From fd5140d49142ec0e68dfbcb98e1053c09dc857b8 Mon Sep 17 00:00:00 2001
From: Clement Skau <cskau@google.com>
Date: Wed, 5 Aug 2020 11:46:28 +0000
Subject: [PATCH] [SDK] Fix VM/kernel version mix in build.

Several people have experienced build issues traced back to
target `//utils/dartanalyzer:generate_summary_strong`.
The issue is triggered by the sdk_hash changing with an old
kernel-service snapshot in the out/ folder.
`generate_summary_strong` uses but does not explicitly depend on
the kernel-service, causing the outdated dependency.
This then causes 'Unexpected Kernel SDK Version' when the new dart
binary tried to load the old kernel-service snapshot.

Tested:
1. Clean build of create_sdk at HEAD.
2. Empty `git commit --amend` to modify commit and thus sdk hash.
3. Rebuild of create_sdk (which failed before).

Cq-Include-Trybots: dart/try:analyzer-analysis-server-linux-try,analyzer-linux-release-try,analyzer-mac-release-try,analyzer-nnbd-linux-release-try,analyzer-win-release-try,benchmark-linux-try,dart-sdk-linux-try,dart-sdk-mac-try,dart-sdk-win-try,dart-sdk-win-try,flutter-analyze-try,front-end-linux-release-x64-try,pkg-linux-release-try,vm-kernel-linux-release-x64-try
Change-Id: Iba07e9d0c5daa7a93870fb501d9bb57682c88a5d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/156913
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Commit-Queue: Clement Skau <cskau@google.com>
---
 build/dart/dart_action.gni     | 15 +++++++++++++++
 utils/application_snapshot.gni |  5 +++++
 2 files changed, 20 insertions(+)

diff --git a/build/dart/dart_action.gni b/build/dart/dart_action.gni
index 2058f0334c3..c357aad4d99 100644
--- a/build/dart/dart_action.gni
+++ b/build/dart/dart_action.gni
@@ -288,6 +288,10 @@ template("_built_tool_action") {
 #  script:
 #    The un-rebased path to the Dart script.
 #
+#  dfe (optional):
+#    Sets the DFE file used by Dart. If not set the VM will attempt to load it
+#    from a snapshot, or fall back on its built-in kernel.
+#
 #  vm_args (optional):
 #    Arguments to pass to the Dart VM.
 #
@@ -323,6 +327,17 @@ template("dart_action") {
                                "visibility",
                                "vm_args",
                              ])
+
+      # Dart has an implicit dependency on the kernel service so unless DFE is
+      # passed, we need to add this dep.
+      if (defined(invoker.dfe)) {
+        vm_args += [ "--dfe=" + rebase_path(invoker.dfe) ]
+      } else {
+        if (!defined(invoker.deps)) {
+          deps = []
+        }
+        deps += [ "$_dart_root/utils/kernel-service:kernel-service" ]
+      }
     }
   } else {
     prebuilt_dart_action(target_name) {
diff --git a/utils/application_snapshot.gni b/utils/application_snapshot.gni
index 7d981bd728a..81ec5eed094 100644
--- a/utils/application_snapshot.gni
+++ b/utils/application_snapshot.gni
@@ -134,6 +134,7 @@ template("_application_snapshot") {
     args += [ rebase_path(main_dart) ]
   }
 
+  # Create a snapshot from kernel built above.
   dart_action(target_name) {
     deps = extra_deps + [ ":${target_name}_dill" ]
     depfile = "$output.d"
@@ -144,6 +145,10 @@ template("_application_snapshot") {
 
     outputs = [ output ]
 
+    # Explicitly set DFE so Dart doesn't implicitly depend on the kernel service
+    # snapshot (creating a circular dep. for kernel-service_snapshot).
+    dfe = "$_dart_root/pkg/vm/bin/kernel_service.dart"
+
     abs_depfile = rebase_path(depfile)
     abs_output = rebase_path(output, root_build_dir)