Comments + tests

Author: michaldudak

src/parsers/unionTypeResolver.ts

@@ -30,9 +30,19 @@ export function resolveUnionType(
 		memberTypes = type.origin.types;
 	}
 
+	// If there's no provided type node or it's is not a union,
+	// We check if the type declaration is an alias.
+	// If so, it can point to the original union type.
+	//
+	// For example:
+	// function f(x: Params) {}
+	// type Params = SomeType | SomeOtherType;
+	//
+	// In this case `typeNode` will be set to the type reference of the function parameter,
+	// so we extract the needed union definition.
 	const typeAliasDeclaration = type.aliasSymbol?.declarations?.[0];
-
 	if (
+		(!typeNode || !ts.isUnionTypeNode(typeNode)) &&
 		typeAliasDeclaration &&
 		ts.isTypeAliasDeclaration(typeAliasDeclaration) &&
 		ts.isUnionTypeNode(typeAliasDeclaration.type)

test/aliases-in-unions/input.ts

@@ -1,5 +1,9 @@
 export function f(x: Params) {}
 
+export interface Props {
+	x: Params;
+}
+
 type Params = Alias | 0;
 
 type SomeType = 1 | 2;

test/aliases-in-unions/output.json

@@ -51,6 +51,49 @@
 					}
 				]
 			}
+		},
+		{
+			"name": "Props",
+			"type": {
+				"kind": "object",
+				"typeName": {
+					"name": "Props"
+				},
+				"properties": [
+					{
+						"name": "x",
+						"type": {
+							"kind": "union",
+							"typeName": {
+								"name": "Params"
+							},
+							"types": [
+								{
+									"kind": "literal",
+									"value": 0
+								},
+								{
+									"kind": "union",
+									"typeName": {
+										"name": "Alias"
+									},
+									"types": [
+										{
+											"kind": "literal",
+											"value": 1
+										},
+										{
+											"kind": "literal",
+											"value": 2
+										}
+									]
+								}
+							]
+						},
+						"optional": false
+					}
+				]
+			}
 		}
 	]
 }