feat(unstable): Node CJS and ESM resolvers for compat mode (#12424)

This commit adds CJS and ESM Node resolvers to the "--compat" mode.

The functionality is spread across "cli/compat" module and Node compatibility
layer in "deno_std/node"; this stems from the fact that ES module resolution
can only be implemented in Rust as it needs to directly integrated with 
"deno_core"; however "deno_std/node" already provided CJS module resolution.

Currently this resolution is only active when running a files using 
"deno run --compat --unstable <filename>", and is not available in other
subcommands, which will be changed in follow up commits.

1 files changed, 19 insertions, 29 deletions

diff --git a/cli/proc_state.rs b/cli/proc_state.rs
index e45e7c539..461599fc4 100644
--- a/cli/proc_state.rs
+++ b/cli/proc_state.rs
@@ -3,6 +3,7 @@
 use crate::cache;
 use crate::colors;
 use crate::compat;
+use crate::compat::NodeEsmResolver;
 use crate::config_file::ConfigFile;
 use crate::deno_dir;
 use crate::emit;
@@ -195,7 +196,7 @@ impl ProcState {
         None
       };
 
-    let mut maybe_import_map: Option<ImportMap> =
+    let maybe_import_map: Option<ImportMap> =
       match flags.import_map_path.as_ref() {
         None => None,
         Some(import_map_url) => {
@@ -217,32 +218,6 @@ impl ProcState {
         }
       };
 
-    if flags.compat {
-      let mut import_map = match maybe_import_map {
-        Some(import_map) => import_map,
-        None => {
-          // INFO: we're creating an empty import map, with its specifier pointing
-          // to `CWD/node_import_map.json` to make sure the map still works as expected.
-          let import_map_specifier =
-            std::env::current_dir()?.join("node_import_map.json");
-          ImportMap::from_json(import_map_specifier.to_str().unwrap(), "{}")
-            .unwrap()
-        }
-      };
-      let node_builtins = compat::get_mapped_node_builtins();
-      let diagnostics = import_map.update_imports(node_builtins)?;
-
-      if !diagnostics.is_empty() {
-        log::info!("Some Node built-ins were not added to the import map:");
-        for diagnostic in diagnostics {
-          log::info!("  - {}", diagnostic);
-        }
-        log::info!("If you want to use Node built-ins provided by Deno remove listed specifiers from \"imports\" mapping in the import map file.");
-      }
-
-      maybe_import_map = Some(import_map);
-    }
-
     let maybe_inspect_host = flags.inspect.or(flags.inspect_brk);
     let maybe_inspector_server = maybe_inspect_host.map(|host| {
       Arc::new(InspectorServer::new(host, version::get_user_agent()))
@@ -316,14 +291,29 @@ impl ProcState {
     );
     let maybe_locker = as_maybe_locker(self.lockfile.clone());
     let maybe_imports = self.get_maybe_imports();
-    let maybe_resolver =
+    let node_resolver = NodeEsmResolver;
+    let import_map_resolver =
       self.maybe_import_map.as_ref().map(ImportMapResolver::new);
+    let maybe_resolver = if self.flags.compat {
+      Some(node_resolver.as_resolver())
+    } else {
+      import_map_resolver.as_ref().map(|im| im.as_resolver())
+    };
+    // TODO(bartlomieju): this is very make-shift, is there an existing API
+    // that we could include it like with "maybe_imports"?
+    let roots = if self.flags.compat {
+      let mut r = vec![compat::GLOBAL_URL.clone()];
+      r.extend(roots);
+      r
+    } else {
+      roots
+    };
     let graph = deno_graph::create_graph(
       roots,
       is_dynamic,
       maybe_imports,
       &mut cache,
-      maybe_resolver.as_ref().map(|im| im.as_resolver()),
+      maybe_resolver,
       maybe_locker,
       None,
     )