From f4262e2cc659409b938e6fcd933f8f213d5375a8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc-Andr=C3=A9=20Bombeck?= <mbombeck@gmail.com>
Date: Tue, 20 Oct 2026 09:51:13 +0200
Subject: [PATCH] test(guards): see a squared two-argument distance as a
 hand-rolled spread

---
 ...spread-single-implementation-guard.test.ts | 20 +++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/__tests__/spread-single-implementation-guard.test.ts b/src/__tests__/spread-single-implementation-guard.test.ts
index 46b5dfa5a..cf7191b6e 100644
--- a/src/__tests__/spread-single-implementation-guard.test.ts
+++ b/src/__tests__/spread-single-implementation-guard.test.ts
@@ -20,7 +20,7 @@ import { readFileSync } from "node:fs";
 import { join } from "node:path";
 import { describe, expect, it } from "vitest";
 
-import { walkSourceFiles } from "./helpers/source-files";
+import { stripComments, walkSourceFiles } from "./helpers/source-files";
 
 const SRC = join(process.cwd(), "src");
 
@@ -32,14 +32,17 @@ const ALLOWED: Record<string, string> = {
   "lib/insights/mood-pattern-cards.ts": "A pooled variance for a t statistic.",
   "lib/insights/derived/trajectory.ts":
     "The residual standard error of a regression fit (÷ n − 2).",
+  "lib/insights/derived/sleep-score.ts":
+    "A circular SD of the sleep midpoint around its circular mean, the input of the consistency score; `spread` has no circular distance, and the score is never shown as a spread.",
 };
 
+/**
+ * A squared deviation: `(x - m) ** 2`, `(x - m) * (x - m)`, or a two-argument
+ * distance squared, `dist(x, m) ** 2` (a circular or otherwise custom
+ * deviation is still a hand-rolled spread).
+ */
 const SQUARED_DEVIATION =
-  /\(\s*[\w.[\]]+\s*-\s*[\w.[\]]+\s*\)\s*\*\*\s*2|\(\s*([\w.[\]]+)\s*-\s*([\w.[\]]+)\s*\)\s*\*\s*\(\s*\1\s*-\s*\2\s*\)/;
-
-function stripComments(text: string): string {
-  return text.replace(/\/\*[\s\S]*?\*\//g, "").replace(/^\s*\/\/.*$/gm, "");
-}
+  /\(\s*[\w.[\]]+\s*-\s*[\w.[\]]+\s*\)\s*\*\*\s*2|\(\s*([\w.[\]]+)\s*-\s*([\w.[\]]+)\s*\)\s*\*\s*\(\s*\1\s*-\s*\2\s*\)|\b[A-Za-z_]\w*\s*\(\s*[\w.[\]]+\s*,\s*[\w.[\]]+\s*\)\s*\*\*\s*2/;
 
 function computesSpread(code: string): boolean {
   return SQUARED_DEVIATION.test(code) && code.includes("Math.sqrt(");
@@ -59,6 +62,11 @@ describe("one standard deviation", () => {
     expect(
       computesSpread("acc += (v - mean) * (v - mean); Math.sqrt(acc / n);"),
     ).toBe(true);
+    expect(
+      computesSpread(
+        "xs.reduce((s, v) => s + circularMinuteDistance(v, mean) ** 2, 0); Math.sqrt(x);",
+      ),
+    ).toBe(true);
   });
 
   it("no file outside the list computes its own", () => {