From d9b130410b78face988e2fa5c3939e3584bc02f7 Mon Sep 17 00:00:00 2001
From: VishnuJin <45007338+VishnuJin@users.noreply.github.com>
Date: Tue, 4 Jan 2022 00:40:17 +0530
Subject: feat(compat) preload Node.js built-in modules in global vars REPL
 (#13127)

This commit adds preloading of built-in Node.js modules in
the REPL if running with "deno repl --compat --unstable".
---
 cli/compat/mod.rs                     | 15 +++++++++++++++
 cli/main.rs                           |  2 ++
 cli/tests/integration/compat_tests.rs | 12 ++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/cli/compat/mod.rs b/cli/compat/mod.rs
index 4ed02dfe7..401e1ab40 100644
--- a/cli/compat/mod.rs
+++ b/cli/compat/mod.rs
@@ -140,3 +140,18 @@ pub(crate) fn add_global_require(
 fn escape_for_single_quote_string(text: &str) -> String {
   text.replace(r"\", r"\\").replace("'", r"\'")
 }
+
+pub fn setup_builtin_modules(
+  js_runtime: &mut JsRuntime,
+) -> Result<(), AnyError> {
+  let mut script = String::new();
+  for module in SUPPORTED_MODULES {
+    // skipping the modules that contains '/' as they are not available in NodeJS repl as well
+    if !module.contains('/') {
+      script = format!("{}const {} = require('{}');\n", script, module, module);
+    }
+  }
+
+  js_runtime.execute_script("setup_node_builtins.js", &script)?;
+  Ok(())
+}
diff --git a/cli/main.rs b/cli/main.rs
index 53069a796..5fe5d6659 100644
--- a/cli/main.rs
+++ b/cli/main.rs
@@ -902,6 +902,8 @@ async fn repl_command(
   if flags.compat {
     worker.execute_side_module(&compat::GLOBAL_URL).await?;
     compat::add_global_require(&mut worker.js_runtime, main_module.as_str())?;
+    worker.run_event_loop(false).await?;
+    compat::setup_builtin_modules(&mut worker.js_runtime)?;
   }
   worker.run_event_loop(false).await?;
 
diff --git a/cli/tests/integration/compat_tests.rs b/cli/tests/integration/compat_tests.rs
index 714329dc2..7eff64f12 100644
--- a/cli/tests/integration/compat_tests.rs
+++ b/cli/tests/integration/compat_tests.rs
@@ -132,3 +132,15 @@ fn node_compat_url() {
   assert!(!err.is_empty());
   assert!(err.contains("file:///non_existent/node/global.ts"));
 }
+
+#[test]
+fn native_modules_as_global_vars() {
+  let (out, _err) = util::run_and_collect_output_with_args(
+    true,
+    vec!["repl", "--compat", "--unstable", "--quiet"],
+    Some(vec!["if(cluster && v8 && sys) { true } else { false }"]),
+    None,
+    false,
+  );
+  assert!(out.contains("true"));
+}
-- 
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