Adding createFlowUnionType in place of createUnionTypeAnnotation without breaking change

packages/babel-traverse/src/path/inference/inferer-reference.js

@@ -99,6 +99,10 @@ function getTypeAnnotationBindingConstantViolations(binding, path, name) {
     return t.createTSUnionType(types);
   }
 
+  if (t.createFlowUnionType) {
+    return t.createFlowUnionType(types);
+  }
+
   return t.createUnionTypeAnnotation(types);
 }
 
@@ -214,6 +218,13 @@ function getConditionalAnnotation(binding, path, name) {
       };
     }
 
+    if (t.createFlowUnionType) {
+      return {
+        typeAnnotation: t.createFlowUnionType(types),
+        ifStatement,
+      };
+    }
+
     return {
       typeAnnotation: t.createUnionTypeAnnotation(types),
       ifStatement,

packages/babel-traverse/src/path/inference/inferers.js

@@ -92,6 +92,10 @@ export function LogicalExpression() {
     return t.createTSUnionType(argumentTypes);
   }
 
+  if (t.createFlowUnionType) {
+    return t.createFlowUnionType(argumentTypes);
+  }
+
   return t.createUnionTypeAnnotation(argumentTypes);
 }
 
@@ -105,6 +109,10 @@ export function ConditionalExpression() {
     return t.createTSUnionType(argumentTypes);
   }
 
+  if (t.createFlowUnionType) {
+    return t.createFlowUnionType(argumentTypes);
+  }
+
   return t.createUnionTypeAnnotation(argumentTypes);
 }
 

packages/babel-types/scripts/generators/flow.js

@@ -128,6 +128,8 @@ lines.push(
   `declare function createTypeAnnotationBasedOnTypeof(type: 'string' | 'number' | 'undefined' | 'boolean' | 'function' | 'object' | 'symbol'): ${NODE_PREFIX}TypeAnnotation`,
   // eslint-disable-next-line max-len
   `declare function createUnionTypeAnnotation(types: Array<${NODE_PREFIX}FlowType>): ${NODE_PREFIX}UnionTypeAnnotation`,
+  // eslint-disable-next-line max-len
+  `declare function createFlowUnionType(types: Array<${NODE_PREFIX}FlowType>): ${NODE_PREFIX}UnionTypeAnnotation`,
   // this smells like "internal API"
   // eslint-disable-next-line max-len
   `declare function buildChildren(node: { children: Array<${NODE_PREFIX}JSXText | ${NODE_PREFIX}JSXExpressionContainer | ${NODE_PREFIX}JSXSpreadChild | ${NODE_PREFIX}JSXElement | ${NODE_PREFIX}JSXFragment | ${NODE_PREFIX}JSXEmptyExpression> }): Array<${NODE_PREFIX}JSXText | ${NODE_PREFIX}JSXExpressionContainer | ${NODE_PREFIX}JSXSpreadChild | ${NODE_PREFIX}JSXElement | ${NODE_PREFIX}JSXFragment>`,

packages/babel-types/scripts/generators/typescript.js

@@ -144,9 +144,11 @@ lines.push(
   // eslint-disable-next-line max-len
   `export function createTypeAnnotationBasedOnTypeof(type: 'string' | 'number' | 'undefined' | 'boolean' | 'function' | 'object' | 'symbol'): StringTypeAnnotation | VoidTypeAnnotation | NumberTypeAnnotation | BooleanTypeAnnotation | GenericTypeAnnotation`,
   `export function createUnionTypeAnnotation<T extends FlowType>(types: [T]): T`,
+  `export function createFlowUnionType<T extends FlowType>(types: [T]): T`,
   // this probably misbehaves if there are 0 elements, and it's not a UnionTypeAnnotation if there's only 1
   // it is possible to require "2 or more" for this overload ([T, T, ...T[]]) but it requires typescript 3.0
   `export function createUnionTypeAnnotation(types: ReadonlyArray<FlowType>): UnionTypeAnnotation`,
+  `export function createFlowUnionType(types: ReadonlyArray<FlowType>): UnionTypeAnnotation`,
   // this smells like "internal API"
   // eslint-disable-next-line max-len
   `export function buildChildren(node: { children: ReadonlyArray<JSXText | JSXExpressionContainer | JSXSpreadChild | JSXElement | JSXFragment | JSXEmptyExpression> }): JSXElement['children']`,

packages/babel-types/src/builders/flow/createUnionTypeAnnotation.js → packages/babel-types/src/builders/flow/createFlowUnionType.js

@@ -6,9 +6,7 @@ import removeTypeDuplicates from "../../modifications/flow/removeTypeDuplicates"
  * Takes an array of `types` and flattens them, removing duplicates and
  * returns a `UnionTypeAnnotation` node containg them.
  */
-export default function createUnionTypeAnnotation(
-  types: Array<Object>,
-): Object {
+export default function createFlowUnionType(types: Array<Object>): Object {
   const flattened = removeTypeDuplicates(types);
 
   if (flattened.length === 1) {

packages/babel-types/src/index.js

@@ -9,7 +9,8 @@ export * from "./asserts/generated";
 
 // builders
 export { default as createTypeAnnotationBasedOnTypeof } from "./builders/flow/createTypeAnnotationBasedOnTypeof";
-export { default as createUnionTypeAnnotation } from "./builders/flow/createUnionTypeAnnotation";
+export { default as createUnionTypeAnnotation } from "./builders/flow/createFlowUnionType";
+export { default as createFlowUnionType } from "./builders/flow/createFlowUnionType";
 export { default as createTSUnionType } from "./builders/typescript/createTSUnionType";
 export * from "./builders/generated";