fix: harden format time fallback handling

src/infra/format-time/format-datetime.ts

@@ -59,36 +59,40 @@ export function formatZonedTimestamp(
   date: Date,
   options?: FormatZonedTimestampOptions,
 ): string | undefined {
-  const intlOptions: Intl.DateTimeFormatOptions = {
-    timeZone: options?.timeZone,
-    year: "numeric",
-    month: "2-digit",
-    day: "2-digit",
-    hour: "2-digit",
-    minute: "2-digit",
-    hourCycle: "h23",
-    timeZoneName: "short",
-  };
-  if (options?.displaySeconds) {
-    intlOptions.second = "2-digit";
-  }
-  const parts = new Intl.DateTimeFormat("en-US", intlOptions).formatToParts(date);
-  const pick = (type: string) => parts.find((part) => part.type === type)?.value;
-  const yyyy = pick("year");
-  const mm = pick("month");
-  const dd = pick("day");
-  const hh = pick("hour");
-  const min = pick("minute");
-  const sec = options?.displaySeconds ? pick("second") : undefined;
-  const tz = [...parts]
-    .toReversed()
-    .find((part) => part.type === "timeZoneName")
-    ?.value?.trim();
-  if (!yyyy || !mm || !dd || !hh || !min) {
+  try {
+    const intlOptions: Intl.DateTimeFormatOptions = {
+      timeZone: options?.timeZone,
+      year: "numeric",
+      month: "2-digit",
+      day: "2-digit",
+      hour: "2-digit",
+      minute: "2-digit",
+      hourCycle: "h23",
+      timeZoneName: "short",
+    };
+    if (options?.displaySeconds) {
+      intlOptions.second = "2-digit";
+    }
+    const parts = new Intl.DateTimeFormat("en-US", intlOptions).formatToParts(date);
+    const pick = (type: string) => parts.find((part) => part.type === type)?.value;
+    const yyyy = pick("year");
+    const mm = pick("month");
+    const dd = pick("day");
+    const hh = pick("hour");
+    const min = pick("minute");
+    const sec = options?.displaySeconds ? pick("second") : undefined;
+    const tz = [...parts]
+      .toReversed()
+      .find((part) => part.type === "timeZoneName")
+      ?.value?.trim();
+    if (!yyyy || !mm || !dd || !hh || !min) {
+      return undefined;
+    }
+    if (options?.displaySeconds && sec) {
+      return `${yyyy}-${mm}-${dd} ${hh}:${min}:${sec}${tz ? ` ${tz}` : ""}`;
+    }
+    return `${yyyy}-${mm}-${dd} ${hh}:${min}${tz ? ` ${tz}` : ""}`;
+  } catch {
     return undefined;
   }
-  if (options?.displaySeconds && sec) {
-    return `${yyyy}-${mm}-${dd} ${hh}:${min}:${sec}${tz ? ` ${tz}` : ""}`;
-  }
-  return `${yyyy}-${mm}-${dd} ${hh}:${min}${tz ? ` ${tz}` : ""}`;
 }

src/infra/format-time/format-time.test.ts

@@ -8,6 +8,12 @@ import {
 } from "./format-duration.js";
 import { formatTimeAgo, formatRelativeTimestamp } from "./format-relative.js";
 
+const invalidDurationInputs = [null, undefined, -100] as const;
+
+afterEach(() => {
+  vi.restoreAllMocks();
+});
+
 describe("format-duration", () => {
   describe("formatDurationCompact", () => {
     it("returns undefined for null/undefined/non-positive", () => {
@@ -55,7 +61,7 @@ describe("format-duration", () => {
 
   describe("formatDurationHuman", () => {
     it("returns fallback for invalid duration input", () => {
-      for (const value of [null, undefined, -100]) {
+      for (const value of invalidDurationInputs) {
         expect(formatDurationHuman(value)).toBe("n/a");
       }
       expect(formatDurationHuman(null, "unknown")).toBe("unknown");
@@ -106,6 +112,12 @@ describe("format-duration", () => {
     it("supports seconds unit", () => {
       expect(formatDurationSeconds(2000, { unit: "seconds" })).toBe("2 seconds");
     });
+
+    it("clamps negative values and rejects non-finite input", () => {
+      expect(formatDurationSeconds(-1500, { decimals: 1 })).toBe("0s");
+      expect(formatDurationSeconds(NaN)).toBe("unknown");
+      expect(formatDurationSeconds(Infinity)).toBe("unknown");
+    });
   });
 });
 
@@ -152,13 +164,52 @@ describe("format-datetime", () => {
       const result = formatZonedTimestamp(date, options);
       expect(result).toMatch(expected);
     });
+
+    it("returns undefined when required Intl parts are missing", () => {
+      function MissingPartsDateTimeFormat() {
+        return {
+          formatToParts: () => [
+            { type: "month", value: "01" },
+            { type: "day", value: "15" },
+            { type: "hour", value: "14" },
+            { type: "minute", value: "30" },
+          ],
+        } as Intl.DateTimeFormat;
+      }
+
+      vi.spyOn(Intl, "DateTimeFormat").mockImplementation(
+        MissingPartsDateTimeFormat as unknown as typeof Intl.DateTimeFormat,
+      );
+
+      expect(formatZonedTimestamp(new Date("2024-01-15T14:30:00.000Z"), { timeZone: "UTC" })).toBe(
+        undefined,
+      );
+    });
+
+    it("returns undefined when Intl formatting throws", () => {
+      function ThrowingDateTimeFormat() {
+        return {
+          formatToParts: () => {
+            throw new Error("boom");
+          },
+        } as Intl.DateTimeFormat;
+      }
+
+      vi.spyOn(Intl, "DateTimeFormat").mockImplementation(
+        ThrowingDateTimeFormat as unknown as typeof Intl.DateTimeFormat,
+      );
+
+      expect(formatZonedTimestamp(new Date("2024-01-15T14:30:00.000Z"), { timeZone: "UTC" })).toBe(
+        undefined,
+      );
+    });
   });
 });
 
 describe("format-relative", () => {
   describe("formatTimeAgo", () => {
     it("returns fallback for invalid elapsed input", () => {
-      for (const value of [null, undefined, -100]) {
+      for (const value of invalidDurationInputs) {
         expect(formatTimeAgo(value)).toBe("unknown");
       }
       expect(formatTimeAgo(null, { fallback: "n/a" })).toBe("n/a");
@@ -240,5 +291,14 @@ describe("format-relative", () => {
     ])("$name", ({ offsetMs, options, expected }) => {
       expect(formatRelativeTimestamp(Date.now() + offsetMs, options)).toBe(expected);
     });
+
+    it("falls back to relative days when date formatting throws", () => {
+      expect(
+        formatRelativeTimestamp(Date.now() - 8 * 24 * 3600000, {
+          dateFallback: true,
+          timezone: "Invalid/Timezone",
+        }),
+      ).toBe("8d ago");
+    });
   });
 });