Make

README.md

This doesn't work

The Problem: No Timestamp Comparison for Generated Files: The rules for $(STYX_SUBSCRIBER_PROTO_JAVA_SRC) and $(STYX_READER_PROTO_JAVA_SRC) specify the .proto files as prerequisites, but the targets themselves are lists of files, for example:

STYX_READER_PROTO_JAVA_SRC = \
	java-src/gen/styx/reader/StyxReader.java \
	java-src/gen/styx/reader/FIBGrpc.java

Make does not expand wildcards in the target name, so the target is literally the string java-src/gen/styx/reader/StyxReader.java java-src/gen/styx/reader/FIBGrpc.java

Makefile

JAVA_TIMESTAMP_FILE = .java-build-timestamp
STYX_SUBSCRIBER_PROTO_SRC = proto/styx.proto
STYX_READER_PROTO_SRC = proto/styx-reader.proto
STYX_SUBSCRIBER_PROTO_JAVA_SRC = \
	java-src/gen/styx/subscriber/StyxReader.java \
	java-src/gen/styx/subscriber/FIBGrpc.java
STYX_READER_PROTO_JAVA_SRC = \
	java-src/gen/styx/reader/StyxReader.java \
	java-src/gen/styx/reader/FIBGrpc.java

PROTOC_GEN_GRPC_JAVA := $(shell which protoc-gen-grpc-java)

# Check if the executable was found and error if not
ifeq ($(PROTOC_GEN_GRPC_JAVA),)
  $(error protoc-gen-grpc-java not found in PATH)
endif

PROTOC_CMD=protoc --plugin=protoc-gen-grpc-java=$(PROTOC_GEN_GRPC_JAVA) \
                  --java_out=java-src \
                  --grpc-java_out=java-src \
                  --proto_path=proto

$(STYX_READER_PROTO_JAVA_SRC): $(STYX_READER_PROTO_SRC)
	mkdir -p java-src
	$(PROTOC_CMD) $<
	
$(STYX_SUBSCRIBER_PROTO_JAVA_SRC): $(STYX_SUBSCRIBER_PROTO_SRC)
	mkdir -p java-src
	$(PROTOC_CMD) $<
	
# Use marker file, both for ease of making this makefile and because it generates dozens of files
java: $(JAVA_TIMESTAMP_FILE)
	
$(JAVA_TIMESTAMP_FILE): $(STYX_SUBSCRIBER_PROTO_JAVA_SRC) $(STYX_READER_PROTO_JAVA_SRC)
	@echo "Building java sources"
	clj -T:build compile-java
	@touch $(JAVA_TIMESTAMP_FILE)