fix(polyfill): correctly handle flag when its equal 0 (#20953)

Fixes https://github.com/denoland/deno/issues/20910

3 files changed, 4 insertions, 4 deletions

diff --git a/ext/node/polyfills/_fs/_fs_common.ts b/ext/node/polyfills/_fs/_fs_common.ts
index d1dfabc4f..3817ee9f8 100644
--- a/ext/node/polyfills/_fs/_fs_common.ts
+++ b/ext/node/polyfills/_fs/_fs_common.ts
@@ -108,7 +108,7 @@ export function checkEncoding(encoding: Encodings | null): Encodings | null {
 export function getOpenOptions(
   flag: string | number | undefined,
 ): Deno.OpenOptions {
-  if (!flag) {
+  if (flag === undefined) {
     return { create: true, append: true };
   }
 
diff --git a/ext/node/polyfills/_fs/_fs_open.ts b/ext/node/polyfills/_fs/_fs_open.ts
index 571a06a5d..fc5defb51 100644
--- a/ext/node/polyfills/_fs/_fs_open.ts
+++ b/ext/node/polyfills/_fs/_fs_open.ts
@@ -57,8 +57,8 @@ function convertFlagAndModeToOptions(
   flag?: openFlags,
   mode?: number,
 ): Deno.OpenOptions | undefined {
-  if (!flag && !mode) return undefined;
-  if (!flag && mode) return { mode };
+  if (flag === undefined && mode === undefined) return undefined;
+  if (flag === undefined && mode) return { mode };
   return { ...getOpenOptions(flag), mode };
 }
 
diff --git a/ext/node/polyfills/_fs/_fs_read.ts b/ext/node/polyfills/_fs/_fs_read.ts
index 6d7efbeef..66d5a4093 100644
--- a/ext/node/polyfills/_fs/_fs_read.ts
+++ b/ext/node/polyfills/_fs/_fs_read.ts
@@ -167,7 +167,7 @@ export function readSync(
   if (typeof offsetOrOpt === "number") {
     offset = offsetOrOpt;
     validateInteger(offset, "offset", 0);
-  } else {
+  } else if (offsetOrOpt !== undefined) {
     const opt = offsetOrOpt as readSyncOptions;
     offset = opt.offset ?? 0;
     length = opt.length ?? buffer.byteLength;