From a02794904ab97096a76100d07dc28c6d787dbbcc Mon Sep 17 00:00:00 2001
From: robobun <117481402+robobun@users.noreply.github.com>
Date: Wed, 4 Nov 2026 03:54:55 +0000
Subject: [PATCH] dev server console: print each key of an array that is not an
 array index

The browser console formatter listed the named keys of an array with a
test on Number(key). A key such as "1.5", "01" or "" passed that test
when the array was long enough, so the formatter printed it neither as
an element nor as a named key.

Test each own key against the canonical form of an array index. Write
the label of a named key through formatPropertyKey, as formatPlainObject
does, so that a restored key such as "" prints as a quoted string.
---
 src/runtime/bake/client/inspect.ts | 17 ++++----
 test/bake/dev/esm.test.ts          | 66 ++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 8 deletions(-)

diff --git a/src/runtime/bake/client/inspect.ts b/src/runtime/bake/client/inspect.ts
index 522725bb6da8..388036dc5aef 100644
--- a/src/runtime/bake/client/inspect.ts
+++ b/src/runtime/bake/client/inspect.ts
@@ -247,6 +247,9 @@ function formatObject(ctx: InspectContext, value: any, recurseTimes: number) {
   return output;
 }
 
+// Hoisted so that the test of each own key in formatArray allocates nothing.
+const arrayIndexKey = /^(?:0|[1-9]\d*)$/;
+
 /**
  * Format an array
  * @param {Object} ctx - Context object
@@ -275,14 +278,12 @@ function formatArray(ctx: InspectContext, value: any[], recurseTimes: number) {
   }
 
   // Add array properties that aren't indices
-  const keys = Object.keys(value).filter(key => {
-    return !(Number(key) >= 0 && Number(key) < value.length && Number(key) === +key);
-  });
-
-  if (keys.length > 0) {
-    for (const key of keys) {
-      output.push(`${key}: ${formatValue(ctx, value[key], recurseTimes)}`);
-    }
+  const length = value.length;
+  const keys = Object.keys(value);
+  for (let i = 0; i < keys.length; i++) {
+    const key = keys[i];
+    if (arrayIndexKey.test(key) && +key < length) continue;
+    output.push(`${formatPropertyKey(key)}: ${formatValue(ctx, value[key], recurseTimes)}`);
   }
 
   return `[ ${output.join(", ")} ]`;
diff --git a/test/bake/dev/esm.test.ts b/test/bake/dev/esm.test.ts
index 82f69cf6f377..82090a5aaeb0 100644
--- a/test/bake/dev/esm.test.ts
+++ b/test/bake/dev/esm.test.ts
@@ -466,6 +466,72 @@ devTest("browser field is used", {
   },
 });
 
+devTest("browser console forwarding prints a key of an array that is not an array index", {
+  files: {
+    "index.html": emptyHtmlFile({
+      scripts: ["index.ts"],
+    }),
+    "index.ts": `
+      const mid = [1, 2, 3];
+      mid[mid.length / 2] = "mid";
+      const numeric = { "": 1, "01": 2, "1.5": 3 };
+      console.log("drop-probe", mid, Object.assign([5, 6], numeric), numeric);
+      console.log("length-probe", Object.assign([5], { "1.5": 1, "01": 2 }));
+      console.log("range-probe", Object.assign([5], { "4294967295": "far", "-1": -1 }));
+      const long = new Array(150).fill(0);
+      long["120.5"] = "a";
+      long["099"] = "b";
+      console.log("long-probe", long);
+      console.log("nested-probe", { list: Object.assign([5, 6], { "1.5": 1 }) });
+      console.log("newline-probe", Object.assign([5], { "\\n": 1 }));
+      console.log("hole-probe", Object.assign([1, , , 4], { "01": 1, "1.5": 2 }));
+      console.log("label-probe", Object.assign([5], { "a b": 1, ok: 2 }), "xabcx".match(/abc/));
+    `,
+    "bun.app.ts": `
+      import html from "./index.html";
+      export default {
+        static: {
+          "/": html,
+        },
+        development: {
+          console: true,
+        },
+        fetch(req) {
+          return new Response("Not Found", { status: 404 });
+        },
+      };
+    `,
+  },
+  htmlFiles: [],
+  async test(dev) {
+    await using c = await dev.client("/");
+    await c.expectMessage(
+      "drop-probe",
+      "length-probe",
+      "range-probe",
+      "long-probe",
+      "nested-probe",
+      "newline-probe",
+      "hole-probe",
+      "label-probe",
+    );
+    await dev.output.waitForLine(/\[browser\].*label-probe/);
+    const forwarded = dev.output.lines.filter(line => line.includes("[browser]")).map(line => Bun.stripANSI(line));
+    expect(forwarded).toEqual([
+      "[browser] drop-probe [ 1, 2, 3, '1.5': 'mid' ] [ 5, 6, '': 1, '01': 2, '1.5': 3 ] { '': 1, '01': 2, '1.5': 3 }",
+      "[browser] length-probe [ 5, '1.5': 1, '01': 2 ]",
+      "[browser] range-probe [ 5, '4294967295': 'far', '-1': -1 ]",
+      // The first 100 elements, then the rest as a count, then the named keys.
+      `[browser] long-probe [ ${Buffer.alloc(300, "0, ").toString()}... 50 more items, '120.5': 'a', '099': 'b' ]`,
+      "[browser] nested-probe { list: [ 5, 6, '1.5': 1 ] }",
+      "[browser] newline-probe [ 5, '\\n': 1 ]",
+      // Two holes and two named keys: the array has as many own keys as elements.
+      "[browser] hole-probe [ 1, empty, empty, 4, '01': 1, '1.5': 2 ]",
+      "[browser] label-probe [ 5, 'a b': 1, ok: 2 ] [ 'abc', index: 1, input: 'xabcx', groups: undefined ]",
+    ]);
+  },
+});
+
 devTest("browser console forwarding strips terminal control bytes", {
   files: {
     "index.html": emptyHtmlFile({