Add GitHub Actions CI workflow for Go (#3)

* Add GitHub Actions workflow for Go build and test

Runs `make parser` to generate the yacc-derived parser sources, then
`go build ./...` and `go test ./...` on push and pull_request.

* Run Go workflow on all pull requests

* Fix Makefile paths after parser sources moved into parser/

The .y grammars and generated .go files now live in parser/, so update
the parser, generate, fmt, and clean targets to point at the new
locations. The %arser.go pattern rule didn't compose cleanly with a
directory prefix, so it's split into explicit parser/parser.go and
parser/hintparser.go rules. genkeyword is built into parser/ so the
//go:generate ./genkeyword directive in parser/generate.go resolves.

* Fail CI when committed parser sources are out of date

Regenerate parser.go and hintparser.go from the .y grammars on every
run, then `git diff --exit-code` against the working tree. If the
committed files don't match a fresh `make parser`, the job fails with
a hint to rerun and commit.

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: kyleconroy

.github/workflows/go.yml

@@ -0,0 +1,35 @@
+name: Go
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25'
+
+      - name: Regenerate parser
+        run: |
+          rm -f parser/parser.go parser/hintparser.go
+          make parser
+
+      - name: Verify parser is up to date
+        run: |
+          if ! git diff --exit-code -- parser/parser.go parser/hintparser.go; then
+            echo "::error::Generated parser files are out of date. Run 'make parser' and commit the result."
+            exit 1
+          fi
+
+      - name: Build
+        run: go build ./...
+
+      - name: Test
+        run: go test ./...

Makefile

@@ -5,32 +5,36 @@ all: fmt parser generate
 test: fmt parser
 	sh test.sh
 
-parser: parser.go hintparser.go
+parser: parser/parser.go parser/hintparser.go
 
 genkeyword: generate_keyword/genkeyword.go
-	go build -C generate_keyword -o ../genkeyword
+	go build -C generate_keyword -o ../parser/genkeyword
 
-generate: genkeyword parser.y
-	go generate
+generate: genkeyword parser/parser.y
+	go generate ./parser/...
 
-%arser.go: prefix = $(@:parser.go=)
-%arser.go: %arser.y bin/goyacc
-	@echo "bin/goyacc -o $@ -p yy$(prefix) -t $(prefix)Parser $<"
-	@bin/goyacc -o $@ -p yy$(prefix) -t $(prefix)Parser $< || ( rm -f $@ && echo 'Please check y.output for more information' && exit 1 )
+parser/parser.go: parser/parser.y bin/goyacc
+	@echo "bin/goyacc -o $@ -p yy -t Parser $<"
+	@bin/goyacc -o $@ -p yy -t Parser $< || ( rm -f $@ && echo 'Please check y.output for more information' && exit 1 )
 	@rm -f y.output
 
-%arser_golden.y: %arser.y
+parser/hintparser.go: parser/hintparser.y bin/goyacc
+	@echo "bin/goyacc -o $@ -p yyhint -t hintParser $<"
+	@bin/goyacc -o $@ -p yyhint -t hintParser $< || ( rm -f $@ && echo 'Please check y.output for more information' && exit 1 )
+	@rm -f y.output
+
+parser/%arser_golden.y: parser/%arser.y
 	@bin/goyacc -fmt -fmtout $@ $<
 	@(git diff --no-index --exit-code $< $@ && rm $@) || (mv $@ $< && >&2 echo "formatted $<" && exit 1)
 
 bin/goyacc: goyacc/main.go goyacc/format_yacc.go
 	GO111MODULE=on go build -o bin/goyacc goyacc/main.go goyacc/format_yacc.go
 
-fmt: bin/goyacc parser_golden.y hintparser_golden.y
+fmt: bin/goyacc parser/parser_golden.y parser/hintparser_golden.y
 	@echo "gofmt (simplify)"
 	@gofmt -s -l -w . 2>&1 | awk '{print} END{if(NR>0) {exit 1}}'
 
 clean:
 	go clean -i ./...
 	rm -rf *.out
-	rm -f parser.go hintparser.go
+	rm -f parser/parser.go parser/hintparser.go parser/genkeyword