feat(codegen-ts): output-pattern expander for template codegen

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LuZWKnWzYGVnESijL7uuky

Author: dmealing

server/typescript/packages/codegen-ts/src/template-codegen/output-pattern.ts

@@ -0,0 +1,36 @@
+// Expands the tiny, fixed output-pattern grammar shared cross-port (SP-1 §3.3).
+// Placeholders: {name}, {Name} (PascalCase of name), {package} (:: → /).
+// An empty {package} collapses its trailing slash so `{package}/{name}` with no
+// package yields just `{name}`. Unknown placeholders are a hard error.
+
+const KNOWN = new Set(["name", "Name", "package"]);
+
+function pascalCase(s: string): string {
+  return s
+    .split(/[^A-Za-z0-9]+/)
+    .filter(Boolean)
+    .map((w) => w.charAt(0).toUpperCase() + w.slice(1))
+    .join("");
+}
+
+export function expandOutputPattern(
+  pattern: string,
+  vars: { name?: string; package?: string },
+): string {
+  let pkgWasEmpty = false;
+  const out = pattern.replace(/\{(\w+)\}/g, (_m, token: string) => {
+    if (!KNOWN.has(token)) {
+      throw new Error(`unknown placeholder {${token}} in output pattern '${pattern}'`);
+    }
+    if (token === "package") {
+      const p = (vars.package ?? "").replaceAll("::", "/");
+      if (p === "") pkgWasEmpty = true;
+      return p;
+    }
+    if (vars.name === undefined) {
+      throw new Error(`output pattern '${pattern}' uses {${token}} but no entity name is in scope`);
+    }
+    return token === "Name" ? pascalCase(vars.name) : vars.name;
+  });
+  return pkgWasEmpty ? out.replace(/^\/+/, "").replace(/\/{2,}/g, "/") : out;
+}

server/typescript/packages/codegen-ts/test/template-codegen/output-pattern.test.ts

@@ -0,0 +1,24 @@
+import { describe, test, expect } from "bun:test";
+import { expandOutputPattern } from "../../src/template-codegen/output-pattern.js";
+
+describe("expandOutputPattern", () => {
+  test("{name} and {package} (:: → /)", () => {
+    expect(expandOutputPattern("{package}/{name}Service.ts", { name: "order", package: "acme::sales" }))
+      .toBe("acme/sales/orderService.ts");
+  });
+  test("{Name} is PascalCase", () => {
+    expect(expandOutputPattern("{Name}.cs", { name: "order_line" })).toBe("OrderLine.cs");
+  });
+  test("literal pattern (perModel) passes through", () => {
+    expect(expandOutputPattern("registry.ts", {})).toBe("registry.ts");
+  });
+  test("empty package collapses to no leading slash", () => {
+    expect(expandOutputPattern("{package}/{name}.ts", { name: "x", package: "" })).toBe("x.ts");
+  });
+  test("unknown placeholder throws", () => {
+    expect(() => expandOutputPattern("{bogus}.ts", { name: "x" })).toThrow(/unknown placeholder/i);
+  });
+  test("{name} with no name var throws", () => {
+    expect(() => expandOutputPattern("{name}.ts", {})).toThrow(/name/i);
+  });
+});