fix: enforce plugin config schemas (#1272) (thanks @thewilloftheshadow)

Co-authored-by: thewilloftheshadow <thewilloftheshadow@users.noreply.github.com>

src/plugins/schema-validator.ts

@@ -0,0 +1,40 @@
+import AjvPkg, { type ErrorObject, type ValidateFunction } from "ajv";
+
+const ajv = new (AjvPkg as unknown as new (opts?: object) => import("ajv").default)({
+  allErrors: true,
+  strict: false,
+  removeAdditional: false,
+});
+
+type CachedValidator = {
+  validate: ValidateFunction;
+  schema: Record<string, unknown>;
+};
+
+const schemaCache = new Map<string, CachedValidator>();
+
+function formatAjvErrors(errors: ErrorObject[] | null | undefined): string[] {
+  if (!errors || errors.length === 0) return ["invalid config"];
+  return errors.map((error) => {
+    const path = error.instancePath?.replace(/^\//, "").replace(/\//g, ".") || "<root>";
+    const message = error.message ?? "invalid";
+    return `${path}: ${message}`;
+  });
+}
+
+export function validateJsonSchemaValue(params: {
+  schema: Record<string, unknown>;
+  cacheKey: string;
+  value: unknown;
+}): { ok: true } | { ok: false; errors: string[] } {
+  let cached = schemaCache.get(params.cacheKey);
+  if (!cached || cached.schema !== params.schema) {
+    const validate = ajv.compile(params.schema) as ValidateFunction;
+    cached = { validate, schema: params.schema };
+    schemaCache.set(params.cacheKey, cached);
+  }
+
+  const ok = cached.validate(params.value);
+  if (ok) return { ok: true };
+  return { ok: false, errors: formatAjvErrors(cached.validate.errors) };
+}