Improvements to bundling. (#3965)

Moves to using a minimal System loader for bundles generated by Deno.
TypeScript in 3.8 will be able to output TLA for modules, and the loader
is written to take advantage of that as soon as we update Deno to TS
3.8.

System also allows us to support `import.meta` and provide more ESM
aligned assignment of exports, as well as there is better handling of
circular imports.

The loader is also very terse versus to try to save overhead.

Also, fixed an issue where abstract classes were not being re-exported.

Fixes #2553
Fixes #3559
Fixes #3751
Fixes #3825
Refs #3301

4 files changed, 13 insertions, 12 deletions

diff --git a/cli/js/compiler_api_test.ts b/cli/js/compiler_api_test.ts
index 72b65ab5d..eef12c8cc 100644
--- a/cli/js/compiler_api_test.ts
+++ b/cli/js/compiler_api_test.ts
@@ -78,15 +78,15 @@ test(async function bundleApiSources() {
     "/bar.ts": `export const bar = "bar";\n`
   });
   assert(diagnostics == null);
-  assert(actual.includes(`instantiate("foo")`));
-  assert(actual.includes(`__rootExports["bar"]`));
+  assert(actual.includes(`__inst("foo")`));
+  assert(actual.includes(`__exp["bar"]`));
 });
 
 test(async function bundleApiNoSources() {
   const [diagnostics, actual] = await bundle("./cli/tests/subdir/mod1.ts");
   assert(diagnostics == null);
-  assert(actual.includes(`instantiate("mod1")`));
-  assert(actual.includes(`__rootExports["printHello3"]`));
+  assert(actual.includes(`__inst("mod1")`));
+  assert(actual.includes(`__exp["printHello3"]`));
 });
 
 test(async function bundleApiConfig() {
diff --git a/cli/js/compiler_bootstrap.ts b/cli/js/compiler_bootstrap.ts
index 585aec016..817486d12 100644
--- a/cli/js/compiler_bootstrap.ts
+++ b/cli/js/compiler_bootstrap.ts
@@ -55,4 +55,4 @@ export const TS_SNAPSHOT_PROGRAM = ts.createProgram({
  * We read all static assets during the snapshotting process, which is
  * why this is located in compiler_bootstrap.
  */
-export const BUNDLE_LOADER = getAsset("bundle_loader.js");
+export const SYSTEM_LOADER = getAsset("system_loader.js");
diff --git a/cli/js/compiler_bundler.ts b/cli/js/compiler_bundler.ts
index d334b0fc3..b9893620a 100644
--- a/cli/js/compiler_bundler.ts
+++ b/cli/js/compiler_bundler.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { BUNDLE_LOADER } from "./compiler_bootstrap.ts";
+import { SYSTEM_LOADER } from "./compiler_bootstrap.ts";
 import {
   assert,
   commonPath,
@@ -44,18 +44,18 @@ export function buildBundle(
     .replace(/\.\w+$/i, "");
   let instantiate: string;
   if (rootExports && rootExports.length) {
-    instantiate = `const __rootExports = instantiate("${rootName}");\n`;
+    instantiate = `const __exp = await __inst("${rootName}");\n`;
     for (const rootExport of rootExports) {
       if (rootExport === "default") {
-        instantiate += `export default __rootExports["${rootExport}"];\n`;
+        instantiate += `export default __exp["${rootExport}"];\n`;
       } else {
-        instantiate += `export const ${rootExport} = __rootExports["${rootExport}"];\n`;
+        instantiate += `export const ${rootExport} = __exp["${rootExport}"];\n`;
       }
     }
   } else {
-    instantiate = `instantiate("${rootName}");\n`;
+    instantiate = `await __inst("${rootName}");\n`;
   }
-  return `${BUNDLE_LOADER}\n${data}\n${instantiate}`;
+  return `${SYSTEM_LOADER}\n${data}\n${instantiate}`;
 }
 
 /** Set the rootExports which will by the `emitBundle()` */
@@ -80,6 +80,7 @@ export function setRootExports(program: ts.Program, rootModule: string): void {
     // out, so inspecting SymbolFlags that might be present that are type only
     .filter(
       sym =>
+        sym.flags & ts.SymbolFlags.Class ||
         !(
           sym.flags & ts.SymbolFlags.Interface ||
           sym.flags & ts.SymbolFlags.TypeLiteral ||
diff --git a/cli/js/compiler_host.ts b/cli/js/compiler_host.ts
index 291f6fbc5..0f6aa4d08 100644
--- a/cli/js/compiler_host.ts
+++ b/cli/js/compiler_host.ts
@@ -34,7 +34,7 @@ export const ASSETS = "$asset$";
  * runtime). */
 export const defaultBundlerOptions: ts.CompilerOptions = {
   inlineSourceMap: false,
-  module: ts.ModuleKind.AMD,
+  module: ts.ModuleKind.System,
   outDir: undefined,
   outFile: `${OUT_DIR}/bundle.js`,
   // disabled until we have effective way to modify source maps