fix(toml): handle Infinity/NaN and Date in inline arrays

Inline array stringification used JSON.stringify, which silently turned
Infinity/-Infinity/NaN into 'null' and wrapped Date values in extra
quotes. Both forms broke round-trip through parse():

  stringify({x: [Infinity, -Infinity, NaN]}) // x = [null,null,null]
  stringify({x: [new Date(0)]})               // x = ["1970-01-01..."]

The same flaw affected #printAsInlineValue, which was the path for
mixed-type arrays — Date values were quoted and non-finite numbers
fell through as String(Infinity) / String(NaN).

Replace the JSON.stringify call in #arrayDeclaration with a per-element
walk through #printAsInlineValue, and teach #printAsInlineValue to emit
TOML's inf / -inf / nan keywords for non-finite numbers and to leave
Date values unquoted to match TOML's datetime literal syntax.

The 'handles mixed array' test pinned the buggy
date = "2022-05-13T00:00:00.000" form inside a nested inline map.
Updated to the correct unquoted form. Four new tests pin the issue's
specific repros (primitive Infinity/-Infinity/NaN, primitive Date,
mixed inf/nan/object, mixed date/object).

Fixes #7162 (partially — the null-in-array cases are left for a
follow-up since the spec disallows null in TOML and the right behavior
is a separate design call).

Author: LeSingh1

toml/stringify.ts

@@ -134,10 +134,19 @@ class Dumper {
   }
   #printAsInlineValue(value: unknown): string | number {
     if (value instanceof Date) {
-      return `"${this.#printDate(value)}"`;
+      // TOML datetime literals are unquoted (e.g. 1979-05-27T07:32:00Z).
+      // The previous wrapping in quotes caused the value to round-trip as a
+      // string instead of a Date (#7162).
+      return this.#printDate(value);
     } else if (typeof value === "string" || value instanceof RegExp) {
       return JSON.stringify(value.toString());
     } else if (typeof value === "number") {
+      // TOML uses inf / -inf / nan as the keywords for non-finite numbers
+      // (#7162). Letting String(Infinity) / String(NaN) leak produces
+      // tokens that don't reparse.
+      if (Number.isNaN(value)) return "nan";
+      if (value === Infinity) return "inf";
+      if (value === -Infinity) return "-inf";
       return value;
     } else if (typeof value === "boolean") {
       return value.toString();
@@ -185,7 +194,12 @@ class Dumper {
     return `${title} = `;
   }
   #arrayDeclaration(keys: string[], value: unknown[]): string {
-    return `${this.#declaration(keys)}${JSON.stringify(value)}`;
+    // JSON.stringify(value) turned Infinity / -Infinity / NaN into `null` and
+    // wrapped Date values in extra quotes, producing arrays that round-trip
+    // incorrectly (#7162). Use the per-element inline formatter instead so
+    // primitive arrays use the same TOML literal forms as mixed-type arrays.
+    const inline = value.map((x) => this.#printAsInlineValue(x)).join(",");
+    return `${this.#declaration(keys)}[${inline}]`;
   }
   #strDeclaration(keys: string[], value: string): string {
     return `${this.#declaration(keys)}${JSON.stringify(value)}`;

toml/stringify_test.ts

@@ -237,10 +237,12 @@ Deno.test({
         },
       },
     };
+    // TOML datetime literals are unquoted (see #7162). The previous
+    // `"2022-05-13T00:00:00.000"` form round-tripped as a string.
     const expected = `emptyArray = []
 mixedArray1 = [1,{b = 2}]
 mixedArray2 = [{b = 2},1]
-nestedArray1 = [[{b = 1,date = "2022-05-13T00:00:00.000"}]]
+nestedArray1 = [[{b = 1,date = 2022-05-13T00:00:00.000}]]
 nestedArray2 = [[[{b = 1}]]]
 nestedArray3 = [[],[{b = 1}]]
 
@@ -275,3 +277,46 @@ Deno.test({
     assertEquals(actual, expected);
   },
 });
+
+// https://github.com/denoland/std/issues/7162 — inline array stringification
+// used JSON.stringify, which turns Infinity/-Infinity/NaN into null and
+// wraps Date values in quotes. Both forms broke round-trip through parse().
+Deno.test({
+  name: "stringify() emits inf/-inf/nan in primitive arrays (#7162)",
+  fn() {
+    assertEquals(
+      stringify({ x: [Infinity, -Infinity, NaN] }),
+      "x = [inf,-inf,nan]\n",
+    );
+  },
+});
+
+Deno.test({
+  name: "stringify() emits inf/-inf/nan in mixed arrays (#7162)",
+  fn() {
+    assertEquals(
+      stringify({ x: [Infinity, -Infinity, NaN, {}] }),
+      "x = [inf,-inf,nan,{}]\n",
+    );
+  },
+});
+
+Deno.test({
+  name: "stringify() does not quote Date values in primitive arrays (#7162)",
+  fn() {
+    assertEquals(
+      stringify({ x: [new Date(0)] }),
+      "x = [1970-01-01T00:00:00.000]\n",
+    );
+  },
+});
+
+Deno.test({
+  name: "stringify() does not quote Date values in mixed arrays (#7162)",
+  fn() {
+    assertEquals(
+      stringify({ x: [new Date(0), {}] }),
+      "x = [1970-01-01T00:00:00.000,{}]\n",
+    );
+  },
+});