emacs: Use async process helper for search

Previously, search started the async notmuch process directly.  Now,
it uses `notmuch-start-notmuch'.  This simplifies the process sentinel
a bit and means that we no longer have to worry about errors
interleaved with the JSON output.

We also update the tests of Emacs error handling, since the error
output is now separated from the search results buffer.

emacs/notmuch.el

@@ -653,15 +653,8 @@ of the result."
 		    ;; For version mismatch, there's no point in
 		    ;; showing the search buffer
 		    (when (or (= exit-status 20) (= exit-status 21))
-		      (kill-buffer))
-		    (condition-case err
-			(notmuch-check-async-exit-status proc msg)
-		      ;; Suppress the error signal since strange
-		      ;; things happen if a sentinel signals.  Mimic
-		      ;; the top-level's handling of error messages.
-		      (error
-		       (message "%s" (error-message-string err))
-		       (throw 'return nil)))
+		      (kill-buffer)
+		      (throw 'return nil))
 		    (if (and atbob
 			     (not (string= notmuch-search-target-thread "found")))
 			(set 'never-found-target-thread t)))))
@@ -938,10 +931,9 @@ Other optional parameters are used as follows:
       (erase-buffer)
       (goto-char (point-min))
       (save-excursion
-	(let ((proc (start-process
-		     "notmuch-search" buffer
-		     notmuch-command "search"
-		     "--format=json" "--format-version=1"
+	(let ((proc (notmuch-start-notmuch
+		     "notmuch-search" buffer #'notmuch-search-process-sentinel
+		     "search" "--format=json" "--format-version=1"
 		     (if oldest-first
 			 "--sort=oldest-first"
 		       "--sort=newest-first")
@@ -951,7 +943,6 @@ Other optional parameters are used as follows:
 	      ;; should be called no matter how the process dies.
 	      (parse-buf (generate-new-buffer " *notmuch search parse*")))
 	  (process-put proc 'parse-buf parse-buf)
-	  (set-process-sentinel proc 'notmuch-search-process-sentinel)
 	  (set-process-filter proc 'notmuch-search-process-filter)
 	  (set-process-query-on-exit-flag proc nil))))
     (run-hooks 'notmuch-search-hook)))

test/emacs

@@ -855,11 +855,10 @@ test_expect_success "Rendering HTML mail with images" \
     'cat OUTPUT && grep -q smiley OUTPUT'
 
 
-test_begin_subtest "Search handles subprocess errors"
+test_begin_subtest "Search handles subprocess error exit codes"
 cat > notmuch_fail <<EOF
 #!/bin/sh
 echo This is output
-echo This is an error >&2
 exit 1
 EOF
 chmod a+x notmuch_fail
@@ -876,8 +875,6 @@ sed -i -e 's/^\[.*\]$/[XXX]/' ERROR
 test_expect_equal "$(cat OUTPUT; echo ---; cat MESSAGES; echo ---; cat ERROR)" "\
 Error: Unexpected output from notmuch search:
 This is output
-Error: Unexpected output from notmuch search:
-This is an error
 End of search results.
 ---
 $PWD/notmuch_fail exited with status 1 (see *Notmuch errors* for more details)
@@ -887,4 +884,35 @@ $PWD/notmuch_fail exited with status 1
 command: $PWD/notmuch_fail search --format\=json --format-version\=1 --sort\=newest-first tag\:inbox
 exit status: 1"
 
+test_begin_subtest "Search handles subprocess warnings"
+cat > notmuch_fail <<EOF
+#!/bin/sh
+echo This is output
+echo This is a warning >&2
+echo This is another warning >&2
+exit 0
+EOF
+chmod a+x notmuch_fail
+test_emacs "(let ((notmuch-command \"$PWD/notmuch_fail\"))
+	       (with-current-buffer \"*Messages*\" (erase-buffer))
+	       (with-current-buffer \"*Notmuch errors*\" (erase-buffer))
+	       (notmuch-search \"tag:inbox\")
+	       (notmuch-test-wait)
+	       (with-current-buffer \"*Messages*\"
+		  (test-output \"MESSAGES\"))
+	       (with-current-buffer \"*Notmuch errors*\"
+		  (test-output \"ERROR\"))
+	       (test-output))"
+sed -i -e 's/^\[.*\]$/[XXX]/' ERROR
+test_expect_equal "$(cat OUTPUT; echo ---; cat MESSAGES; echo ---; cat ERROR)" "\
+Error: Unexpected output from notmuch search:
+This is output
+End of search results.
+---
+This is a warning (see *Notmuch errors* for more details)
+---
+[XXX]
+This is a warning
+This is another warning"
+
 test_done