Record the compilation digest even on webpack error (#2117)

* Record the compilation digest even on webpack error

Fixes /issues/2113

* fix: failed builds should return as fresh

If it returns stale, the error message will never make it to the `webpack-dev-server` overlay. This also fixes typescript related problems in #2113

lib/webpacker/compiler.rb

@@ -19,7 +19,12 @@ def initialize(webpacker)
   def compile
     if stale?
       run_webpack.tap do |success|
-        record_compilation_digest if success
+        # We used to only record the digest on success
+        # However, the output file is still written on error, (at least with ts-loader), meaning that the
+        # digest should still be updated. If it's not, you can end up in a situation where a recompile doesn't
+        # take place when it should.
+        # See https://github.com/rails/webpacker/issues/2113
+        record_compilation_digest
       end
     else
       true

test/compiler_test.rb

@@ -49,14 +49,13 @@ def test_freshness_on_compile_success
     end
   end
 
-  def test_staleness_on_compile_fail
+  def test_freshness_on_compile_fail
     status = OpenStruct.new(success?: false)
 
     assert Webpacker.compiler.stale?
     Open3.stub :capture3, [:sterr, :stdout, status] do
-
       Webpacker.compiler.compile
-      assert Webpacker.compiler.stale?
+      assert Webpacker.compiler.fresh?
     end
   end