Detect and report failure to start the diff-highlight process

NEWS.adoc

@@ -1,6 +1,13 @@
 Release notes
 =============
 
+master
+------
+
+Bug fixes:
+
+ - Add workaround for detecting failure to start the diff-highlight process.
+
 tig-2.2.1
 ---------
 
@@ -25,7 +32,7 @@ Improvements:
  - Bind 'Ctrl-D' and 'Ctrl-U' to half-page movements by default.
  - manual: Mention how to change default Up/Down behavior in diff view.
 
-Bug fixes
+Bug fixes:
 
  - Reorganize checking of libraries for termcap functions.
  - Fix `:goto <id>` error message.

include/tig/diff.h

@@ -37,7 +37,7 @@ void diff_common_select(struct view *view, struct line *line, const char *change
 void diff_save_line(struct view *view, struct diff_state *state, enum open_flags flags);
 void diff_restore_line(struct view *view, struct diff_state *state);
 enum status_code diff_init_highlight(struct view *view, struct diff_state *state);
-void diff_done_highlight(struct diff_state *state);
+bool diff_done_highlight(struct diff_state *state);
 
 unsigned int diff_get_lineno(struct view *view, struct line *line);
 const char *diff_get_pathname(struct view *view, struct line *line);

src/diff.c

@@ -61,13 +61,13 @@ diff_init_highlight(struct view *view, struct diff_state *state)
 	return SUCCESS;
 }
 
-void
+bool
 diff_done_highlight(struct diff_state *state)
 {
-	if (state->highlight) {
-		io_kill(&state->view_io);
-		io_done(&state->view_io);
-	}
+	if (!state->highlight)
+		return true;
+	io_kill(&state->view_io);
+	return io_done(&state->view_io);
 }
 
 struct diff_stat_context {
@@ -424,7 +424,10 @@ diff_read(struct view *view, struct buffer *buf, bool force_stop)
 		return diff_read_describe(view, buf, state);
 
 	if (!buf) {
-		diff_done_highlight(state);
+		if (!diff_done_highlight(state)) {
+			report("Failed run the diff-highlight program: %s", opt_diff_highlight);
+			return false;
+		}
 
 		/* Fall back to retry if no diff will be shown. */
 		if (view->lines == 0 && opt_file_args) {

src/io.c

@@ -179,7 +179,7 @@ io_done(struct io *io)
 	io_init(io);
 
 	while (pid > 0) {
-		int status;
+		int status = 0;
 		pid_t waiting = waitpid(pid, &status, 0);
 
 		if (waiting < 0) {
@@ -189,9 +189,7 @@ io_done(struct io *io)
 			return false;
 		}
 
-		if (WEXITSTATUS(status)) {
-			io->status = WEXITSTATUS(status);
-		}
+		io->status = WIFEXITED(status) ? WEXITSTATUS(status) : 0;
 
 		return waiting == pid &&
 		       !WIFSIGNALED(status) &&
@@ -327,6 +325,8 @@ io_exec(struct io *io, enum io_type type, const char *dir, char * const env[], c
 		}
 
 		execvp(argv[0], (char *const*) argv);
+
+		close(STDOUT_FILENO);
 		exit(errno);
 	}
 

src/stage.c

@@ -566,8 +566,12 @@ stage_read(struct view *view, struct buffer *buf, bool force_stop)
 	if (stage_line_type == LINE_STAT_UNTRACKED)
 		return pager_common_read(view, buf ? buf->data : NULL, LINE_DEFAULT, NULL);
 
-	if (!buf)
-		diff_done_highlight(&state->diff);
+	if (!buf) {
+		if (!diff_done_highlight(&state->diff)) {
+			report("Failed run the diff-highlight program: %s", opt_diff_highlight);
+			return true;
+		}
+	}
 
 	if (!buf && !view->lines && view->parent) {
 		maximize_view(view->parent, true);

test/diff/diff-highlight-test

@@ -4,7 +4,8 @@
 . libgit.sh
 
 file bin/diff-highlight <<EOF
-sed 's/Add type parameter for js.Dynamic/Changed by diff-highlight/'
+#!/bin/sh
+exec sed 's/Add type parameter for js.Dynamic/Changed by diff-highlight/'
 EOF
 
 chmod +x bin/diff-highlight
@@ -20,6 +21,9 @@ steps '
 
 	:set diff-highlight = cat
 	:save-display diff-custom.screen
+
+	:set diff-highlight = program-that-does-not-exist
+	:save-display diff-failure.screen
 '
 
 in_work_dir create_repo_from_tgz "$base_dir/files/scala-js-benchmarks.tgz"
@@ -89,3 +93,35 @@ index 65f914a..3aa4320 100644
 
 [diff] a1dcf1aaa11470978db1d5d8bcf9e16201eb70ff - line 1 of 24              100%
 EOF
+
+assert_equals 'diff-failure.screen' <<EOF
+ 
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+[diff] a1dcf1aaa11470978db1d5d8bcf9e16201eb70ff                               0%
+EOF