From 8c363688ac173d34c865b8271ade8c845b67fa24 Mon Sep 17 00:00:00 2001
From: Teddy Wing
Date: Mon, 24 Sep 2018 21:34:35 +0200
Subject: Makefile: Only run `xcodebuild` when there are changes

Previously, Make would always run `xcodebuild`. I couldn't figure out
why, but after some looking around and experimenting, it looked to be
due to the `$(RUST_LIB)` prerequisite. Putting it in the order-only
dependencies list seems to fix the never-up-to-date problem.

Also use `:=` instead of `=` when defining `SOURCE_FILES`. During my
research, I came across this recommendation:

> always use := not = for shell (and wildcard, for that matter) for
> performance reasons.

From MadScientist (https://stackoverflow.com/users/939557/madscientist)
on Stack Overflow:
https://stackoverflow.com/questions/26694249/makefiles-using-wildcard-vs-find-for-specifying-source-files/26694693#26694693

Move the `DomeKey` debug product executable path into a variable and use
it as a target to clarify the build target and also allow us to
substitute the variable in the `run` task.

Now finally, `make run` won't re-build the project if no changes have
been made, it'll just run the executable.
---
 Makefile | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

(limited to 'Makefile')

diff --git a/Makefile b/Makefile
index 1a1f35c..687d70a 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-SOURCE_FILES = $(shell find DomeKey lib \
+SOURCE_FILES := $(shell find DomeKey lib \
 	-type f \
 	-name '*.h' \
 	-or -name '*.m' \
@@ -7,9 +7,13 @@ SOURCE_FILES = $(shell find DomeKey lib \
 RUST_DIR := lib/dome-key-map
 RUST_LIB := target/debug/libdome_key_map.a
 
+DEBUG_PRODUCT := ~/Library/Developer/Xcode/DerivedData/DomeKey-*/Build/Products/Debug/DomeKey
+
 
 .PHONY: build
-build: $(SOURCE_FILES) $(RUST_LIB)
+build: $(DEBUG_PRODUCT)
+
+$(DEBUG_PRODUCT): $(SOURCE_FILES) | $(RUST_LIB)
 	xcodebuild -scheme DomeKey -configuration Debug
 
 $(RUST_LIB):
@@ -17,4 +21,4 @@ $(RUST_LIB):
 
 .PHONY: run
 run: build
-	~/Library/Developer/Xcode/DerivedData/DomeKey-*/Build/Products/Debug/DomeKey
+	$(DEBUG_PRODUCT)
-- 
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