fix(runtime): support reading /proc using readFile (#12839)

3 files changed, 37 insertions, 12 deletions

diff --git a/cli/tests/unit/read_file_test.ts b/cli/tests/unit/read_file_test.ts
index 9b8f5e6df..90a6abc2c 100644
--- a/cli/tests/unit/read_file_test.ts
+++ b/cli/tests/unit/read_file_test.ts
@@ -105,15 +105,10 @@ unitTest(
 );
 
 unitTest(
-  { permissions: { read: true } },
-  async function readTextileWithAbortSignal() {
-    const ac = new AbortController();
-    queueMicrotask(() => ac.abort());
-    await assertRejects(async () => {
-      await Deno.readTextFile("cli/tests/testdata/fixture.json", {
-        signal: ac.signal,
-      });
-    });
+  { permissions: { read: true }, ignore: Deno.build.os !== "linux" },
+  async function readFileProcFs() {
+    const data = await Deno.readFile("/proc/self/stat");
+    assert(data.byteLength > 0);
   },
 );
 
diff --git a/cli/tests/unit/read_text_file_test.ts b/cli/tests/unit/read_text_file_test.ts
index 8a52831e0..1447fd028 100644
--- a/cli/tests/unit/read_text_file_test.ts
+++ b/cli/tests/unit/read_text_file_test.ts
@@ -83,3 +83,24 @@ unitTest(
     assertEquals(resourcesBefore, Deno.resources());
   },
 );
+
+unitTest(
+  { permissions: { read: true } },
+  async function readTextFileWithAbortSignal() {
+    const ac = new AbortController();
+    queueMicrotask(() => ac.abort());
+    await assertRejects(async () => {
+      await Deno.readFile("cli/tests/testdata/fixture.json", {
+        signal: ac.signal,
+      });
+    });
+  },
+);
+
+unitTest(
+  { permissions: { read: true }, ignore: Deno.build.os !== "linux" },
+  async function readTextFileProcFs() {
+    const data = await Deno.readTextFile("/proc/self/stat");
+    assert(data.length > 0);
+  },
+);
diff --git a/runtime/js/40_read_file.js b/runtime/js/40_read_file.js
index 53ac9b08a..5e90b523a 100644
--- a/runtime/js/40_read_file.js
+++ b/runtime/js/40_read_file.js
@@ -4,13 +4,18 @@
 ((window) => {
   const core = window.Deno.core;
   const { open, openSync } = window.__bootstrap.files;
-  const { readAllSyncSized, readAllInnerSized } = window.__bootstrap.io;
+  const { readAllSync, readAll, readAllSyncSized, readAllInnerSized } =
+    window.__bootstrap.io;
 
   function readFileSync(path) {
     const file = openSync(path);
     try {
       const { size } = file.statSync();
-      return readAllSyncSized(file, size);
+      if (size === 0) {
+        return readAllSync(file);
+      } else {
+        return readAllSyncSized(file, size);
+      }
     } finally {
       file.close();
     }
@@ -20,7 +25,11 @@
     const file = await open(path);
     try {
       const { size } = await file.stat();
-      return await readAllInnerSized(file, size, options);
+      if (size === 0) {
+        return await readAll(file);
+      } else {
+        return await readAllInnerSized(file, size, options);
+      }
     } finally {
       file.close();
     }