feat: add --compat flag to provide built-in Node modules (#12293)

This commit adds "--compat" flag. When the flag is passed a set of mappings for
built-in Node modules is injected into the import map. If user doesn't
explicitly provide an import map (using "--import-map" flag) then a map is
created on the fly. If there are already existing mappings in import map that
would clash with built-in Node modules a set of diagnostics is printed to the
terminal with suggestions how to proceed.

1 files changed, 14 insertions, 0 deletions

diff --git a/cli/tests/integration/compat_tests.rs b/cli/tests/integration/compat_tests.rs
new file mode 100644
index 000000000..4d93d370d
--- /dev/null
+++ b/cli/tests/integration/compat_tests.rs
@@ -0,0 +1,14 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+use crate::itest;
+
+itest!(fs_promises {
+  args: "run --compat --unstable -A compat/fs_promises.js",
+  output: "compat/fs_promises.out",
+});
+
+itest!(existing_import_map {
+  args: "run --compat --import-map compat/existing_import_map.json compat/fs_promises.js",
+  output: "compat/existing_import_map.out",
+  exit_code: 1,
+});