From 3acdef8ed9063b07c777970b264cef67592f90ee Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= <essen@ninenines.eu>
Date: Tue, 4 Dec 2018 17:32:07 +0100
Subject: Fix and document Dialyzer against beam files

---
 doc/src/guide/dialyzer.asciidoc | 13 +++++++++++++
 plugins/dialyzer.mk             |  2 +-
 test/plugin_dialyzer.mk         | 10 ++++++++--
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/doc/src/guide/dialyzer.asciidoc b/doc/src/guide/dialyzer.asciidoc
index 58fe53f..6031113 100644
--- a/doc/src/guide/dialyzer.asciidoc
+++ b/doc/src/guide/dialyzer.asciidoc
@@ -71,3 +71,16 @@ it doesn't exist. This is normally not necessary as
 Dialyzer creates it automatically.
 
 The PLT file will be removed when you run `make distclean`.
+
+=== Dialyzing beam files
+
+By default Erlang.mk will run Dialyzer against the source
+code. It is possible to configure Erlang.mk to use the
+compiled source files instead. This is done using the
+`DIALYZER_DIRS` variable:
+
+[source,make]
+DIALYZER_DIRS = -r ebin
+
+This value must be set before including Erlang.mk to
+function properly.
diff --git a/plugins/dialyzer.mk b/plugins/dialyzer.mk
index 4c2c81d..41e5871 100644
--- a/plugins/dialyzer.mk
+++ b/plugins/dialyzer.mk
@@ -54,7 +54,7 @@ distclean-plt:
 	$(gen_verbose) rm -f $(DIALYZER_PLT)
 
 ifneq ($(wildcard $(DIALYZER_PLT)),)
-dialyze:
+dialyze: $(if $(filter --src,$(DIALYZER_DIRS)),,deps app)
 else
 dialyze: $(DIALYZER_PLT)
 endif
diff --git a/test/plugin_dialyzer.mk b/test/plugin_dialyzer.mk
index c0229eb..a487fae 100644
--- a/test/plugin_dialyzer.mk
+++ b/test/plugin_dialyzer.mk
@@ -6,7 +6,7 @@ ifneq ($(shell which sem 2>/dev/null),)
 	DIALYZER_MUTEX = sem --fg --id dialyzer
 endif
 
-.PHONY: dialyzer $(C_SRC_TARGETS)
+.PHONY: dialyzer $(DIALYZER_TARGETS)
 
 dialyzer: $(DIALYZER_TARGETS)
 
@@ -109,7 +109,7 @@ dialyzer-beam: build clean
 	$t echo "ERLC_OPTS += +'{parse_transform, lager_transform}'" >> $(APP)/Makefile
 
 	$i "Make Dialyzer use the beam files"
-	$t echo "DIALYZER_DIRS = -r ebin" >> $(APP)/Makefile
+	$t perl -ni.bak -e 'print;if ($$.==1) {print "DIALYZER_DIRS = -r ebin\n"}' $(APP)/Makefile
 
 	$i "Create a module that calls lager"
 	$t printf "%s\n" \
@@ -120,6 +120,12 @@ dialyzer-beam: build clean
 	$i "Run Dialyzer"
 	$t $(DIALYZER_MUTEX) $(MAKE) -C $(APP) dialyze $v
 
+	$i "Clean the application"
+	$t $(MAKE) -C $(APP) clean $v
+
+	$i "Run Dialyzer again using the produced PLT file"
+	$t $(DIALYZER_MUTEX) $(MAKE) -C $(APP) dialyze $v
+
 dialyzer-check: build clean
 
 	$i "Bootstrap a new OTP application named $(APP)"
-- 
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