fix(native): narrow a var()-valued font-family to its first family

src/__tests__/compiler/font-family.test.ts

@@ -0,0 +1,186 @@
+import { compile } from "react-native-css/compiler";
+
+const declarationsFor = (css: string, className: string) => {
+  const rules = new Map(compile(css).stylesheet().s ?? []).get(className);
+
+  return (rules ?? []).flatMap((rule) => rule.d ?? []);
+};
+
+const variablesFor = (css: string, className: string) => {
+  const rules = new Map(compile(css).stylesheet().s ?? []).get(className);
+
+  return (rules ?? []).flatMap((rule) => rule.v ?? []);
+};
+
+describe("the typed path", () => {
+  test("a literal stack narrows to its first family", () => {
+    expect(
+      declarationsFor(`.a { font-family: Inter, Helvetica, sans-serif; }`, "a"),
+    ).toStrictEqual([{ fontFamily: "Inter" }]);
+  });
+
+  test("the `font` shorthand narrows to its first family", () => {
+    expect(
+      declarationsFor(`.a { font: italic 12px Inter, Helvetica; }`, "a"),
+    ).toStrictEqual([
+      {
+        fontFamily: "Inter",
+        fontSize: 12,
+        fontStyle: "italic",
+        fontWeight: "normal",
+      },
+    ]);
+  });
+
+  test("a name that is not a bare ident survives whole", () => {
+    // LightningCSS unquotes a quoted family, and a multi-ident name is one family
+    expect(
+      declarationsFor(`.a { font-family: "Helvetica Neue", Arial; }`, "a"),
+    ).toStrictEqual([{ fontFamily: "Helvetica Neue" }]);
+    expect(
+      declarationsFor(`.a { font-family: "Foo, Bar", Arial; }`, "a"),
+    ).toStrictEqual([{ fontFamily: "Foo, Bar" }]);
+    expect(
+      declarationsFor(`.a { font-family: Helvetica Neue, Arial; }`, "a"),
+    ).toStrictEqual([{ fontFamily: "Helvetica Neue" }]);
+  });
+
+  test("no warning is emitted for the families that are dropped", () => {
+    expect(
+      compile(`.a { font-family: Inter, Helvetica, sans-serif; }`).warnings(),
+    ).toStrictEqual({});
+    expect(
+      compile(`.a { font-family: Inter, Helvetica,; }`).warnings(),
+    ).toStrictEqual({});
+  });
+});
+
+describe("the unparsed path", () => {
+  test.each([
+    ["a trailing comma", `.a { font-family: Inter, Helvetica,; }`],
+    ["a leading comma", `.a { font-family: ,Inter, Helvetica; }`],
+    ["a doubled comma", `.a { font-family: Inter,,Helvetica; }`],
+    ["quoted families", `.a { font-family: "Inter", "Helvetica",; }`],
+  ])("%s still narrows to the first family", (_name, css) => {
+    expect(declarationsFor(css, "a")).toStrictEqual([{ fontFamily: "Inter" }]);
+  });
+
+  test("a quoted name keeps its spaces and its commas", () => {
+    expect(
+      declarationsFor(`.a { font-family: "Helvetica Neue", Arial,; }`, "a"),
+    ).toStrictEqual([{ fontFamily: "Helvetica Neue" }]);
+    expect(
+      declarationsFor(`.a { font-family: "Foo, Bar", Arial,; }`, "a"),
+    ).toStrictEqual([{ fontFamily: "Foo, Bar" }]);
+  });
+
+  test("an entry that cannot name a family is skipped", () => {
+    expect(
+      declarationsFor(`.a { font-family: 12, Inter; }`, "a"),
+    ).toStrictEqual([{ fontFamily: "Inter" }]);
+  });
+
+  test("a stack with nothing usable emits no declaration at all", () => {
+    expect(declarationsFor(`.a { font-family: ,; }`, "a")).toStrictEqual([]);
+  });
+
+  test("a keyframe narrows too", () => {
+    expect(
+      compile(
+        `@keyframes k { from { font-family: Inter, Helvetica,; } to { font-family: Georgia; } }`,
+      ).stylesheet().k,
+    ).toStrictEqual([
+      [
+        "k",
+        [
+          ["from", [{ fontFamily: "Inter" }]],
+          ["to", [{ fontFamily: "Georgia" }]],
+        ],
+      ],
+    ]);
+  });
+});
+
+describe("the var() path", () => {
+  // A variable declared once is inlined by the compiler, so these declare --stack twice
+
+  test("a stack the compiler cannot see is left for the runtime", () => {
+    expect(
+      declarationsFor(
+        `:root { --stack: Inter, Helvetica; } .other { --stack: Georgia, serif; } .a { font-family: var(--stack); }`,
+        "a",
+      ),
+    ).toStrictEqual([[[{}, "var", "stack", 1], "fontFamily", 1]]);
+  });
+
+  test("a var() behind a literal is narrowed away", () => {
+    expect(
+      declarationsFor(
+        `:root { --x: Georgia; } .other { --x: Verdana; } .a { font-family: Inter, var(--x); }`,
+        "a",
+      ),
+    ).toStrictEqual([{ fontFamily: "Inter" }]);
+  });
+
+  test("a var() in front of a literal is left whole", () => {
+    expect(
+      declarationsFor(
+        `:root { --x: Georgia; } .other { --x: Verdana; } .a { font-family: var(--x), Helvetica; }`,
+        "a",
+      ),
+    ).toStrictEqual([[[[{}, "var", "x", 1], "Helvetica"], "fontFamily"]]);
+  });
+
+  test("a fallback is emitted whole, whatever shape it has", () => {
+    expect(
+      declarationsFor(`.a { font-family: var(--missing, Helvetica); }`, "a"),
+    ).toStrictEqual([
+      [[{}, "var", ["missing", "Helvetica"], 1], "fontFamily", 1],
+    ]);
+
+    expect(
+      declarationsFor(
+        `.a { font-family: var(--missing, Inter, Helvetica); }`,
+        "a",
+      ),
+    ).toStrictEqual([
+      [[{}, "var", ["missing", ["Inter", "Helvetica"]], 1], "fontFamily", 1],
+    ]);
+
+    expect(
+      declarationsFor(
+        `.a { font-family: var(--missing-a, var(--missing-b, serif)); }`,
+        "a",
+      ),
+    ).toStrictEqual([
+      [
+        [{}, "var", ["missing-a", [{}, "var", ["missing-b", "serif"], 1]], 1],
+        "fontFamily",
+        1,
+      ],
+    ]);
+  });
+});
+
+describe("what a var() cannot carry", () => {
+  test("KNOWN LIMIT: a space group and a comma group compile to the same value", () => {
+    const spaceGroup = variablesFor(
+      `.b { --f: Helvetica Neue; } .c { --f: x; }`,
+      "b",
+    );
+    const commaGroup = variablesFor(
+      `.b { --f: Inter, Helvetica; } .c { --f: x; }`,
+      "b",
+    );
+
+    expect(spaceGroup).toStrictEqual([["f", ["Helvetica", "Neue"]]]);
+    expect(commaGroup).toStrictEqual([["f", ["Inter", "Helvetica"]]]);
+    expect(spaceGroup.map(([, value]) => typeof value)).toStrictEqual(
+      commaGroup.map(([, value]) => typeof value),
+    );
+
+    expect(
+      variablesFor(`.b { --f: "Helvetica Neue"; } .c { --f: x; }`, "b"),
+    ).toStrictEqual([["f", "Helvetica Neue"]]);
+  });
+});

src/__tests__/native/font-family-stack.test.ts

@@ -0,0 +1,83 @@
+import { applyValue } from "../../native/objects";
+
+/** A real Tailwind `--font-sans`, which is why the stack is the common case. */
+const FONT_SANS_STACK = [
+  "Inter",
+  "Inter Fallback",
+  "ui-sans-serif",
+  "system-ui",
+  "sans-serif",
+] as const;
+
+const applyFontFamily = (value: unknown): Record<string, unknown> => {
+  const target: Record<string, unknown> = {};
+  applyValue(target, "fontFamily", value);
+  return target;
+};
+
+describe("the reduction", () => {
+  test("a resolved stack reduces to its first family, as a string", () => {
+    const target = applyFontFamily([...FONT_SANS_STACK]);
+
+    expect(target.fontFamily).toBe("Inter");
+    expect(typeof target.fontFamily).toBe("string");
+  });
+
+  test("a nested stack is flattened, not descended into", () => {
+    expect(applyFontFamily([[...FONT_SANS_STACK]]).fontFamily).toBe("Inter");
+    expect(applyFontFamily([[], "Arial"]).fontFamily).toBe("Arial");
+    expect(applyFontFamily([[[]], "Arial"]).fontFamily).toBe("Arial");
+    expect(applyFontFamily([["Inter"], "Arial"]).fontFamily).toBe("Inter");
+  });
+
+  test("an entry that cannot name a family is skipped", () => {
+    expect(applyFontFamily([12, "Inter"]).fontFamily).toBe("Inter");
+    expect(applyFontFamily([null, "Arial"]).fontFamily).toBe("Arial");
+    expect(applyFontFamily([undefined, "Arial"]).fontFamily).toBe("Arial");
+    expect(applyFontFamily([true, "Arial"]).fontFamily).toBe("Arial");
+  });
+
+  test("a single family passes through untouched", () => {
+    expect(applyFontFamily("brand-icons").fontFamily).toBe("brand-icons");
+  });
+
+  test("a stack with nothing usable sets nothing", () => {
+    expect("fontFamily" in applyFontFamily([])).toBe(false);
+    expect("fontFamily" in applyFontFamily([12])).toBe(false);
+    expect("fontFamily" in applyFontFamily([[], [null]])).toBe(false);
+
+    const inherited: Record<string, unknown> = { fontFamily: "Inter" };
+    applyValue(inherited, "fontFamily", []);
+    expect(inherited.fontFamily).toBe("Inter");
+  });
+});
+
+describe("what the reduction must not disturb", () => {
+  test("the reduction is scoped to fontFamily", () => {
+    // fontVariant is a list on React Native, so only fontFamily is reduced
+    const target: Record<string, unknown> = {};
+    applyValue(target, "fontVariant", ["small-caps"]);
+
+    expect(target.fontVariant).toStrictEqual(["small-caps"]);
+  });
+
+  test("both sentinel meanings survive the reduction", () => {
+    const untouched: Record<string, unknown> = {};
+    applyValue(untouched, "fontFamily", undefined);
+    expect("fontFamily" in untouched).toBe(false);
+
+    const cleared: Record<string, unknown> = { fontFamily: "Inter" };
+    applyValue(cleared, "fontFamily", null);
+    expect("fontFamily" in cleared).toBe(true);
+    expect(cleared.fontFamily).toBeUndefined();
+  });
+
+  test("the delayed-style marker passes through by identity", () => {
+    // applyDeclarations parks { fontFamily: true } on the target while a delayed value resolves
+    const marker = { fontFamily: true };
+    const target: Record<string, unknown> = {};
+    applyValue(target, "fontFamily", marker);
+
+    expect(target.fontFamily).toBe(marker);
+  });
+});