From d47a5275538f1c0ed2a4f3acff19809ebb5f59c7 Mon Sep 17 00:00:00 2001
From: Jacob MacDonald <jakemac@google.com>
Date: Wed, 30 Aug 2023 13:31:49 -0700
Subject: [PATCH] Check if we can read assets before asking for their digests
 (#3566)

---
 build_resolvers/CHANGELOG.md     |  5 +++++
 build_resolvers/lib/builder.dart | 13 ++++++++-----
 build_resolvers/pubspec.yaml     |  2 +-
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/build_resolvers/CHANGELOG.md b/build_resolvers/CHANGELOG.md
index 98fafd65d..57ecfe63e 100644
--- a/build_resolvers/CHANGELOG.md
+++ b/build_resolvers/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 2.3.1
+
+- Fix a bug in the transitive digest builder, ensure we check if assets are
+  readable before asking for their digest.
+
 ## 2.3.0
 
 - Improve performance for resolves by adding a builder which serializes
diff --git a/build_resolvers/lib/builder.dart b/build_resolvers/lib/builder.dart
index 2fe514d5f..04b0359fb 100644
--- a/build_resolvers/lib/builder.dart
+++ b/build_resolvers/lib/builder.dart
@@ -37,11 +37,8 @@ class _TransitiveDigestsBuilder extends Builder {
         continue;
       }
 
-      // Otherwise, add its digest and queue all its dependencies to crawl.
-      byteSink.add((await buildStep.digest(next)).bytes);
-      final deps = await dependenciesOf(next, buildStep);
-      if (deps == null) {
-        // We warn here but do not fail, the downside is slower builds.
+      // We warn here but do not fail, the downside is slower builds.
+      if (!(await buildStep.canRead(next))) {
         log.warning('''
 Unable to read asset, could not compute transitive deps: $next
 
@@ -50,6 +47,12 @@ https://github.com/dart-lang/build/blob/master/docs/faq.md#unable-to-read-asset-
         return;
       }
 
+      // Otherwise, add its digest and queue all its dependencies to crawl.
+      byteSink.add((await buildStep.digest(next)).bytes);
+
+      // We know this isn't null since we already checked if we can read `next`.
+      final deps = (await dependenciesOf(next, buildStep))!;
+
       // Add all previously unseen deps to the queue.
       for (final dep in deps) {
         if (seen.add(dep)) queue.add(dep);
diff --git a/build_resolvers/pubspec.yaml b/build_resolvers/pubspec.yaml
index 157ff7917..872c99f42 100644
--- a/build_resolvers/pubspec.yaml
+++ b/build_resolvers/pubspec.yaml
@@ -1,5 +1,5 @@
 name: build_resolvers
-version: 2.3.0
+version: 2.3.1
 description: Resolve Dart code in a Builder
 repository: https://github.com/dart-lang/build/tree/master/build_resolvers