Install gsed on macOS in CI, revert Makefile gsed check

- Add step to install GNU sed via brew on macOS runners
- Revert Makefile to original gsed check at parse time

Author: dannywillems

.github/workflows/actions.yml

@@ -15,6 +15,9 @@ jobs:
       - uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python-version }}
+      - name: Install GNU sed on macOS
+        if: runner.os == 'macOS'
+        run: brew install gnu-sed
       - name: Install poetry
         run: pip install poetry==${{ matrix.poetry-version}}
       - name: Install deps

Makefile

@@ -60,29 +60,30 @@ clean: ## Clean build artifacts
 	find . -type f -name "*.pyc" -delete 2>/dev/null || true
 
 # Trailing whitespace targets
-# Note: fix-trailing-whitespace requires GNU sed (gsed) on macOS
+UNAME_S := $(shell uname -s)
+ifeq ($(UNAME_S),Darwin)
+    SED := $(shell command -v gsed 2>/dev/null)
+    ifeq ($(SED),)
+        $(error GNU sed (gsed) not found on macOS. Install with: brew install gnu-sed)
+    endif
+else
+    SED := sed
+endif
+
 .PHONY: fix-trailing-whitespace
 fix-trailing-whitespace: ## Remove trailing whitespaces from all files
-	@if [ "$$(uname -s)" = "Darwin" ]; then \
-		SED=$$(command -v gsed 2>/dev/null); \
-		if [ -z "$$SED" ]; then \
-			echo "Error: GNU sed (gsed) not found on macOS."; \
-			echo "Install with: brew install gnu-sed"; \
-			exit 1; \
-		fi; \
-	else \
-		SED=sed; \
-	fi; \
-	echo "Removing trailing whitespaces from all files..."; \
-	find . -type f \( \
+	@echo "Removing trailing whitespaces from all files..."
+	@find . -type f \( \
 		-name "*.py" -o -name "*.toml" -o -name "*.md" -o -name "*.yaml" \
 		-o -name "*.yml" -o -name "*.json" \) \
 		-not -path "./.git/*" \
 		-not -path "./.mypy_cache/*" \
 		-not -path "./.pytest_cache/*" \
 		-not -path "./.ruff_cache/*" \
-		-exec sh -c "$$SED -i -e 's/[[:space:]]*$$//' \"\$$1\"" _ {} \; && \
-	echo "Trailing whitespaces removed."
+		-exec sh -c \
+			'$(SED) -i -e "s/[[:space:]]*$$//" "$$1"' \
+			_ {} \; && \
+		echo "Trailing whitespaces removed."
 
 .PHONY: check-trailing-whitespace
 check-trailing-whitespace: ## Check for trailing whitespaces in source files