Fix rewatch swallowing parse warnings (%todo)

CHANGELOG.md

@@ -19,11 +19,12 @@
 #### :rocket: New Feature
 
 - Add support for Set, Map, WeakSet and WeakMap to `@unboxed`. https://github.com/rescript-lang/rescript/pull/8009
-
 - Reanalyze: add reactive incremental analysis (`-reactive`, `-runs`, `-churn`) and Mermaid pipeline dumping (`-mermaid`). https://github.com/rescript-lang/rescript/pull/8092
 
 #### :bug: Bug fix
 
+- Fix rewatch swallowing parse warnings (%todo). https://github.com/rescript-lang/rescript/pull/8135
+
 #### :memo: Documentation
 
 #### :nail_care: Polish

rewatch/src/build.rs

@@ -261,9 +261,10 @@ pub fn incremental_build(
     let result_asts = parse::generate_asts(build_state, || pb.inc(1));
     let timing_ast_elapsed = timing_ast.elapsed();
 
-    match result_asts {
-        Ok(_ast) => {
+    let parse_warnings = match result_asts {
+        Ok(warnings) => {
             pb.finish();
+            warnings
         }
         Err(err) => {
             logs::finalize(&build_state.packages);
@@ -285,7 +286,7 @@ pub fn incremental_build(
                 plain_output,
             });
         }
-    }
+    };
     let deleted_modules = build_state.deleted_modules.clone();
     deps::get_deps(build_state, &deleted_modules);
     let timing_parse_total = timing_parse_start.elapsed();
@@ -304,6 +305,9 @@ pub fn incremental_build(
             );
         }
     }
+    if helpers::contains_ascii_characters(&parse_warnings) {
+        println!("{}", &parse_warnings);
+    }
 
     mark_modules_with_expired_deps_dirty(build_state);
     mark_modules_with_deleted_deps_dirty(&mut build_state.build_state);

tests/build_tests/build_warn_as_error/input.js

@@ -1,11 +1,14 @@
 import * as assert from "node:assert";
 import { setup } from "#dev/process";
 
-const { execBuildLegacy, execCleanLegacy } = setup(import.meta.dirname);
+const { execBuild, execClean } = setup(import.meta.dirname);
 
-const o1 = await execBuildLegacy();
+const o1 = await execBuild();
 
-const first_message = o1.stdout
+// biome-ignore lint/suspicious/noControlCharactersInRegex: strip ANSI color codes from output
+const stripAnsi = s => s.replace(/\x1b\[[0-9;]*m/g, "");
+
+const first_message = stripAnsi(o1.stdout)
   .split("\n")
   .map(s => s.trim())
   .find(s => s === "Warning number 110");
@@ -14,10 +17,10 @@ if (!first_message) {
   assert.fail(o1.stdout);
 }
 
-// Second build using -warn-error +110
-const o2 = await execBuildLegacy(["-warn-error", "+110"]);
+// Second build using --warn-error +110
+const o2 = await execBuild(["--warn-error", "+110"]);
 
-const second_message = o2.stdout
+const second_message = stripAnsi(o2.stdout)
   .split("\n")
   .map(s => s.trim())
   .find(s => s === "Warning number 110 (configured as error)");
@@ -26,17 +29,17 @@ if (!second_message) {
   assert.fail(o2.stdout);
 }
 
-// Third build, without -warn-error +110
+// Third build, without --warn-error +110
 // The result should not be a warning as error
-const o3 = await execBuildLegacy();
+const o3 = await execBuild();
 
-const third_message = o3.stdout
+const third_message = stripAnsi(o3.stdout)
   .split("\n")
   .map(s => s.trim())
-  .find(s => s === "Dependency Finished");
+  .find(s => s === "Warning number 110 (configured as error)");
 
-if (!third_message) {
+if (o3.status !== 0 || third_message) {
   assert.fail(o3.stdout);
 }
 
-await execCleanLegacy();
+await execClean();