fix: better error handling

Author: MathurAditya724

package.json

@@ -123,4 +123,4 @@
     "vitest": "^3.2.4"
   },
   "packageManager": "pnpm@10.0.0"
-}
+}

src/handlers.ts

@@ -2,8 +2,8 @@ import type { StandardSchemaV1 } from "@standard-schema/spec";
 import { quansync } from "quansync";
 import { getToJsonSchemaFn } from "./vendors/index.js";
 import {
-  errorMessageWrapper,
   type ToJsonSchemaFn,
+  UnsupportedVendorError,
   validationMapper,
 } from "./vendors/utils.js";
 
@@ -12,14 +12,11 @@ import {
  */
 export const toJsonSchema = quansync({
   sync: (schema: StandardSchemaV1, options?: Record<string, unknown>) => {
-    const fn = validationMapper.get(schema["~standard"].vendor);
+    const vendor = schema["~standard"].vendor;
+    const fn = validationMapper.get(vendor);
 
     if (!fn) {
-      throw new Error(
-        errorMessageWrapper(
-          `Unsupported schema vendor "${schema["~standard"].vendor}".`,
-        ),
-      );
+      throw new UnsupportedVendorError(vendor);
     }
 
     return fn(schema, options);

src/index.ts

@@ -1,2 +1,2 @@
 export * from "./handlers.js";
-export type { ToJsonSchemaFn } from "./vendors/utils.js";
+export type { ToJsonSchemaFn } from "./vendors/utils.js";

src/vendors/effect.ts

@@ -1,13 +1,13 @@
 import type { Schema } from "effect";
 import type { JSONSchema7 } from "json-schema";
-import { errorMessageWrapper, type ToJsonSchemaFn } from "./utils.js";
+import { MissingDependencyError, type ToJsonSchemaFn } from "./utils.js";
 
 export default async function getToJsonSchemaFn(): Promise<ToJsonSchemaFn> {
   try {
     const { JSONSchema } = await import("effect");
     return (schema) =>
       JSONSchema.make(schema as Schema.Schema<unknown>) as JSONSchema7;
   } catch {
-    throw new Error(errorMessageWrapper('Missing dependencies "effect".'));
+    throw new MissingDependencyError("effect");
   }
 }

src/vendors/index.ts

@@ -1,6 +1,6 @@
 import {
-  errorMessageWrapper,
   type ToJsonSchemaFn,
+  UnsupportedVendorError,
   validationMapper,
 } from "./utils.js";
 
@@ -28,9 +28,7 @@ export const getToJsonSchemaFn = async (
       vendorFnPromise = (await import("./zod.js")).default();
       break;
     default:
-      throw new Error(
-        errorMessageWrapper(`Unsupported schema vendor "${vendor}".`),
-      );
+      throw new UnsupportedVendorError(vendor);
   }
 
   const vendorFn = await vendorFnPromise;

src/vendors/utils.ts

@@ -4,7 +4,16 @@ export type ToJsonSchemaFn = (
   options?: Record<string, unknown>,
 ) => JSONSchema7 | Promise<JSONSchema7>;
 
-export const errorMessageWrapper = (message: string) =>
-  `standard-json: ${message}`;
-
 export const validationMapper = new Map<string, ToJsonSchemaFn>();
+
+export class UnsupportedVendorError extends Error {
+  constructor(vendor: string) {
+    super(`standard-json: Unsupported schema vendor "${vendor}".`);
+  }
+}
+
+export class MissingDependencyError extends Error {
+  constructor(packageName: string) {
+    super(`standard-json: Missing dependencies "${packageName}".`);
+  }
+}

src/vendors/valibot.ts

@@ -1,12 +1,10 @@
-import { errorMessageWrapper, type ToJsonSchemaFn } from "./utils.js";
+import { MissingDependencyError, type ToJsonSchemaFn } from "./utils.js";
 
 export default async function getToJsonSchemaFn(): Promise<ToJsonSchemaFn> {
   try {
     const { toJsonSchema } = await import("@valibot/to-json-schema");
     return toJsonSchema as ToJsonSchemaFn;
   } catch {
-    throw new Error(
-      errorMessageWrapper('Missing dependencies "@valibot/to-json-schema".'),
-    );
+    throw new MissingDependencyError("@valibot/to-json-schema");
   }
 }

src/vendors/zod.ts

@@ -1,6 +1,8 @@
 import type { ZodTypeAny } from "zod/v3";
 import type { $ZodType } from "zod/v4/core";
-import { errorMessageWrapper, type ToJsonSchemaFn } from "./utils.js";
+import { MissingDependencyError, type ToJsonSchemaFn } from "./utils.js";
+
+const zodv4Error = new MissingDependencyError("zod v4");
 
 export default async function getToJsonSchemaFn(): Promise<ToJsonSchemaFn> {
   return async (schema, options) => {
@@ -9,21 +11,21 @@ export default async function getToJsonSchemaFn(): Promise<ToJsonSchemaFn> {
     // https://zod.dev/library-authors?id=how-to-support-zod-and-zod-mini-simultaneously#how-to-support-zod-3-and-zod-4-simultaneously
     if ("_zod" in (schema as $ZodType | ZodTypeAny)) {
       try {
-        handler = await import("zod/v4/core").then(
-          (mod) => mod.toJSONSchema as ToJsonSchemaFn,
-        );
+        handler = await import("zod/v4/core")
+          .catch(() => {
+            throw zodv4Error;
+          })
+          .then((mod) => mod.toJSONSchema as ToJsonSchemaFn);
       } catch {
-        throw new Error(errorMessageWrapper('Missing dependencies "zod v4".'));
+        throw zodv4Error;
       }
     } else {
       try {
         handler = await import("zod-to-json-schema").then(
           (mod) => mod.zodToJsonSchema as ToJsonSchemaFn,
         );
       } catch {
-        throw new Error(
-          errorMessageWrapper('Missing dependencies "zod-to-json-schema".'),
-        );
+        throw new MissingDependencyError("zod-to-json-schema");
       }
     }