feat(unstable): Add file locking APIs (#11746)

This commit adds following unstable APIs:
- Deno.flock()
- Deno.flockSync()
- Deno.funlock()
- Deno.funlockSync()

1 files changed, 102 insertions, 0 deletions

diff --git a/cli/tests/unit/flock_test.ts b/cli/tests/unit/flock_test.ts
new file mode 100644
index 000000000..13d09bcf5
--- /dev/null
+++ b/cli/tests/unit/flock_test.ts
@@ -0,0 +1,102 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+import { assertEquals, unitTest } from "./test_util.ts";
+
+unitTest(
+  { perms: { read: true, run: true, hrtime: true } },
+  async function flockFileSync() {
+    const path = "cli/tests/testdata/fixture.json";
+    const script = (exclusive: boolean, wait: number) => `
+          const { rid } = Deno.openSync("${path}");
+          Deno.flockSync(rid, ${exclusive ? "true" : "false"});
+          await new Promise(res => setTimeout(res, ${wait}));
+          Deno.funlockSync(rid);
+      `;
+    const run = (e: boolean, w: number) =>
+      Deno.run({ cmd: [Deno.execPath(), "eval", "--unstable", script(e, w)] });
+    const firstBlocksSecond = async (
+      first: boolean,
+      second: boolean,
+    ): Promise<boolean> => {
+      const firstPs = run(first, 1000);
+      await new Promise((res) => setTimeout(res, 250));
+      const start = performance.now();
+      const secondPs = run(second, 0);
+      await secondPs.status();
+      const didBlock = (performance.now() - start) > 500;
+      firstPs.close();
+      secondPs.close();
+      return didBlock;
+    };
+
+    assertEquals(
+      await firstBlocksSecond(true, false),
+      true,
+      "exclusive blocks shared",
+    );
+    assertEquals(
+      await firstBlocksSecond(false, true),
+      true,
+      "shared blocks exclusive",
+    );
+    assertEquals(
+      await firstBlocksSecond(true, true),
+      true,
+      "exclusive blocks exclusive",
+    );
+    assertEquals(
+      await firstBlocksSecond(false, false),
+      false,
+      "shared does not block shared",
+    );
+  },
+);
+
+unitTest(
+  { perms: { read: true, run: true, hrtime: true } },
+  async function flockFileAsync() {
+    const path = "cli/tests/testdata/fixture.json";
+    const script = (exclusive: boolean, wait: number) => `
+          const { rid } = await Deno.open("${path}");
+          await Deno.flock(rid, ${exclusive ? "true" : "false"});
+          await new Promise(res => setTimeout(res, ${wait}));
+          await Deno.funlock(rid);
+      `;
+    const run = (e: boolean, w: number) =>
+      Deno.run({ cmd: [Deno.execPath(), "eval", "--unstable", script(e, w)] });
+    const firstBlocksSecond = async (
+      first: boolean,
+      second: boolean,
+    ): Promise<boolean> => {
+      const firstPs = run(first, 1000);
+      await new Promise((res) => setTimeout(res, 250));
+      const start = performance.now();
+      const secondPs = run(second, 0);
+      await secondPs.status();
+      const didBlock = (performance.now() - start) > 500;
+      firstPs.close();
+      secondPs.close();
+      return didBlock;
+    };
+
+    assertEquals(
+      await firstBlocksSecond(true, false),
+      true,
+      "exclusive blocks shared",
+    );
+    assertEquals(
+      await firstBlocksSecond(false, true),
+      true,
+      "shared blocks exclusive",
+    );
+    assertEquals(
+      await firstBlocksSecond(true, true),
+      true,
+      "exclusive blocks exclusive",
+    );
+    assertEquals(
+      await firstBlocksSecond(false, false),
+      false,
+      "shared does not block shared",
+    );
+  },
+);