Merge pull request #26639 from storybookjs/kasper/empty-union

React-Docgen: Make sure to be able to handle empty unions
(cherry picked from commit 889cfdf)

code/lib/docs-tools/src/argTypes/convert/flow/convert.ts

@@ -41,13 +41,13 @@ export const convert = (type: FlowType): SBType | void => {
     case 'signature':
       return { ...base, ...convertSig(type) };
     case 'union':
-      if (type.elements.every(isLiteral)) {
-        return { ...base, name: 'enum', value: type.elements.map(toEnumOption) };
+      if (type.elements?.every(isLiteral)) {
+        return { ...base, name: 'enum', value: type.elements?.map(toEnumOption) };
       }
-      return { ...base, name, value: type.elements.map(convert) };
+      return { ...base, name, value: type.elements?.map(convert) };
 
     case 'intersection':
-      return { ...base, name, value: type.elements.map(convert) };
+      return { ...base, name, value: type.elements?.map(convert) };
     default:
       return { ...base, name: 'other', value: name };
   }

code/lib/docs-tools/src/argTypes/convert/typescript/convert.ts

@@ -38,19 +38,19 @@ export const convert = (type: TSType): SBType | void => {
       return { ...base, ...convertSig(type) };
     case 'union':
       let result;
-      if (type.elements.every((element) => element.name === 'literal')) {
+      if (type.elements?.every((element) => element.name === 'literal')) {
         result = {
           ...base,
           name: 'enum',
           // @ts-expect-error fix types
-          value: type.elements.map((v) => parseLiteral(v.value)),
+          value: type.elements?.map((v) => parseLiteral(v.value)),
         };
       } else {
-        result = { ...base, name, value: type.elements.map(convert) };
+        result = { ...base, name, value: type.elements?.map(convert) };
       }
       return result;
     case 'intersection':
-      return { ...base, name, value: type.elements.map(convert) };
+      return { ...base, name, value: type.elements?.map(convert) };
     default:
       return { ...base, name: 'other', value: name };
   }

code/lib/docs-tools/src/argTypes/convert/typescript/types.ts

@@ -9,7 +9,7 @@ type TSArgType = TSType;
 
 type TSCombinationType = TSBaseType & {
   name: 'union' | 'intersection';
-  elements: TSType[];
+  elements?: TSType[];
 };
 
 type TSFuncSigType = TSBaseType & {