From 1f87ce7682225afc821934a3d86139320e08100c Mon Sep 17 00:00:00 2001
From: Thomas Lamant <tom@tmlmt.com>
Date: Sun, 25 Oct 2026 20:53:07 +0100
Subject: [PATCH] fix(recipe): collect RatioNotComputableError(E9401 during
 final quantity aggregation

---
 docs/e/codes/COOKLANG_E9401.md |  4 +++-
 src/classes/recipe.ts          |  8 +++++++-
 test/diagnostics.test.ts       | 26 ++++++++++++++++++++++++++
 test/parser_helpers.test.ts    |  6 +++---
 test/recipe_parsing.test.ts    | 12 +++++++++++-
 5 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/docs/e/codes/COOKLANG_E9401.md b/docs/e/codes/COOKLANG_E9401.md
index dd608463..f2938a5b 100644
--- a/docs/e/codes/COOKLANG_E9401.md
+++ b/docs/e/codes/COOKLANG_E9401.md
@@ -6,12 +6,14 @@ title: Ratio cannot be computed
 
 ## What this error means
 
-The ratio between two quantities cannot be computed because one of them is not numeric. This aborts the whole `parse()`/`scaleBy()`/`convertTo()` call; it is not collected alongside other diagnostics.
+The ratio between two quantities cannot be computed because one of them is not numeric. 
 
 ## Common causes
 
 - Merging equivalents where one of the equivalent quantities is text-only, e.g. `@flour{1%cup|a bit}` then `@&flour{2%cup|a lot}`
 
+During `Recipe.parse()`, this is collected with the other diagnostics and thrown after the source has been processed. During `scaleBy()` or `convertTo()`, it is thrown directly by the operation that needs the ratio.
+
 ## How to fix it
 
 Use numeric quantities for every equivalent that needs to be merged with another occurrence of the same ingredient.
diff --git a/src/classes/recipe.ts b/src/classes/recipe.ts
index ec6e9be5..126eafa1 100644
--- a/src/classes/recipe.ts
+++ b/src/classes/recipe.ts
@@ -88,6 +88,7 @@ import {
   ReferencedItemCannotBeRedefinedError,
   NoTabAsIndentError,
   BadIndentationError,
+  RatioNotComputableError,
   DiagnosticError,
   ParseStoppedError,
 } from "../errors";
@@ -2095,7 +2096,12 @@ export class Recipe {
       this.choices.variants = [...allVariants];
     }
 
-    this._populateIngredientQuantities(true);
+    try {
+      this._populateIngredientQuantities(true);
+    } catch (error) {
+      if (!(error instanceof RatioNotComputableError)) throw error;
+      this.diagnostics.push(error.diagnostic);
+    }
 
     // Diagnostics are reported in source order (sort is stable)
     this.diagnostics.sort(
diff --git a/test/diagnostics.test.ts b/test/diagnostics.test.ts
index f5dc1618..ba24f2df 100644
--- a/test/diagnostics.test.ts
+++ b/test/diagnostics.test.ts
@@ -399,4 +399,30 @@ describe("Recipe.parse() throwing", () => {
       times: 1,
     });
   });
+
+  it("collects COOKLANG_E9401 with the source during final quantity aggregation", () => {
+    const source = "Add @flour{1%cup|a bit}\nAdd @&flour{2%cup|a lot}";
+    const recipe = new Recipe();
+    let thrown: unknown;
+
+    try {
+      recipe.parse(source);
+    } catch (error) {
+      thrown = error;
+    }
+
+    expect(thrown).toBeInstanceOf(DiagnosticError);
+    expect(thrown).toMatchObject({
+      source,
+      diagnostics: [
+        {
+          code: "COOKLANG_E9401",
+          severity: "error",
+        },
+      ],
+    });
+    expect(recipe.diagnostics).toEqual((thrown as DiagnosticError).diagnostics);
+    expect(recipe.ingredients).toHaveLength(1);
+    expect(recipe.sections).toHaveLength(1);
+  });
 });
diff --git a/test/parser_helpers.test.ts b/test/parser_helpers.test.ts
index 92a47fd1..a811cb9a 100644
--- a/test/parser_helpers.test.ts
+++ b/test/parser_helpers.test.ts
@@ -940,9 +940,9 @@ describe("findAndUpsertCookware", () => {
       },
     };
 
-    expect(() => findAndUpsertCookware(cookware, newCookware, true)).toThrow(
-      DivisionByZeroError,
-    );
+    expect(() =>
+      findAndUpsertCookware(cookware, newCookware, true, []),
+    ).toThrow(DivisionByZeroError);
   });
 
   it("should throw a ReferencedCookwareNotFoundError if a reference cookware does not exist", () => {
diff --git a/test/recipe_parsing.test.ts b/test/recipe_parsing.test.ts
index 8d8f285c..3eb4e29d 100644
--- a/test/recipe_parsing.test.ts
+++ b/test/recipe_parsing.test.ts
@@ -1,6 +1,6 @@
 import { describe, it, expect } from "vitest";
 import { Recipe } from "../src/classes/recipe";
-import { ParseStoppedError } from "../src/errors";
+import { DiagnosticError, ParseStoppedError } from "../src/errors";
 import { parseCollect } from "./mocks/parse_collect";
 import {
   simpleRecipe,
@@ -77,6 +77,16 @@ describe("parse function", () => {
       });
     });
 
+    it("rethrows unexpected errors during final quantity aggregation", () => {
+      const recipe = new Recipe();
+      const unexpected = new Error("Unexpected aggregation failure");
+      Reflect.set(recipe, "_populateIngredientQuantities", () => {
+        throw unexpected;
+      });
+
+      expect(() => recipe.parse("@flour")).toThrow(unexpected);
+    });
+
     it("stops immediately with COOKLANG_E1003 for a zero-denominator fraction", () => {
       const source = "Add @flour{1/0}\nAdd @sugar{2}";
       const recipe = new Recipe();