test: use emacsclient(1) for Emacs tests

Before the change, every Emacs test ran in a separate Emacs
instance.  Starting Emacs many times wastes considerable time and
it gets worse as the test suite grows.  The patch solves this by
using a single Emacs server and emacsclient(1) to run multiple
tests.  Emacs server is started on the first test_emacs call and
stopped when test_done is called.  We take care not to leave
orphan Emacs processes behind when test is terminated by whatever
reason: Emacs server runs a watchdog that periodically checks
that the test is still running.

Some tests need to provide user input.  Before the change, this
was done using echo(1) to Emacs stdin.  This no longer works and
instead `standard-input' variable is set accordingly to make
`read' return the appropriate string.

3 files changed, 31 insertions, 16 deletions

diff --git a/test/emacs b/test/emacs
index 3034a5a6..e59de47c 100755
--- a/test/emacs
+++ b/test/emacs
@@ -259,15 +259,15 @@ test_expect_equal_file OUTPUT EXPECTED
 
 test_begin_subtest "Save attachment from within emacs using notmuch-show-save-attachments"
 # save as archive to test that Emacs does not re-compress .gz
-echo ./attachment1.gz |
-test_emacs '(notmuch-show "id:cf0c4d610911171136h1713aa59w9cf9aa31f052ad0a@mail.gmail.com")
-	    (notmuch-show-save-attachments)' > /dev/null 2>&1
+test_emacs '(let ((standard-input "\"attachment1.gz\""))
+	      (notmuch-show "id:cf0c4d610911171136h1713aa59w9cf9aa31f052ad0a@mail.gmail.com")
+	      (notmuch-show-save-attachments))' > /dev/null 2>&1
 test_expect_equal_file attachment1.gz "$EXPECTED/attachment"
 
 test_begin_subtest "Save attachment from within emacs using notmuch-show-save-part"
 # save as archive to test that Emacs does not re-compress .gz
-echo ./attachment2.gz |
-test_emacs '(notmuch-show-save-part "id:cf0c4d610911171136h1713aa59w9cf9aa31f052ad0a@mail.gmail.com" 5)' > /dev/null 2>&1
+test_emacs '(let ((standard-input "\"attachment2.gz\""))
+	      (notmuch-show-save-part "id:cf0c4d610911171136h1713aa59w9cf9aa31f052ad0a@mail.gmail.com" 5))' > /dev/null 2>&1
 test_expect_equal_file attachment2.gz "$EXPECTED/attachment"
 
 test_begin_subtest "View raw message within emacs"
diff --git a/test/test-lib.el b/test/test-lib.el
index 4e7f5cfc..a7839368 100644
--- a/test/test-lib.el
+++ b/test/test-lib.el
@@ -23,6 +23,12 @@
 ;; avoid crazy 10-column default of --batch
 (set-frame-width (window-frame (get-buffer-window)) 80)
 
+;; `read-file-name' by default uses `completing-read' function to read
+;; user input.  It does not respect `standard-input' variable which we
+;; use in tests to provide user input.  So replace it with a plain
+;; `read' call.
+(setq read-file-name-function (lambda (&rest _) (read)))
+
 (defun notmuch-test-wait ()
   "Wait for process completion."
   (while (get-buffer-process (current-buffer))
@@ -51,3 +57,10 @@ FILENAME is OUTPUT."
 	  (setq str (concat str (buffer-substring start next-pos))))
 	(setq start next-pos)))
     str))
+
+(defun orphan-watchdog (pid)
+  "Periodically check that the process with id PID is still
+running, quit if it terminated."
+  (if (not (process-attributes pid))
+      (kill-emacs)
+    (run-at-time "1 min" nil 'orphan-watchdog pid)))
diff --git a/test/test-lib.sh b/test/test-lib.sh
index 7d39d27b..079d7dba 100755
--- a/test/test-lib.sh
+++ b/test/test-lib.sh
@@ -831,6 +831,8 @@ test_done () {
 
 	echo
 
+	[ -n "$EMACS_SERVER" ] && test_emacs '(kill-emacs)'
+
 	if [ "$test_failure" = "0" ]; then
 	    if [ "$test_broken" = "0" ]; then	    
 		rm -rf "$remove_tmp"
@@ -850,16 +852,8 @@ emacs_generate_script () {
 export PATH=$PATH
 export NOTMUCH_CONFIG=$NOTMUCH_CONFIG
 
-# We assume that the user will give a command-line argument only if
-# wanting to run in batch mode.
-if [ \$# -gt 0 ]; then
-	BATCH=--batch
-fi
-
 # Here's what we are using here:
 #
-# --batch:		Quit after given commands and print all (messages)
-#
 # --no-init-file	Don't load users ~/.emacs
 #
 # --no-site-file	Don't load the site-wide startup stuff
@@ -868,16 +862,24 @@ fi
 #
 # --load		Force loading of notmuch.el and test-lib.el
 
-emacs \$BATCH --no-init-file --no-site-file \
+emacs --no-init-file --no-site-file \
 	--directory "$TEST_DIRECTORY/../emacs" --load notmuch.el \
 	--directory "$TEST_DIRECTORY" --load test-lib.el \
-	--eval "(progn \$@)"
+	"\$@"
 EOF
 	chmod a+x "$TMP_DIRECTORY/run_emacs"
 }
 
 test_emacs () {
-	"$TMP_DIRECTORY/run_emacs" "$@"
+	if [ -z "$EMACS_SERVER" ]; then
+		EMACS_SERVER="notmuch-test-suite-$$"
+		"$TMP_DIRECTORY/run_emacs" \
+			--daemon \
+			--eval "(setq server-name \"$EMACS_SERVER\")" \
+			--eval "(orphan-watchdog $$)" || return
+	fi
+
+	emacsclient --socket-name="$EMACS_SERVER" --eval "(progn $@)"
 }