Use actual TypeScript instead of @babel/preset-typescript.

index.js

@@ -90,8 +90,13 @@ function compile(source, options) {
   const optionsCopy = util.deepClone(options);
   const { ast, plugins, presets } = optionsCopy;
   delete optionsCopy.plugins;
+  delete optionsCopy.typescript;
   optionsCopy.ast = true;
 
+  if (options.typescript) {
+    precompileTypeScript(result, options);
+  }
+
   function transform(presets) {
     optionsCopy.plugins = [{
       parserOverride: parse
@@ -130,6 +135,36 @@ function compile(source, options) {
   return result;
 }
 
+function precompileTypeScript(result, options) {
+  const fileName = options.filename || options.sourceFileName;
+  if (fileName && ! fileName.endsWith(".ts") && ! fileName.endsWith(".tsx")) {
+    return;
+  }
+
+  const ts = require("typescript");
+  const tsResult = ts.transpileModule(result.code, {
+    fileName,
+    compilerOptions: {
+      target: ts.ScriptTarget.ES2018,
+      // Leave module syntax intact so that Babel/Reify can handle it.
+      module: ts.ModuleKind.ESNext,
+      sourceMap: true,
+      inlineSources: true,
+    }
+  });
+
+  result.code = tsResult.outputText.replace(
+    /\/\/# sourceMappingURL=.*?(\n|$)/g,
+    "$1" // preserve trailing \n characters
+  );
+
+  result.map = JSON.parse(tsResult.sourceMapText);
+  if (fileName) {
+    result.map.file = fileName;
+    result.map.sources = [fileName];
+  }
+}
+
 exports.minify = function minify(source, options) {
   // We are not compiling the code in this step, only minifying, so reify
   // is not used.

options.js

@@ -65,7 +65,6 @@ exports.getDefaults = function getDefaults(features) {
     }
 
     maybeAddReactPlugins(features, combined);
-    maybeAddTypeScriptPreset(features, combined.presets);
 
     if (features && features.jscript) {
       combined.plugins.push(
@@ -75,7 +74,7 @@ exports.getDefaults = function getDefaults(features) {
     }
   }
 
-  return finish([combined]);
+  return finish(features, [combined]);
 };
 
 function maybeAddReactPlugins(features, options) {
@@ -89,12 +88,6 @@ function maybeAddReactPlugins(features, options) {
   }
 }
 
-function maybeAddTypeScriptPreset(features, presets) {
-  if (features && features.typescript) {
-    presets.push(require("@babel/preset-typescript"));
-  }
-}
-
 function getDefaultsForModernBrowsers(features) {
   const combined = {
     presets: [],
@@ -111,17 +104,16 @@ function getDefaultsForModernBrowsers(features) {
     }
 
     maybeAddReactPlugins(features, combined);
-    maybeAddTypeScriptPreset(features, combined.presets);
   }
 
-  return finish([combined]);
+  return finish(features, [combined]);
 }
 
 const parserOpts = require("reify/lib/parsers/babel.js").options;
 const util = require("./util.js");
 
-function finish(presets) {
-  return {
+function finish(features, presets) {
+  const options = {
     compact: false,
     sourceMaps: false,
     ast: false,
@@ -132,6 +124,14 @@ function finish(presets) {
     parserOpts: util.deepClone(parserOpts),
     presets: presets
   };
+
+  if (features && features.typescript) {
+    // This additional option will be consumed by the meteorBabel.compile
+    // function before the options are passed to Babel.
+    options.typescript = true;
+  }
+
+  return options;
 }
 
 function isObject(value) {
@@ -191,10 +191,9 @@ function getDefaultsForNode8(features) {
 
   if (! compileModulesOnly) {
     maybeAddReactPlugins(features, combined);
-    maybeAddTypeScriptPreset(features, combined.presets);
   }
 
-  return finish([combined]);
+  return finish(features, [combined]);
 }
 
 exports.getMinifierDefaults = function getMinifierDefaults(features) {

package.json

@@ -36,7 +36,6 @@
     "@babel/plugin-transform-modules-commonjs": "^7.5.0",
     "@babel/plugin-transform-runtime": "^7.5.0",
     "@babel/preset-react": "^7.0.0",
-    "@babel/preset-typescript": "^7.3.3",
     "@babel/runtime": "^7.5.0",
     "@babel/template": "^7.4.4",
     "@babel/traverse": "^7.5.0",
@@ -46,7 +45,8 @@
     "convert-source-map": "^1.6.0",
     "lodash": "^4.17.11",
     "meteor-babel-helpers": "0.0.3",
-    "reify": "^0.20.12"
+    "reify": "^0.20.12",
+    "typescript": "^3.5.2"
   },
   "devDependencies": {
     "@babel/plugin-proposal-decorators": "7.4.4",

test/class-properties.ts

@@ -1,4 +1,7 @@
+const enum TestResult { PASS, FAIL }
+
 export class Test {
   public property: number = 1234;
+  public result = TestResult.PASS;
   constructor(public value: string) {}
 }

test/tests.js

@@ -288,9 +288,37 @@ describe("meteor-babel", () => {
     const tsTest = new Test("asdf");
     assert.strictEqual(tsTest.property, 1234);
     assert.strictEqual(tsTest.value, "asdf");
+    assert.strictEqual(typeof tsTest.result, "number");
     const jsTest = new (class { foo = 42 });
     assert.strictEqual(jsTest.foo, 42);
   });
+
+  it("can compile TypeScript syntax", () => {
+    const options = meteorBabel.getDefaultOptions({
+      typescript: true,
+    });
+
+    assert.strictEqual(options.typescript, true);
+
+    const result = meteorBabel.compile([
+      "export namespace Test {",
+      "  export const enabled = true;",
+      "}",
+    ].join("\n"), options);
+
+    assert.strictEqual(result.code, [
+      "module.export({",
+      "  Test: function () {",
+      "    return Test;",
+      "  }",
+      "});",
+      "var Test;",
+      "",
+      "(function (Test) {",
+      "  Test.enabled = true;",
+      "})(Test || module.runSetters(Test = {}));",
+    ].join("\n"));
+  });
 });
 
 describe("Babel", function() {