fix(isc): retry the DSL grammar when the artifact misparses a source

The shipped isc.artifact.json rejects lowercase system codes that the
Ruby-DSL grammar accepts (acadsin-zho-Hani-Latn-2002.isc) — one bad
map broke every spec that loads the corpus in CI. The runtime now
prefers the artifact and retries through the DSL on ParseFailed; the
artifact recompile via the parsanol toolchain remains the upstream
fix.

Author: ronaldtse

lib/interscript/isc/parser.rb

@@ -34,6 +34,13 @@ def parse_with_callbacks(source, filename: nil)
             parse_with_artifact(source)
           rescue ArtifactUnavailable
             parse_with_dsl(source)
+          rescue Parsanol::ParseFailed
+            # A stale or buggy artifact must not fail a source the DSL
+            # grammar accepts (the acadsin-zho-Hani-Latn-2002 incident:
+            # the shipped artifact rejected lowercase system codes the
+            # DSL handles). Re-parse through the Ruby grammar; the
+            # artifact recompile remains the real fix upstream.
+            parse_with_dsl(source)
           end
           Normalizer.normalize(tree)
         rescue Parsanol::ParseFailed => e

spec/interscript/isc/parser_spec.rb

@@ -80,6 +80,19 @@
       expect(artifact_tree).to eq(dsl_tree)
     end
 
+    it "retries the DSL grammar when the artifact misparses a corpus map" do
+      skip "parsanol lacks PARG (needs >= 1.3.61)" unless Interscript::Isc::Parser.respond_to?(:artifact)
+
+      # Regression guard: a stale/buggy artifact must not fail a source the
+      # DSL grammar handles (acadsin-zho-Hani-Latn-2002.isc did exactly
+      # this — artifact rejected lowercase system codes, DSL accepted).
+      allow(described_class).to receive(:parse_with_artifact)
+        .and_raise(Parsanol::ParseFailed.new("artifact mismatch"))
+      tree = described_class.parse(src)
+      doc = Interscript::Isc::DocumentBuilder.build(tree, filename: "test.isc")
+      expect(doc[:systemCode]).to eq("s")
+    end
+
     it "falls back to the DSL grammar when the artifact cannot load" do
       skip "parsanol lacks PARG (needs >= 1.3.61)" unless Interscript::Isc::Parser.respond_to?(:artifact)