Makefile for use with PlantUML diagrams

Makefile

PLANTUML_JAR_URL = https://sourceforge.net/projects/plantuml/files/plantuml.jar/download
DIAGRAMS_SRC := $(wildcard diagrams/*.plantuml)
DIAGRAMS_PNG := $(addsuffix .png, $(basename $(DIAGRAMS_SRC)))
DIAGRAMS_SVG := $(addsuffix .svg, $(basename $(DIAGRAMS_SRC)))

# Default target first; build PNGs, probably what we want most of the time
png: plantuml.jar $(DIAGRAMS_PNG)

# SVG are nice-to-have but don't need to build by default
svg: plantuml.jar $(DIAGRAMS_SVG)

# clean up compiled files
clean:
	rm -f plantuml.jar $(DIAGRAMS_PNG) $(DIAGRAMS_SVG)

# If the JAR file isn't already present, download it
plantuml.jar:
	curl -sSfL $(PLANTUML_JAR_URL) -o plantuml.jar

# Each PNG output depends on its corresponding .plantuml file
diagrams/%.png: diagrams/%.plantuml 
	java -jar plantuml.jar -tpng $^

# Each SVG output depends on its corresponding .plantuml file
diagrams/%.svg: diagrams/%.plantuml 
	java -jar plantuml.jar -tsvg $^

# Quirk of GNU Make: https://www.gnu.org/software/make/manual/html_node/Phony-Targets.html
.PHONY: png svg clean

Assumptions

• GNU make installed — (dnf|apt|yum) install make or install the Apple developer tools on Mac
• Graphviz installed — (dnf|apt|yum) install graphviz or brew install graphviz on Mac
• A working Java install — varies too much by platform, dnf install java-1.8.0-openjdk on Fedora
• One diagram per file; files have the .plantuml extension and live in the diagrams/ directory relative to this Makefile

Example usage

$ tree docs/
docs/
├── diagrams
│   ├── components.plantuml
│   ├── seq-request-a.plantuml
│   ├── seq-session-create.plantuml
├── Makefile
└── Intro.md

$ cd docs
$ make
    ...make downloads the .jar file
    ...make compiles PNG files by default; use `make svg` for SVG files

$ tree
.
├── diagrams
│   ├── components.plantuml
│   ├── components.png
│   ├── seq-request-a.plantuml
│   ├── seq-request-a.png
│   ├── seq-session-create.plantuml
│   ├── seq-session-create.png
├── Makefile
└── Intro.md

Note: you'll probably want to add plantuml.jar to your .gitignore file.