fix(transform_react): downgrade nonfatal compiler diagnostics (#25418)

Expose nonfatal React Compiler diagnostics as warnings while preserving
fatal errors.

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napi/transform-react/README.md

@@ -34,9 +34,10 @@ if (result.fatal) {
 ```
 
 `errors` contains every diagnostic reported by parsing, the React Compiler, and
-the downstream transform. Some React Compiler bail-outs have error severity but
-are nonfatal under the default `panicThreshold`; check `fatal` to decide whether
-the transform emitted usable code.
+the downstream transform. Recoverable React Compiler bail-outs are warnings;
+compiler diagnostics retain error severity when `panicThreshold` makes the
+transform fatal. Check `fatal` to decide whether the transform emitted usable
+code.
 
 `reactCompiler` defaults to `true`. Set it to `false` to skip React Compiler,
 or pass an options object using the same names as

napi/transform-react/src/lib.rs

@@ -23,7 +23,7 @@ use napi_derive::napi;
 use oxc::{
     allocator::Allocator,
     codegen::{Codegen, CodegenOptions},
-    diagnostics::Diagnostics,
+    diagnostics::{Diagnostics, Severity},
     parser::Parser,
     semantic::{SemanticBuilder, SemanticBuilderReturn},
     transformer::Transformer,
@@ -98,13 +98,20 @@ fn transform_impl(
         return error_result(filename, source_text, diagnostics);
     }
 
-    let (react_output, react_diagnostics, react_fatal) = match react_compiler_options {
+    let (react_output, mut react_diagnostics, react_fatal) = match react_compiler_options {
         None => (None, Diagnostics::new(), false),
         Some(options) => match react_compiler_compile(&program, &semantic, &allocator, options) {
             CompileResult::Success { output, diagnostics } => (output, diagnostics, false),
             CompileResult::Fatal { diagnostics } => (None, diagnostics, true),
         },
     };
+    if !react_fatal {
+        for diagnostic in react_diagnostics.iter_mut() {
+            if diagnostic.severity == Severity::Error {
+                diagnostic.severity = Severity::Warning;
+            }
+        }
+    }
     diagnostics.extend(react_diagnostics);
     if react_fatal {
         return error_result(filename, source_text, diagnostics);

napi/transform-react/test/transform.test.ts

@@ -200,6 +200,7 @@ describe("transformSync", () => {
 
     expect(result.fatal).toBe(false);
     expect(result.errors).toHaveLength(1);
+    expect(result.errors[0].severity).toBe("Warning");
     expect(result.errors[0].message).toContain("[ReactCompiler] Suppression:");
     expect(result.code).not.toContain("react/compiler-runtime");
   });
@@ -224,7 +225,7 @@ describe("transformSync", () => {
     expect(result.fatal).toBe(false);
     expect(result.errors).toHaveLength(1);
     expect(result.errors[0]).toMatchObject({
-      severity: "Error",
+      severity: "Warning",
       message: expect.stringContaining("[ReactCompiler] Suppression:"),
     });
     expect(result.code).not.toBe("");
@@ -298,6 +299,7 @@ describe("transformSync", () => {
 
     expect(result.fatal).toBe(false);
     expect(result.errors).toHaveLength(1);
+    expect(result.errors[0].severity).toBe("Warning");
     expect(result.errors[0].message).toContain("[ReactCompiler] Suppression:");
     expect(result.code).toContain("react/compiler-runtime");
     expect(result.code).not.toContain("props: { text: string }");
@@ -327,6 +329,7 @@ describe("transformSync", () => {
       expect(result.fatal).toBe(true);
       expect(result.code).toBe("");
       expect(result.errors).toHaveLength(1);
+      expect(result.errors[0].severity).toBe("Error");
       expect(result.errors[0].message).toContain("[ReactCompiler] Suppression:");
     },
   );