" instead. When the inspector doesn\'t find a promise (due to a cache hit), it would respond with "undefined".');
+  InspectorTest.logMessage(await Protocol.Runtime.evaluate({
+    expression: '5 + 3',
+    replMode: true,
+  }));
+
+  InspectorTest.completeTest();
+})();