Makefile: Track dependencies automatically.

* build-aux/find-dependencies.scm: New file.
* Makefile.am (DOC_IMAGES): Delete variable.
(.depends): New target. Include it in the Makefile.
($(SKRIBILO_BUILD_DIR)/ccwl.info, $(SKRIBILO_BUILD_DIR)/ccwl.html):
Depend on DOC_OTHER_DEPENDENCIES.
(clean-local): Delete .depends.
* .gitignore: Add .depends.

3 files changed, 88 insertions, 6 deletions

diff --git a/.gitignore b/.gitignore
index 83d6491..752eca1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 *.go
+.depends
 Makefile
 Makefile.in
 aclocal.m4
diff --git a/Makefile.am b/Makefile.am
index 3061b74..be17f08 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -66,9 +66,13 @@ EXTRA_DIST +=			\
 # Build documentation
 
 SKRIBILO_BUILD_DIR = $(srcdir)/doc/skribilo
-DOC_IMAGES = $(addprefix $(SKRIBILO_BUILD_DIR)/, \
-  checksum.svg \
-  decompress-compile-run.svg)
+
+.depends: build-aux/find-dependencies.scm doc/ccwl.skb
+	$(AM_V_GEN)$(top_builddir)/pre-inst-env $(GUILE) --no-auto-compile $< > $@
+
+# We prefix with - so that automake does not fail when .depends is
+# missing.
+-include .depends
 
 $(SKRIBILO_BUILD_DIR)/%.cwl: doc/%.scm
 	$(MKDIR_P) $(SKRIBILO_BUILD_DIR)
@@ -88,11 +92,11 @@ $(SKRIBILO_BUILD_DIR)/%.cwl: doc/%.scm
 info-local: $(SKRIBILO_BUILD_DIR)/ccwl.info
 html-local: $(SKRIBILO_BUILD_DIR)/ccwl.html
 
-$(SKRIBILO_BUILD_DIR)/ccwl.info: doc/ccwl.skb ccwl/skribilo.scm $(DOC_IMAGES)
+$(SKRIBILO_BUILD_DIR)/ccwl.info: doc/ccwl.skb ccwl/skribilo.scm $(DOC_IMAGES) $(DOC_OTHER_DEPENDENCIES)
 	$(MKDIR_P) $(SKRIBILO_BUILD_DIR)
 	$(AM_V_GEN)$(top_builddir)/pre-inst-env $(SKRIBILO) -t info $< -o $@
 
-$(SKRIBILO_BUILD_DIR)/ccwl.html: doc/ccwl.skb ccwl/skribilo.scm $(DOC_IMAGES)
+$(SKRIBILO_BUILD_DIR)/ccwl.html: doc/ccwl.skb ccwl/skribilo.scm $(DOC_IMAGES) $(DOC_OTHER_DEPENDENCIES)
 	rm -rf $@
 	$(MKDIR_P) $@
 	$(AM_V_GEN)$(top_builddir)/pre-inst-env $(SKRIBILO) -t html $< -o $@/index.html
@@ -127,4 +131,4 @@ website/manual/dev/en: $(SKRIBILO_BUILD_DIR)/ccwl.html
 # The clean target depends on clean-local. We use clean-local to clean
 # up the website and the skribilo build directory.
 clean-local:
-	rm -rf website/index.html website/manual $(SKRIBILO_BUILD_DIR)
+	rm -rf .depends website/index.html website/manual $(SKRIBILO_BUILD_DIR)
diff --git a/build-aux/find-dependencies.scm b/build-aux/find-dependencies.scm
new file mode 100644
index 0000000..fb68e9c
--- /dev/null
+++ b/build-aux/find-dependencies.scm
@@ -0,0 +1,77 @@
+;;; ccwl --- Concise Common Workflow Language
+;;; Copyright © 2021 Arun Isaac <arunisaac@systemreboot.net>
+;;;
+;;; This file is part of ccwl.
+;;;
+;;; ccwl is free software: you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation, either version 3 of the License, or
+;;; (at your option) any later version.
+;;;
+;;; ccwl is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with ccwl.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This script scans source files and prints dependencies for make to
+;; pick up.
+
+;;; Code:
+
+(use-modules (srfi srfi-1)
+             (srfi srfi-171)
+             (ice-9 match)
+             (skribilo reader skribe))
+
+(define (skribilo-document file)
+  "Read skribilo FILE and return the document form."
+  (call-with-input-file file
+    (lambda (port)
+      (port-transduce (tfilter (match-lambda
+                                 (('document _ ...) #t)
+                                 (_ #f)))
+                      (rany identity)
+                      (make-skribe-reader)
+                      port))))
+
+(define (find-dependencies document)
+  "Return a list of dependencies of the skribilo form DOCUMENT. Each
+dependency is of the form (tag . file). tag may either be the symbol
+'image or the symbol 'other."
+  (match document
+    (('image args ...)
+     (apply (lambda* (#:key file #:allow-other-keys)
+              `((image . ,file)))
+            args))
+    (('source args ...)
+     (apply (lambda* (#:key file #:allow-other-keys)
+              `((other . ,file)))
+            args))
+    (('scheme-source file)
+     `((other . ,file)))
+    (('source-ref file _ ...)
+     `((other . ,file)))
+    ((elements ...)
+     (append-map find-dependencies elements))
+    (atom '())))
+
+;; Print dependencies
+(let ((dependencies
+       (find-dependencies (skribilo-document "doc/ccwl.skb"))))
+  (format #t "DOC_IMAGES = ~a~%"
+          (string-join (filter-map (match-lambda
+                                     (('image . file) file)
+                                     (_ #f))
+                                   dependencies)
+                       " "))
+  (format #t "DOC_OTHER_DEPENDENCIES = ~a~%"
+          (string-join (filter-map (match-lambda
+                                     (('other . file) file)
+                                     (_ #f))
+                                   dependencies)
+                       " ")))