React: Preserve discriminated union prop values in metadata extraction

code/renderers/react/src/componentManifest/componentMeta/componentMetaExtractor.props.test.ts

@@ -360,6 +360,40 @@ describe('prop extraction', () => {
         },
       });
     });
+
+    it('merges same-named prop types across union members', async () => {
+      const entry = await extract(
+        'Component',
+        dedent`
+          import React from 'react';
+          interface BaseProps { variant?: 'a' | 'b' }
+          interface VariantAProps extends BaseProps {
+            variant?: 'a';
+            valueA?: string;
+            valueB?: never;
+          }
+          interface VariantBProps extends BaseProps {
+            variant: 'b';
+            valueA?: never;
+            valueB: string;
+          }
+          type Props = VariantAProps | VariantBProps;
+          export const Component: React.FC<Props> = (props) => <div />;
+        `
+      );
+
+      expect(entry.component?.reactComponentMeta).toMatchObject({
+        props: {
+          variant: {
+            required: false,
+            type: {
+              name: 'enum',
+              value: [{ value: '"a"' }, { value: '"b"' }],
+            },
+          },
+        },
+      });
+    });
   });
 
   describe('utility types', () => {

code/renderers/react/src/componentManifest/componentMeta/componentMetaExtractor.ts

@@ -1255,12 +1255,14 @@ function extractPropItem(
   checker: ts.TypeChecker,
   prop: ts.Symbol,
   contextNode: ts.Node,
-  defaultsMap?: Map<string, string>
+  defaultsMap?: Map<string, string>,
+  typeOverride?: ts.Type
 ): PropItem {
   const isOptional = !!(prop.flags & typescript.SymbolFlags.Optional);
   const isRequired = !isOptional;
 
-  const propType = checker.getTypeOfSymbolAtLocation(prop, contextNode);
+  // Union props keep one member's metadata but need the merged type.
+  const propType = typeOverride ?? checker.getTypeOfSymbolAtLocation(prop, contextNode);
   const type = serializeType(typescript, checker, propType, isRequired);
 
   const description = typescript.displayPartsToString(prop.getDocumentationComment(checker));
@@ -1530,7 +1532,20 @@ export function serializeComponentDoc(
     if (excluded.has(prop.getName())) {
       continue;
     }
-    const item = extractPropItem(typescript, checker, prop, contextNode, defaultsMap);
+    const unionProp = isUnionType(propsType)
+      ? checker.getPropertyOfType(propsType, prop.getName())
+      : undefined;
+    const unionPropType = unionProp
+      ? checker.getTypeOfSymbolAtLocation(unionProp, contextNode)
+      : undefined;
+    const item = extractPropItem(
+      typescript,
+      checker,
+      prop,
+      contextNode,
+      defaultsMap,
+      unionPropType
+    );
     if (unionForceOptional?.has(prop.getName())) {
       item.required = false;
     }