Zenn
Open19

Hono, Elysiaとかのモダンフレームワークでエラーを正しくRPCに乗せたい

Hono
ElysiaJS
巳波みなと巳波みなと

ゴール

HonoやElysiaが提供するRPC（End to End Typesafe）にミドルウェアやサービスが返すエラーを正しく乗せてあげたい

巳波みなと巳波みなと

次に、ミドルウェアやサービスで返したエラーを、OpenAPIの定義にレスポンスとして追加してみた。

結果、SwaggerUI（うちはScaler使ってるけど）には表示されたが、RPCには乗らなかった

巳波みなと巳波みなと

HonoでRPCに乗っけるにはこうするしかなさそう？

server.ts
import { Hono } from "hono";
import { serve } from "@hono/node-server";

// Server
const app = new Hono().get("/:id", (c) => {
    if (c.req.param("id") === "1") {
        return c.json({ message: "Hello World", errCode: 'NOT_FOUND' }, 404);
    }

    return c.json({ message: "Hello World" }, 200);

});

serve(app);
export type AppType = typeof app;
client.ts
import { hc } from "hono/client";
import { AppType } from "./index";

// Client
const client = hc<AppType>("http://localhost:3000");

const callClient = async () => {
  const res = await client[":id"].$get({ param: { id: "1" } });

  if (!res.ok) {
    if (res.status === 404) {
      const err = await res.json();
      console.log(err);
      return;
    }
  }

  console.log(await res.json());
};

callClient();

巳波みなと巳波みなと

このようにmiddlewareを追加するともちろん反映されない

server.ts
import { Hono } from "hono";
import { serve } from "@hono/node-server";

// Server
const app = new Hono()
    .use(async (c, next) => {
        const token = c.req.header("Authorization");
        if (token !== "1234567890") {
            return c.json({ message: "Unauthorized" }, 401);
        }
        await next();
    })
    .get("/:id", (c) => {
        if (c.req.param("id") === "1") {
            return c.json({ message: "Hello World", errCode: "NOT_FOUND" }, 404);
        }

        return c.json({ message: "Hello World" }, 200);
    });

serve(app);
export type AppType = typeof app;
client.ts
import { hc } from "hono/client";
import { AppType } from "./index";

// Client
const client = hc<AppType>("http://localhost:3000");

const callClient = async () => {
    const res = await client[":id"].$get({ param: { id: "1" } }, {
        headers: {
            Authorization: "1234567890",
        }
    });

    if (!res.ok) {
        if (res.status === 404) {
            const err = await res.json();
            console.log(err);
            return;
        }
    }

    console.log(await res.json());
};

callClient();

巳波みなと巳波みなと

throw new HTTPException もRPCには反映されない

server.ts
import { Hono } from "hono";
import { serve } from "@hono/node-server";
import { doSomething } from "./service";

// Server
const app = new Hono()
    .use(async (c, next) => {
        const token = c.req.header("Authorization");
        if (token !== "1234567890") {
            return c.json({ message: "Unauthorized" }, 401);
        }
        await next();
    })
    .get("/:id", async (c) => {
        const res = await doSomething(c.req.param("id"));

        if (c.req.param("id") === "2") {
            return c.json({ message: "Hello World", errCode: "NOT_FOUND" }, 404);
        }

        return c.json(res, 200);
    });

serve(app);
export type AppType = typeof app;
client.ts
import { hc } from "hono/client";
import { AppType } from "./index";

// Client
const client = hc<AppType>("http://localhost:3000");

const callClient = async () => {
    const res = await client[":id"].$get({ param: { id: "1" } }, {
        headers: {
            Authorization: "1234567890",
        }
    });

    if (!res.ok) {
        if (res.status === 404) {
            const err = await res.json();
            console.log(err);
            return;
        }
    }

    console.log(await res.json());
};

callClient();
service.ts
import { HTTPException } from "hono/http-exception";

export const doSomething = async (id: string) => {
    if (id === "1") {
        throw new HTTPException(400, {
            message: "Bad Request",
        });
    }

    return {
        message: "Hello World",
    };
};

巳波みなと巳波みなと

ちなみにtsconfig.jsonは初期状態

tsconfig.json
{
  "compilerOptions": {
    /* Visit https://aka.ms/tsconfig to read more about this file */

    /* Projects */
    // "incremental": true,                              /* Save .tsbuildinfo files to allow for incremental compilation of projects. */
    // "composite": true,                                /* Enable constraints that allow a TypeScript project to be used with project references. */
    // "tsBuildInfoFile": "./.tsbuildinfo",              /* Specify the path to .tsbuildinfo incremental compilation file. */
    // "disableSourceOfProjectReferenceRedirect": true,  /* Disable preferring source files instead of declaration files when referencing composite projects. */
    // "disableSolutionSearching": true,                 /* Opt a project out of multi-project reference checking when editing. */
    // "disableReferencedProjectLoad": true,             /* Reduce the number of projects loaded automatically by TypeScript. */

    /* Language and Environment */
    "target": "es2016",                                  /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
    // "lib": [],                                        /* Specify a set of bundled library declaration files that describe the target runtime environment. */
    // "jsx": "preserve",                                /* Specify what JSX code is generated. */
    // "libReplacement": true,                           /* Enable lib replacement. */
    // "experimentalDecorators": true,                   /* Enable experimental support for legacy experimental decorators. */
    // "emitDecoratorMetadata": true,                    /* Emit design-type metadata for decorated declarations in source files. */
    // "jsxFactory": "",                                 /* Specify the JSX factory function used when targeting React JSX emit, e.g. 'React.createElement' or 'h'. */
    // "jsxFragmentFactory": "",                         /* Specify the JSX Fragment reference used for fragments when targeting React JSX emit e.g. 'React.Fragment' or 'Fragment'. */
    // "jsxImportSource": "",                            /* Specify module specifier used to import the JSX factory functions when using 'jsx: react-jsx*'. */
    // "reactNamespace": "",                             /* Specify the object invoked for 'createElement'. This only applies when targeting 'react' JSX emit. */
    // "noLib": true,                                    /* Disable including any library files, including the default lib.d.ts. */
    // "useDefineForClassFields": true,                  /* Emit ECMAScript-standard-compliant class fields. */
    // "moduleDetection": "auto",                        /* Control what method is used to detect module-format JS files. */

    /* Modules */
    "module": "commonjs",                                /* Specify what module code is generated. */
    // "rootDir": "./",                                  /* Specify the root folder within your source files. */
    // "moduleResolution": "node10",                     /* Specify how TypeScript looks up a file from a given module specifier. */
    // "baseUrl": "./",                                  /* Specify the base directory to resolve non-relative module names. */
    // "paths": {},                                      /* Specify a set of entries that re-map imports to additional lookup locations. */
    // "rootDirs": [],                                   /* Allow multiple folders to be treated as one when resolving modules. */
    // "typeRoots": [],                                  /* Specify multiple folders that act like './node_modules/@types'. */
    // "types": [],                                      /* Specify type package names to be included without being referenced in a source file. */
    // "allowUmdGlobalAccess": true,                     /* Allow accessing UMD globals from modules. */
    // "moduleSuffixes": [],                             /* List of file name suffixes to search when resolving a module. */
    // "allowImportingTsExtensions": true,               /* Allow imports to include TypeScript file extensions. Requires '--moduleResolution bundler' and either '--noEmit' or '--emitDeclarationOnly' to be set. */
    // "rewriteRelativeImportExtensions": true,          /* Rewrite '.ts', '.tsx', '.mts', and '.cts' file extensions in relative import paths to their JavaScript equivalent in output files. */
    // "resolvePackageJsonExports": true,                /* Use the package.json 'exports' field when resolving package imports. */
    // "resolvePackageJsonImports": true,                /* Use the package.json 'imports' field when resolving imports. */
    // "customConditions": [],                           /* Conditions to set in addition to the resolver-specific defaults when resolving imports. */
    // "noUncheckedSideEffectImports": true,             /* Check side effect imports. */
    // "resolveJsonModule": true,                        /* Enable importing .json files. */
    // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
    // "noResolve": true,                                /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

    /* JavaScript Support */
    // "allowJs": true,                                  /* Allow JavaScript files to be a part of your program. Use the 'checkJS' option to get errors from these files. */
    // "checkJs": true,                                  /* Enable error reporting in type-checked JavaScript files. */
    // "maxNodeModuleJsDepth": 1,                        /* Specify the maximum folder depth used for checking JavaScript files from 'node_modules'. Only applicable with 'allowJs'. */

    /* Emit */
    // "declaration": true,                              /* Generate .d.ts files from TypeScript and JavaScript files in your project. */
    // "declarationMap": true,                           /* Create sourcemaps for d.ts files. */
    // "emitDeclarationOnly": true,                      /* Only output d.ts files and not JavaScript files. */
    // "sourceMap": true,                                /* Create source map files for emitted JavaScript files. */
    // "inlineSourceMap": true,                          /* Include sourcemap files inside the emitted JavaScript. */
    // "noEmit": true,                                   /* Disable emitting files from a compilation. */
    // "outFile": "./",                                  /* Specify a file that bundles all outputs into one JavaScript file. If 'declaration' is true, also designates a file that bundles all .d.ts output. */
    // "outDir": "./",                                   /* Specify an output folder for all emitted files. */
    // "removeComments": true,                           /* Disable emitting comments. */
    // "importHelpers": true,                            /* Allow importing helper functions from tslib once per project, instead of including them per-file. */
    // "downlevelIteration": true,                       /* Emit more compliant, but verbose and less performant JavaScript for iteration. */
    // "sourceRoot": "",                                 /* Specify the root path for debuggers to find the reference source code. */
    // "mapRoot": "",                                    /* Specify the location where debugger should locate map files instead of generated locations. */
    // "inlineSources": true,                            /* Include source code in the sourcemaps inside the emitted JavaScript. */
    // "emitBOM": true,                                  /* Emit a UTF-8 Byte Order Mark (BOM) in the beginning of output files. */
    // "newLine": "crlf",                                /* Set the newline character for emitting files. */
    // "stripInternal": true,                            /* Disable emitting declarations that have '@internal' in their JSDoc comments. */
    // "noEmitHelpers": true,                            /* Disable generating custom helper functions like '__extends' in compiled output. */
    // "noEmitOnError": true,                            /* Disable emitting files if any type checking errors are reported. */
    // "preserveConstEnums": true,                       /* Disable erasing 'const enum' declarations in generated code. */
    // "declarationDir": "./",                           /* Specify the output directory for generated declaration files. */

    /* Interop Constraints */
    // "isolatedModules": true,                          /* Ensure that each file can be safely transpiled without relying on other imports. */
    // "verbatimModuleSyntax": true,                     /* Do not transform or elide any imports or exports not marked as type-only, ensuring they are written in the output file's format based on the 'module' setting. */
    // "isolatedDeclarations": true,                     /* Require sufficient annotation on exports so other tools can trivially generate declaration files. */
    // "erasableSyntaxOnly": true,                       /* Do not allow runtime constructs that are not part of ECMAScript. */
    // "allowSyntheticDefaultImports": true,             /* Allow 'import x from y' when a module doesn't have a default export. */
    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
    // "preserveSymlinks": true,                         /* Disable resolving symlinks to their realpath. This correlates to the same flag in node. */
    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */

    /* Type Checking */
    "strict": true,                                      /* Enable all strict type-checking options. */
    // "noImplicitAny": true,                            /* Enable error reporting for expressions and declarations with an implied 'any' type. */
    // "strictNullChecks": true,                         /* When type checking, take into account 'null' and 'undefined'. */
    // "strictFunctionTypes": true,                      /* When assigning functions, check to ensure parameters and the return values are subtype-compatible. */
    // "strictBindCallApply": true,                      /* Check that the arguments for 'bind', 'call', and 'apply' methods match the original function. */
    // "strictPropertyInitialization": true,             /* Check for class properties that are declared but not set in the constructor. */
    // "strictBuiltinIteratorReturn": true,              /* Built-in iterators are instantiated with a 'TReturn' type of 'undefined' instead of 'any'. */
    // "noImplicitThis": true,                           /* Enable error reporting when 'this' is given the type 'any'. */
    // "useUnknownInCatchVariables": true,               /* Default catch clause variables as 'unknown' instead of 'any'. */
    // "alwaysStrict": true,                             /* Ensure 'use strict' is always emitted. */
    // "noUnusedLocals": true,                           /* Enable error reporting when local variables aren't read. */
    // "noUnusedParameters": true,                       /* Raise an error when a function parameter isn't read. */
    // "exactOptionalPropertyTypes": true,               /* Interpret optional property types as written, rather than adding 'undefined'. */
    // "noImplicitReturns": true,                        /* Enable error reporting for codepaths that do not explicitly return in a function. */
    // "noFallthroughCasesInSwitch": true,               /* Enable error reporting for fallthrough cases in switch statements. */
    // "noUncheckedIndexedAccess": true,                 /* Add 'undefined' to a type when accessed using an index. */
    // "noImplicitOverride": true,                       /* Ensure overriding members in derived classes are marked with an override modifier. */
    // "noPropertyAccessFromIndexSignature": true,       /* Enforces using indexed accessors for keys declared using an indexed type. */
    // "allowUnusedLabels": true,                        /* Disable error reporting for unused labels. */
    // "allowUnreachableCode": true,                     /* Disable error reporting for unreachable code. */

    /* Completeness */
    // "skipDefaultLibCheck": true,                      /* Skip type checking .d.ts files that are included with TypeScript. */
    "skipLibCheck": true                                 /* Skip type checking all .d.ts files. */
  }
}

RPCを効かせるためには、 "strict": true, である必要がある

巳波みなと巳波みなと

あとRPCを効かせるためには、サーバーはすべてメソッドチェーンで記述する必要がある

✅OK

server.ts
import { Hono } from "hono";
import { serve } from "@hono/node-server";
import { doSomething } from "./service";

// Server
const app = new Hono()
    .use(async (c, next) => {
        const token = c.req.header("Authorization");
        if (token !== "1234567890") {
            return c.json({ message: "Unauthorized" }, 401);
        }
        await next();
    })
    .get("/:id", async (c) => {
        const res = await doSomething(c.req.param("id"));

        if (c.req.param("id") === "2") {
            return c.json({ message: "Hello World", errCode: "NOT_FOUND" }, 404);
        }

        return c.json(res, 200);
    });

serve(app);
export type AppType = typeof app;

❌ NG

server.ts
import { Hono } from "hono";
import { serve } from "@hono/node-server";
import { doSomething } from "./service";

// Server
const app = new Hono()

app.use(async (c, next) => {
    const token = c.req.header("Authorization");
    if (token !== "1234567890") {
        return c.json({ message: "Unauthorized" }, 401);
    }
    await next();
})

app.get("/:id", async (c) => {
    const res = await doSomething(c.req.param("id"));

    if (c.req.param("id") === "2") {
        return c.json({ message: "Hello World", errCode: "NOT_FOUND" }, 404);
    }

    return c.json(res, 200);
});

serve(app);
export type AppType = typeof app;

巳波みなと巳波みなと

もちろん親で HTTPException をthrowしてもRPCには含まれない

server.ts
import { Hono } from "hono";
import { serve } from "@hono/node-server";
import { doSomething } from "./service";
import { HTTPException } from "hono/http-exception";

// Server
const app = new Hono()
    .use(async (c, next) => {
        const token = c.req.header("Authorization");
        if (token !== "1234567890") {
            return c.json({ message: "Unauthorized" }, 401);
        }
        await next();
    })
    .get("/:id", async (c) => {
        const res = await doSomething(c.req.param("id"));

        if (c.req.param("id") === "2") {
            throw new HTTPException(404, {
                message: "Not Found",
            });
        }

        return c.json(res, 200);
    });

serve(app);
export type AppType = typeof app;

巳波みなと巳波みなと

onError でエラーレスポンスを返しても、RPCには含まれない

server.ts
import { Hono } from "hono";
import { serve } from "@hono/node-server";
import { doSomething } from "./service";
import { HTTPException } from "hono/http-exception";

// Server
const app = new Hono()
    .use(async (c, next) => {
        const token = c.req.header("Authorization");
        if (token !== "1234567890") {
            return c.json({ message: "Unauthorized" }, 401);
        }
        await next();
    })
    .onError((err, c) => {
        if (err instanceof HTTPException) {
            return err.getResponse();
        }

        return c.json({ message: "Internal Server Error" }, 500);
    })
    .get("/:id", async (c) => {
        const res = await doSomething(c.req.param("id"));

        if (c.req.param("id") === "2") {
            return c.json({ message: "Hello World", errCode: "NOT_FOUND" }, 404);
        }

        return c.json(res, 200);
    });

serve(app);
export type AppType = typeof app;

(clientとserviceは以前のものと同一だが、serviceで返している400も、onErrorで返している500も、いずれもRPCには含まれていない)

巳波みなと巳波みなと

ドキュメント上でも、親から返すことを想定されているように見える

https://hono.dev/docs/guides/rpc#not-found

notfound.ts
export const routes = new Hono().get(
  '/posts',
  zValidator(
    'query',
    z.object({
      id: z.string(),
    })
  ),
  async (c) => {
    const { id } = c.req.valid('query')
    const post: Post | undefined = await getPost(id)

    if (post === undefined) {
      return c.json({ error: 'not found' }, 404) // Specify 404
    }

    return c.json({ post }, 200) // Specify 200
  }
)
巳波みなと巳波みなと

つまり、なんらかの形で子から親にエラーを伝えて（try catchや、データがなかったらエラーと見做す、など）、そのエラーをレスポンスとして返してあげる必要がある。

そうすると、エラーの分岐が多いサービスや、必須の認証などは、いちいち書いてあげる必要があるのでかなり面倒。

しかもRPCに乗ってないと、エラーハンドリングができない。

server.ts
import { Hono } from "hono";
import { serve } from "@hono/node-server";
import { doSomething } from "./service";
import { HTTPException } from "hono/http-exception";

// Server
const app = new Hono()
    .use(async (c, next) => {
        const token = c.req.header("Authorization");
        if (token !== "1234567890") {
            return c.json({ message: "Unauthorized" }, 401);
        }
        await next();
    })
    .onError((err, c) => {
        if (err instanceof HTTPException) {
            return err.getResponse();
        }

        return c.json({ message: "Internal Server Error" }, 500);
    })
    .get("/:id", async (c) => {
        const res = await doSomething(c.req.param("id"));

        if (c.req.param("id") === "2") {
            return c.json({ message: "Hello World", errCode: "NOT_FOUND" }, 404);
        }

        return c.json(res, 200);
    });

serve(app);
export type AppType = typeof app;
client.ts
import { hc } from "hono/client";
import { AppType } from "./index";

// Client
const client = hc<AppType>("http://localhost:3000");

const callClient = async () => {
    const res = await client[":id"].$get({ param: { id: "1" } }, {
        headers: {
            Authorization: "1234567890",
        }
    });

    if (!res.ok) {
        if (res.status === 400) {
            const err = await res.json();
            console.log(err);
            return;
        }
    }

    console.log(await res.json());
};

callClient();
service.ts
import { HTTPException } from "hono/http-exception";

export const doSomething = async (id: string) => {
    if (id === "1") {
        throw new HTTPException(400, {
            message: "Bad Request",
        });
    }

    return {
        message: "Hello World",
    };
};

Serviceから返している400がRPCに乗っていないので、型エラーでフロントエンドで処理できない

巳波みなと巳波みなと

一応、@hono/zod-openapi を使用すれば、事前にエラーを定義しておくことができます。

https://zenn.dev/link/comments/721354af028526

これに関しては、これで解決できます。

server.ts
import { OpenAPIHono } from "@hono/zod-openapi";
import { createRoute } from "@hono/zod-openapi";
import { z } from "zod";
import { serve } from "@hono/node-server";

const route = createRoute({
    method: "get",
    path: "/",
    responses: {
        200: {
            description: "Success",
            content: {
                "application/json": {
                    schema: z.object({
                        message: z.string(),
                    }),
                },
            },
        },
        404: {
            description: "Not Found",
            content: {
                "application/json": {
                    schema: z.object({
                        message: z.string(),
                    }),
                },
            },
        },
        500: {
            description: "Internal Server Error",
            content: {
                "application/json": {
                    schema: z.object({
                        message: z.string(),
                    }),
                },
            },
        },
    },
});

const app = new OpenAPIHono().openapi(route, (c) => {
    return c.json({ message: "Hello World" }, 200);
});

serve(app);
export type AppType = typeof app;
client.ts
import { hc } from "hono/client";
import { AppType } from "./index";

// Client
const client = hc<AppType>("http://localhost:3000");

const callClient = async () => {
    const res = await client.index.$get();

    if (!res.ok) {
        if (res.status === 404) {
            const err = await res.json();
            console.log(err);
            return;
        }
    }

    console.log(await res.json());
};

callClient();

createRouteで定義したものが正しく反映されてますね。
ただ、定義と実態が乖離していても、エラーにはならない点は微妙だなとは思いますが。

こんな感じで、無視してフィールドを書いても型エラーにはなりません。

巳波みなと巳波みなと

tRPCも使ってみたいけど、RESTっぽくなさすぎてさすがにちょっと学習コストが高そうだ

巳波みなと巳波みなと

Hono OpenAPIだとそもそも型情報にOpenAPIの定義が乗ってきません（冒頭のあれの再確認）

巳波みなと巳波みなと

ちなみに、成功レスポンスに対してStatusCodeを定義しなければ、クライアント側では、どのStatusCodeが来るかわからない（≒StatusCodeだけ実質any状態）にできるので、エラーハンドリング自体は型エラーなしにできます。

巳波みなと巳波みなと

じゃあこれでいいのかと言われたら、型安全ってなに？ということになると個人的には思いますけどね

巳波みなと巳波みなと

めっちゃゆるくやるなら

・エラーレスポンスはOpenAPIで定義しておいて、SwaggerUIとかで見てフロントエンドはハンドリングする
・成功レスポンスだけRPCに乗せて、成功レスポンスは型安全にする
・エラーハンドリングは型安全ではないけど、すべてHTTPExceptionとかでthrowしてあげて、RPCには載せず、SwaggerUI上で判断する

とかになるのかな。