fix: Expand index types correctly (#369)

Author: thchia

src/utils/__tests__/getTSType-test.js

@@ -315,6 +315,38 @@ describe('getTSType', () => {
     });
   });
 
+  it('detects indexed access', () => {
+    const typePath = statement(`
+      var x: A["x"] = 2;
+
+      interface A { x: string };
+    `)
+      .get('declarations', 0)
+      .get('id')
+      .get('typeAnnotation')
+      .get('typeAnnotation');
+    expect(getTSType(typePath)).toEqual({
+      name: 'A["x"]',
+      raw: 'A["x"]',
+    });
+  });
+
+  it('resolves indexed access', () => {
+    const typePath = statement(`
+      var x: A["x"] = 2;
+
+      type A = { x: string };
+    `)
+      .get('declarations', 0)
+      .get('id')
+      .get('typeAnnotation')
+      .get('typeAnnotation');
+    expect(getTSType(typePath)).toEqual({
+      name: 'string',
+      raw: 'A["x"]',
+    });
+  });
+
   it('resolves types in scope', () => {
     const typePath = statement(`
       var x: MyType = 2;

src/utils/getTSType.js

@@ -19,6 +19,7 @@ import getTypeParameters, {
 import type {
   FlowElementsType,
   FlowFunctionArgumentType,
+  FlowLiteralType,
   FlowObjectSignatureType,
   FlowSimpleType,
   FlowTypeDescriptor,
@@ -54,6 +55,7 @@ const namedTypes = {
   TSTupleType: handleTSTupleType,
   TSTypeQuery: handleTSTypeQuery,
   TSTypeOperator: handleTSTypeOperator,
+  TSIndexedAccessType: handleTSIndexedAccessType,
 };
 
 function handleTSArrayType(
@@ -347,6 +349,40 @@ function handleTSTypeOperator(path: NodePath): ?FlowTypeDescriptor {
   }
 }
 
+function handleTSIndexedAccessType(
+  path: NodePath,
+  typeParams: ?TypeParameters,
+): FlowSimpleType {
+  // eslint-disable-next-line no-undef
+  const objectType: $Shape<FlowObjectSignatureType> = getTSTypeWithResolvedTypes(
+    path.get('objectType'),
+    typeParams,
+  );
+  // eslint-disable-next-line no-undef
+  const indexType: $Shape<FlowLiteralType> = getTSTypeWithResolvedTypes(
+    path.get('indexType'),
+    typeParams,
+  );
+
+  // We only get the signature if the objectType is a type (vs interface)
+  if (!objectType.signature)
+    return {
+      name: `${objectType.name}[${indexType.value.toString()}]`,
+      raw: printValue(path),
+    };
+  const resolvedType = objectType.signature.properties.find(p => {
+    // indexType.value = "'foo'"
+    return p.key === indexType.value.replace(/['"]+/g, '');
+  });
+  if (!resolvedType) {
+    return { name: 'unknown' };
+  }
+  return {
+    name: resolvedType.value.name,
+    raw: printValue(path),
+  };
+}
+
 let visitedTypes = {};
 
 function getTSTypeWithResolvedTypes(