Fixes #41, handle declare keyword (#92)

* Fixes #41, handle declare keyword

* add comments to 'declare' tests

src/transform.js

@@ -640,6 +640,86 @@ const transform = {
     exit(path) {
       path.node.importKind = "value";
     }
+  },
+  DeclareVariable: {
+    exit(path) {
+      const { id } = path.node;
+
+      // TODO: patch @babel/types - t.variableDeclaration omits declare param
+      // const declaration = t.variableDeclaration("var", [
+      //   t.variableDeclarator(id),
+      // ], true),
+
+      path.replaceWith({
+        type: "VariableDeclaration",
+        kind: "var",
+        declarations: [t.variableDeclarator(id)],
+        declare: true
+      });
+    }
+  },
+  DeclareClass: {
+    exit(path) {
+      const { id, body, typeParameters } = path.node;
+      const superClass =
+        path.node.extends.length > 0 ? path.node.extends[0] : undefined;
+
+      // TODO: patch @babel/types - t.classDeclaration omits typescript params
+      // t.classDeclaration(id, superClass, body, [], false, true, [], undefined)
+
+      path.replaceWith({
+        type: "ClassDeclaration",
+        id,
+        typeParameters,
+        superClass,
+        superClassTypeParameters: superClass
+          ? superClass.typeParameters
+          : undefined,
+        body,
+        declare: true
+      });
+    }
+  },
+  DeclareFunction: {
+    exit(path) {
+      const { id } = path.node;
+      const { name, typeAnnotation } = id;
+
+      // TSFunctionType
+      const functionType = typeAnnotation.typeAnnotation;
+
+      // TODO: patch @babel/types - t.tsDeclaration only accepts 4 params but should accept 7
+      // t.tsDeclareFunction(
+      //   t.identifier(name),
+      //   t.noop(),
+      //   functionType.parameters,
+      //   functionType.typeAnnotation,
+      //   false, // async
+      //   true,
+      //   false, // generator
+      // ),
+
+      path.replaceWith({
+        type: "TSDeclareFunction",
+        id: t.identifier(name),
+        typeParameters: functionType.typeParameters,
+        params: functionType.parameters,
+        returnType: functionType.typeAnnotation,
+        declare: !t.isDeclareExportDeclaration(path.parent),
+        async: false, // TODO
+        generator: false // TODO
+      });
+    }
+  },
+  DeclareExportDeclaration: {
+    exit(path) {
+      const { declaration, default: _default } = path.node;
+
+      path.replaceWith({
+        type: _default ? "ExportDefaultDeclaration" : "ExportNamedDeclaration",
+        declaration
+      });
+    }
   }
 };
 

test/fixtures/convert/declare/declare-class/flow.js

@@ -0,0 +1,5 @@
+// @flow
+declare class Path<T> extends Node<U> {
+  // converts Path to a string
+  toString(): string;
+}

test/fixtures/convert/declare/declare-class/ts.js

@@ -0,0 +1,5 @@
+
+declare class Path<T> extends Node<U> {
+  // converts Path to a string
+  toString(): string;
+}

test/fixtures/convert/declare/declare-function/flow.js

@@ -0,0 +1,3 @@
+// @flow
+// Adds two numbers
+declare function foo(a: number, b: number): number;

test/fixtures/convert/declare/declare-function/ts.js

@@ -0,0 +1,3 @@
+
+// Adds two numbers
+declare function foo(a: number, b: number): number;

test/fixtures/convert/declare/declare-module/flow.js

@@ -0,0 +1,8 @@
+// @flow
+declare module "some-commonjs-module" {
+    // foo
+    declare export default function foo(): string;
+
+    // bar
+    declare export function bar(): boolean;
+}

test/fixtures/convert/declare/declare-module/ts.js

@@ -0,0 +1,8 @@
+
+declare module "some-commonjs-module" {
+  // foo
+  export default function foo(): string;
+
+  // bar
+  export function bar(): boolean;
+}

test/fixtures/convert/declare/declare-var/flow.js

@@ -0,0 +1,5 @@
+// @flow
+/**
+ * The constant PI ~ 3.141592
+ */
+declare var PI: number;

test/fixtures/convert/declare/declare-var/ts.js

@@ -0,0 +1,6 @@
+
+
+/**
+ * The constant PI ~ 3.141592
+ */
+declare var PI: number;