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, 60 insertions, 0 deletions

diff --git a/cli/compat.rs b/cli/compat.rs
new file mode 100644
index 000000000..a3d16538d
--- /dev/null
+++ b/cli/compat.rs
@@ -0,0 +1,60 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+use std::collections::HashMap;
+
+static SUPPORTED_MODULES: &[&str] = &[
+  "assert",
+  "assert/strict",
+  "async_hooks",
+  "buffer",
+  "child_process",
+  "cluster",
+  "console",
+  "constants",
+  "crypto",
+  "dgram",
+  "dns",
+  "domain",
+  "events",
+  "fs",
+  "fs/promises",
+  "http",
+  "https",
+  "module",
+  "net",
+  "os",
+  "path",
+  "path/posix",
+  "path/win32",
+  "perf_hooks",
+  "process",
+  "querystring",
+  "readline",
+  "stream",
+  "stream/promises",
+  "stream/web",
+  "string_decoder",
+  "sys",
+  "timers",
+  "timers/promises",
+  "tls",
+  "tty",
+  "url",
+  "util",
+  "util/types",
+  "v8",
+  "vm",
+  "zlib",
+];
+
+pub fn get_mapped_node_builtins() -> HashMap<String, String> {
+  let mut mappings = HashMap::new();
+
+  for module in SUPPORTED_MODULES {
+    // TODO(bartlomieju): this is unversioned, and should be fixed to use latest stable?
+    let module_url = format!("https://deno.land/std/node/{}.ts", module);
+    mappings.insert(module.to_string(), module_url);
+  }
+
+  mappings
+}