fix(cli): allow using file resource synchronously while being used async (#15747)

3 files changed, 219 insertions, 0 deletions

diff --git a/cli/tests/integration/run_tests.rs b/cli/tests/integration/run_tests.rs
index 20661f27f..118623760 100644
--- a/cli/tests/integration/run_tests.rs
+++ b/cli/tests/integration/run_tests.rs
@@ -18,6 +18,11 @@ itest!(stdin_read_all {
   input: Some("01234567890123456789012345678901234567890123456789"),
 });
 
+itest!(stdout_write_sync_async {
+  args: "run --quiet run/stdout_write_sync_async.ts",
+  output: "run/stdout_write_sync_async.out",
+});
+
 itest!(_001_hello {
   args: "run --reload 001_hello.js",
   output: "001_hello.js.out",
diff --git a/cli/tests/testdata/run/stdout_write_sync_async.out b/cli/tests/testdata/run/stdout_write_sync_async.out
new file mode 100644
index 000000000..91ebda1ca
--- /dev/null
+++ b/cli/tests/testdata/run/stdout_write_sync_async.out
@@ -0,0 +1,200 @@
+Hello
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diff --git a/cli/tests/testdata/run/stdout_write_sync_async.ts b/cli/tests/testdata/run/stdout_write_sync_async.ts
new file mode 100644
index 000000000..648999d8a
--- /dev/null
+++ b/cli/tests/testdata/run/stdout_write_sync_async.ts
@@ -0,0 +1,14 @@
+const encoder = new TextEncoder();
+const pending = [];
+
+for (let i = 0; i < 100; i++) {
+  // some code that will cause stdout to be written
+  // synchronously while the async write might be occurring
+  console.log("Hello");
+  pending.push(Deno.stdout.write(encoder.encode("Hello\n")));
+  if (i % 10) {
+    await new Promise((resolve) => setTimeout(resolve, 0));
+  }
+}
+
+await Promise.all(pending);