feat(base-formula): add type checker

apps/server/src/core/base/formula/__tests__/typecheck.spec.ts

@@ -0,0 +1,33 @@
+// TODO: unskip after Task 15 lands date functions and populates the registry.
+import { parseRaw, resolve, typecheck, registry } from "@docmost/base-formula/server";
+import type { FormulaAST } from "@docmost/base-formula/server";
+
+const mk = (src: string, propTypes: Record<string, "number" | "string" | "boolean" | "date">) => {
+  const names = new Map(Object.keys(propTypes).map((n) => [n, `prop_${n.toLowerCase()}`]));
+  const resolved = resolve(parseRaw(src), names);
+  const typeMap = new Map(Object.entries(propTypes).map(([n, t]) => [`prop_${n.toLowerCase()}`, t]));
+  return { ast: resolved.ast, typeMap };
+};
+
+describe.skip("typecheck", () => {
+  it("infers number for arithmetic", () => {
+    const { ast, typeMap } = mk('prop("Price") * 2', { Price: "number" });
+    expect(typecheck(ast, typeMap, registry).resultType).toBe("number");
+  });
+  it("rejects string * number", () => {
+    const { ast, typeMap } = mk('prop("Name") * 2', { Name: "string" });
+    expect(() => typecheck(ast, typeMap, registry)).toThrow(/TYPE_MISMATCH/);
+  });
+  it("infers boolean for comparison", () => {
+    const { ast, typeMap } = mk('prop("Price") > 0', { Price: "number" });
+    expect(typecheck(ast, typeMap, registry).resultType).toBe("boolean");
+  });
+  it("infers string for concat()", () => {
+    const { ast, typeMap } = mk('concat(prop("Name"), "!")', { Name: "string" });
+    expect(typecheck(ast, typeMap, registry).resultType).toBe("string");
+  });
+  it("infers branch-join type for if()", () => {
+    const { ast, typeMap } = mk('if(true, prop("Price"), 0)', { Price: "number" });
+    expect(typecheck(ast, typeMap, registry).resultType).toBe("number");
+  });
+});