feature: add --stop-on-first-error CLI option

We expose a CLI option called --stop-on-first-error that exposes to the
user the internal behaviour of stopping the build on the first
encountered error.

- [x] option documentation
- [x] changelog
- [x] test

Signed-off-by: Ali Caglayan <alizter@gmail.com>

bin/common.ml

@@ -577,6 +577,7 @@ module Builder = struct
     ; cache_debug_flags : Dune_engine.Cache_debug_flags.t
     ; report_errors_config : Dune_engine.Report_errors_config.t
     ; separate_error_messages : bool
+    ; stop_on_first_error : bool
     ; require_dune_project_file : bool
     ; insignificant_changes : [ `React | `Ignore ]
     ; watch_exclusions : string list
@@ -952,6 +953,13 @@ module Builder = struct
         & info
             [ "display-separate-messages" ]
             ~doc:"Separate error messages with a blank line.")
+    and+ stop_on_first_error =
+      Arg.(
+        value
+        & flag
+        & info
+            [ "stop-on-first-error" ]
+            ~doc:"Stop the build as soon as the first error message is encountered.")
     in
     if Option.is_none stats_trace_file && stats_trace_extended
     then User_error.raise [ Pp.text "--trace-extended can only be used with --trace" ];
@@ -996,6 +1004,7 @@ module Builder = struct
     ; cache_debug_flags
     ; report_errors_config
     ; separate_error_messages
+    ; stop_on_first_error
     ; require_dune_project_file
     ; insignificant_changes = (if react_to_insignificant_changes then `React else `Ignore)
     ; watch_exclusions
@@ -1191,6 +1200,7 @@ let init ?action_runner ?log_file c =
   Dune_engine.Clflags.diff_command := c.builder.diff_command;
   Dune_engine.Clflags.promote := c.builder.promote;
   Dune_engine.Clflags.force := c.builder.force;
+  Dune_engine.Clflags.stop_on_first_error := c.builder.stop_on_first_error;
   Dune_rules.Clflags.store_orig_src_dir := c.builder.store_orig_src_dir;
   Dune_rules.Clflags.promote_install_files := c.builder.promote_install_files;
   Dune_engine.Clflags.always_show_command_line := c.builder.always_show_command_line;

doc/changes/8400.md

@@ -0,0 +1,2 @@
+- Add `--stop-on-first-error` option to `dune build` which will terminate the build when
+  the first error message is encountered. (#8400, @pmwhite and @Alizter)

test/blackbox-tests/test-cases/stop-on-first-error.t/bar.ml

@@ -0,0 +1 @@
+let run = syntax error

test/blackbox-tests/test-cases/stop-on-first-error.t/baz.ml

@@ -0,0 +1 @@
+let run = syntax error

test/blackbox-tests/test-cases/stop-on-first-error.t/dune

@@ -0,0 +1,3 @@
+(executable
+ (name foo)
+ (modules foo bar baz))

test/blackbox-tests/test-cases/stop-on-first-error.t/dune-project

@@ -0,0 +1 @@
+(lang dune 3.10)

test/blackbox-tests/test-cases/stop-on-first-error.t/foo.ml

@@ -0,0 +1,3 @@
+let () =
+  Bar.run ();
+  Baz.run ()

test/blackbox-tests/test-cases/stop-on-first-error.t/run.t

@@ -0,0 +1,19 @@
+Here we demonstrate the --stop-on-first-error behaviour.
+
+  $ dune build
+  File "bar.ml", line 1, characters 10-16:
+  1 | let run = syntax error
+                ^^^^^^
+  Error: Unbound value syntax
+  File "baz.ml", line 1, characters 10-16:
+  1 | let run = syntax error
+                ^^^^^^
+  Error: Unbound value syntax
+  [1]
+
+  $ dune build --stop-on-first-error
+  File "bar.ml", line 1, characters 10-16:
+  1 | let run = syntax error
+                ^^^^^^
+  Error: Unbound value syntax
+  [1]