[PATCH v3 1/6] run-command: add pipe_output_fn to run_processes_parallel_opts

[Calvin Wan <calvinwan@google.com>]

Add pipe_output_fn as an optionally set function in
run_process_parallel_opts. If set, output from each child process is
first separately stored in 'out' and then piped to the callback
function when the child process finishes to allow for separate parsing.

Two of the tests check for line count rather than an exact match
since the interleaved output order is not guaranteed to be exactly
the same every run through.

Signed-off-by: Calvin Wan <calvinwan@google.com>
---
 run-command.c               | 21 +++++++++++++++++++--
 run-command.h               | 21 +++++++++++++++++++++
 t/helper/test-run-command.c | 13 +++++++++++++
 t/t0061-run-command.sh      | 30 ++++++++++++++++++++++++++++++
 4 files changed, 83 insertions(+), 2 deletions(-)

diff --git a/run-command.c b/run-command.c
index c772acd743..03787bc7f5 100644
--- a/run-command.c
+++ b/run-command.c
@@ -1503,6 +1503,7 @@ struct parallel_processes {
 		enum child_state state;
 		struct child_process process;
 		struct strbuf err;
+		struct strbuf out;
 		void *data;
 	} *children;
 	/*
@@ -1560,6 +1561,9 @@ static void pp_init(struct parallel_processes *pp,
 
 	if (!opts->get_next_task)
 		BUG("you need to specify a get_next_task function");
+	
+	if (opts->pipe_output && opts->ungroup)
+		BUG("pipe_output and ungroup are incompatible with each other");
 
 	CALLOC_ARRAY(pp->children, n);
 	if (!opts->ungroup)
@@ -1567,6 +1571,8 @@ static void pp_init(struct parallel_processes *pp,
 
 	for (size_t i = 0; i < n; i++) {
 		strbuf_init(&pp->children[i].err, 0);
+		if (opts->pipe_output)
+			strbuf_init(&pp->children[i].out, 0);
 		child_process_init(&pp->children[i].process);
 		if (pp->pfd) {
 			pp->pfd[i].events = POLLIN | POLLHUP;
@@ -1586,6 +1592,7 @@ static void pp_cleanup(struct parallel_processes *pp,
 	trace_printf("run_processes_parallel: done");
 	for (size_t i = 0; i < opts->processes; i++) {
 		strbuf_release(&pp->children[i].err);
+		strbuf_release(&pp->children[i].out);
 		child_process_clear(&pp->children[i].process);
 	}
 
@@ -1680,8 +1687,12 @@ static void pp_buffer_stderr(struct parallel_processes *pp,
 	for (size_t i = 0; i < opts->processes; i++) {
 		if (pp->children[i].state == GIT_CP_WORKING &&
 		    pp->pfd[i].revents & (POLLIN | POLLHUP)) {
-			int n = strbuf_read_once(&pp->children[i].err,
-						 pp->children[i].process.err, 0);
+			struct strbuf buf = STRBUF_INIT;
+			int n = strbuf_read_once(&buf, pp->children[i].process.err, 0);
+			strbuf_addbuf(&pp->children[i].err, &buf);
+			if (opts->pipe_output)
+				strbuf_addbuf(&pp->children[i].out, &buf);
+			strbuf_release(&buf);
 			if (n == 0) {
 				close(pp->children[i].process.err);
 				pp->children[i].state = GIT_CP_WAIT_CLEANUP;
@@ -1717,6 +1728,12 @@ static int pp_collect_finished(struct parallel_processes *pp,
 		if (i == opts->processes)
 			break;
 
+		if (opts->pipe_output) {
+			opts->pipe_output(&pp->children[i].out, opts->data,
+					  pp->children[i].data);
+			strbuf_reset(&pp->children[i].out);
+		}
+
 		code = finish_command(&pp->children[i].process);
 
 		if (opts->task_finished)
diff --git a/run-command.h b/run-command.h
index e3e1ea01ad..b4584c3698 100644
--- a/run-command.h
+++ b/run-command.h
@@ -440,6 +440,21 @@ typedef int (*start_failure_fn)(struct strbuf *out,
 				void *pp_cb,
 				void *pp_task_cb);
 
+/**
+ * This callback is called on every child process that finished processing.
+ * 
+ * "struct strbuf *process_out" contains the output from the finished child
+ * process.
+ *
+ * pp_cb is the callback cookie as passed into run_processes_parallel,
+ * pp_task_cb is the callback cookie as passed into get_next_task_fn.
+ *
+ * This function is incompatible with "ungroup"
+ */
+typedef void (*pipe_output_fn)(struct strbuf *process_out,
+			       void *pp_cb,
+			       void *pp_task_cb);
+
 /**
  * This callback is called on every child process that finished processing.
  *
@@ -493,6 +508,12 @@ struct run_process_parallel_opts
 	 */
 	start_failure_fn start_failure;
 
+	/**
+	 * pipe_output: See pipe_output_fn() above. This should be
+	 * NULL unless process specific output is needed
+	 */
+	pipe_output_fn pipe_output;
+
 	/**
 	 * task_finished: See task_finished_fn() above. This can be
 	 * NULL to omit any special handling.
diff --git a/t/helper/test-run-command.c b/t/helper/test-run-command.c
index 3ecb830f4a..e9b41419a0 100644
--- a/t/helper/test-run-command.c
+++ b/t/helper/test-run-command.c
@@ -52,6 +52,13 @@ static int no_job(struct child_process *cp,
 	return 0;
 }
 
+static void pipe_output(struct strbuf *process_out,
+			void *pp_cb,
+			void *pp_task_cb)
+{
+	fprintf(stderr, "%s", process_out->buf);
+}
+
 static int task_finished(int result,
 			 struct strbuf *err,
 			 void *pp_cb,
@@ -439,6 +446,12 @@ int cmd__run_command(int argc, const char **argv)
 		opts.ungroup = 1;
 	}
 
+	if (!strcmp(argv[1], "--pipe-output")) {
+		argv += 1;
+		argc -= 1;
+		opts.pipe_output = pipe_output;
+	}
+
 	jobs = atoi(argv[2]);
 	strvec_clear(&proc.args);
 	strvec_pushv(&proc.args, (const char **)argv + 3);
diff --git a/t/t0061-run-command.sh b/t/t0061-run-command.sh
index 7b5423eebd..e50e57db89 100755
--- a/t/t0061-run-command.sh
+++ b/t/t0061-run-command.sh
@@ -134,6 +134,12 @@ test_expect_success 'run_command runs in parallel with more jobs available than
 	test_cmp expect actual
 '
 
+test_expect_success 'run_command runs in parallel with more jobs available than tasks --pipe-output' '
+	test-tool run-command --pipe-output run-command-parallel 5 sh -c "printf \"%s\n%s\n\" Hello World" >out 2>err &&
+	test_must_be_empty out &&
+	test_line_count = 20 err
+'
+
 test_expect_success 'run_command runs ungrouped in parallel with more jobs available than tasks' '
 	test-tool run-command --ungroup run-command-parallel 5 sh -c "printf \"%s\n%s\n\" Hello World" >out 2>err &&
 	test_line_count = 8 out &&
@@ -145,6 +151,12 @@ test_expect_success 'run_command runs in parallel with as many jobs as tasks' '
 	test_cmp expect actual
 '
 
+test_expect_success 'run_command runs in parallel with as many jobs as tasks --pipe-output' '
+	test-tool run-command --pipe-output run-command-parallel 4 sh -c "printf \"%s\n%s\n\" Hello World" >out 2>err &&
+	test_must_be_empty out &&
+	test_line_count = 20 err
+'
+
 test_expect_success 'run_command runs ungrouped in parallel with as many jobs as tasks' '
 	test-tool run-command --ungroup run-command-parallel 4 sh -c "printf \"%s\n%s\n\" Hello World" >out 2>err &&
 	test_line_count = 8 out &&
@@ -156,6 +168,12 @@ test_expect_success 'run_command runs in parallel with more tasks than jobs avai
 	test_cmp expect actual
 '
 
+test_expect_success 'run_command runs in parallel with more tasks than jobs available --pipe-output' '
+	test-tool run-command --pipe-output run-command-parallel 3 sh -c "printf \"%s\n%s\n\" Hello World" >out 2>err &&
+	test_must_be_empty out &&
+	test_line_count = 20 err
+'
+
 test_expect_success 'run_command runs ungrouped in parallel with more tasks than jobs available' '
 	test-tool run-command --ungroup run-command-parallel 3 sh -c "printf \"%s\n%s\n\" Hello World" >out 2>err &&
 	test_line_count = 8 out &&
@@ -176,6 +194,12 @@ test_expect_success 'run_command is asked to abort gracefully' '
 	test_cmp expect actual
 '
 
+test_expect_success 'run_command is asked to abort gracefully --pipe-output' '
+	test-tool run-command --pipe-output run-command-abort 3 false >out 2>err &&
+	test_must_be_empty out &&
+	test_cmp expect err
+'
+
 test_expect_success 'run_command is asked to abort gracefully (ungroup)' '
 	test-tool run-command --ungroup run-command-abort 3 false >out 2>err &&
 	test_must_be_empty out &&
@@ -191,6 +215,12 @@ test_expect_success 'run_command outputs ' '
 	test_cmp expect actual
 '
 
+test_expect_success 'run_command outputs --pipe-output' '
+	test-tool run-command --pipe-output run-command-no-jobs 3 sh -c "printf \"%s\n%s\n\" Hello World" >out 2>err &&
+	test_must_be_empty out &&
+	test_cmp expect err
+'
+
 test_expect_success 'run_command outputs (ungroup) ' '
 	test-tool run-command --ungroup run-command-no-jobs 3 sh -c "printf \"%s\n%s\n\" Hello World" >out 2>err &&
 	test_must_be_empty out &&
-- 
2.38.0.135.g90850a2211-goog