Quick Start
Plugins
Quick Start
Plugins

Error Handling

Teasim catches all the errors thrown in the handler, classifies the error code, and pipes them to onError middleware.

new Teasim()
  .onError(({ code, error }) => {
    return new Response(error.toString());
  })
  .get("/", () => {
    throw new Error("Server is during maintainance");

    return "unreachable";
  });

With onError you can catch and transform the error into your custom error message.

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It's important that onError must be called before the handler you want to apply it to.

For example, returning custom 404 messages:

import { Teasim, NotFoundError } from "teasim";

new Teasim()
  .onError(({ code, error, set }) => {
    if (code === "NOT_FOUND") {
      set.status = 404;

      return "Not Found :(";
    }
  })
  .post("/", () => {
    throw new NotFoundError();
  })
  .listen(8080);

Local Error

You can assign an error handling method to a scope using hook or guard

app.get("/", () => "Hello", {
  beforeHandle({ set, request: { headers } }) {
    if (!isSignIn(headers)) {
      set.status = 401;

      throw new Error("Unauthorized");
    }
  },
  error({ error }) {
    return "Handled";
  },
});

Custom Error Message

You can provide a custom error message by providing error:

new Teasim().post("/", ({ body }) => body, {
  body: t.Object({
    name: t.String({
      error: "Name is required",
    }),
    age: t.Number(),
  }),
});

Error Code

Teasim error code consists of:

  • NOT_FOUND
  • INTERNAL_SERVER_ERROR
  • VALIDATION
  • PARSE
  • UNKNOWN

By default, user thrown error code is unknown.

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If no error response is returned, the error will be returned using error.name.

Custom Error

Teasim supports custom error both in the type-level and implementation level.

Helping you to easily classify and narrow down the error type for full type safety with auto-complete:

class CustomError extends Error {
  constructor(public message: string) {
    super(message);
  }
}

new Teasim()
  .addError({
    MyError: CustomError,
  })
  .onError(({ code, error }) => {
    switch (code) {
      // With auto-completion
      case "MyError":
        // With type narrowing
        // Error is typed as CustomError
        return error;
    }
  })
  .get("/", () => {
    throw new CustomError("Hello Error");
  });

Catching all error

To list all errors, you can list an error using error.all.

new Teasim().post("/", ({ body }) => body, {
  body: t.Object({
    name: t.String(),
    age: t.Number(),
  }),
  error({ code, error }) {
    switch (code) {
      case "VALIDATION":
        console.log(error.all);

        // Find a specific error name (path is OpenAPI Schema compliance)
        const name = error.all.find(x => x.path === "/name");

        // If has validation error, then log it
        if (name) console.log(name);
    }
  },
});

With this you can overwrite provide an advance custom error message or monitor an error based on your need.

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Make sure to narrow down Error code to "Validation" to narrow down error type before using error.all