Update asset digests when sourcemaps change

When sourcemaps change, their digest will change, and the generated URL in the `# sourceMappingURL` comment will change. Therefore, it's important that the digest of the original asset also changes, so that caches can be invalidated correctly.

This change makes use of the existing `#referenced_by` API in the SourceMappingUrls compiler, and implements the tests in a similar way to 59406ab.

Author: davidtaylorhq

lib/propshaft/compiler/source_mapping_urls.rb

@@ -9,6 +9,14 @@ def compile(asset, input)
     input.gsub(SOURCE_MAPPING_PATTERN) { source_mapping_url(asset.logical_path, asset_path($2, asset.logical_path), $1, $3) }
   end
 
+  def referenced_by(asset, references: Set.new)
+    asset.content.scan(SOURCE_MAPPING_PATTERN).each do |_, source_mapping_url, _|
+      sourcemap_asset = load_path.find(asset_path(source_mapping_url, asset.logical_path))
+      references << sourcemap_asset if sourcemap_asset
+    end
+    references
+  end
+
   private
     def asset_path(source_mapping_url, logical_path)
       source_mapping_url.gsub!(/^(.+\/)?#{url_prefix}\//, "")

test/propshaft/compiler/source_mapping_urls_test.rb

@@ -72,6 +72,24 @@ class Propshaft::Compiler::SourceMappingUrlsTest < ActiveSupport::TestCase
                   compile_asset(find_asset("source.js", fixture_path: "mapped"))
   end
 
+  test "changes to sourcemap are reflected in parent digest" do
+    root_path = Pathname.new("#{__dir__}/../../fixtures/assets/mapped")
+    assembly = Propshaft::Assembly.new(ActiveSupport::OrderedOptions.new.tap { |config|
+      config.paths = [ root_path ]
+      config.compilers = [[ "text/javascript", Propshaft::Compiler::SourceMappingUrls ]]
+    })
+
+    digest = find_asset("source.js", fixture_path: "mapped", load_path: assembly.load_path).digest
+
+    open_asset_with_reset("mapped/source.js.map") do |sourcemap_file|
+      sourcemap_file.write "changes!"
+      sourcemap_file.flush
+
+      new_digest = find_asset("source.js", fixture_path: "mapped", load_path: assembly.load_path).digest
+      assert_not_equal digest, new_digest
+    end
+  end
+
   private
     def compile_asset(asset)
 
@@ -81,6 +99,15 @@ def compile_asset(asset)
 
       assembly.compilers.compile(asset)
     end
+
+    def open_asset_with_reset(logical_path)
+      dependency_path = Pathname.new("#{__dir__}/../../fixtures/assets/#{logical_path}")
+      existing_dependency_content = File.read(dependency_path)
+
+      File.open(dependency_path, "a") { |f| yield f }
+    ensure
+      File.write(dependency_path, existing_dependency_content)
+    end
 end
 
 # //# sourceMappingURL=/assets/sourceMappingURL-already-prefixed.js-[a-z0-9]{40}.map

test/test_helper.rb

@@ -11,10 +11,10 @@
 
 class ActiveSupport::TestCase
   private
-    def find_asset(logical_path, fixture_path:)
+    def find_asset(logical_path, fixture_path:, load_path: nil)
       root_path = Pathname.new("#{__dir__}/fixtures/assets/#{fixture_path}")
       path = root_path.join(logical_path)
-      load_path = Propshaft::LoadPath.new([ root_path ], compilers: Propshaft::Compilers.new(nil))
+      load_path ||= Propshaft::LoadPath.new([ root_path ], compilers: Propshaft::Compilers.new(nil))
 
       Propshaft::Asset.new(path, logical_path: logical_path, load_path: load_path)
     end