Initial commit

.circleci/config.yml

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+version: 2
+jobs:
+  build:
+    docker:
+      - image: node
+    steps:
+      - checkout
+      - run:
+          name: Install dependencies
+          command: |
+            yarn
+      - run:
+          name: Run Prettier
+          command: |
+            yarn prettier:check
+      - run:
+          name: Build
+          command: |
+            yarn tsc --noEmit
+      - run:
+          name: Run tests
+          command: |
+            yarn test
+
+workflows:
+  version: 2
+  build:
+    jobs:
+      - build

.gitignore

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+### https://raw.github.com/github/gitignore/72190ee30bd1e2ccc233222341435adacb7a6500/Node.gitignore
+
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# TypeScript v1 declaration files
+typings/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env
+
+# parcel-bundler cache (https://parceljs.org/)
+.cache
+
+# next.js build output
+.next
+
+# nuxt.js build output
+.nuxt
+
+# vuepress build output
+.vuepress/dist
+
+# Serverless directories
+.serverless
+
+/src/**/*.js
+
+lib/*
+!.keep

.npmignore

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+.keep

.prettierrc

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+parser: typescript
+printWidth: 120
+singleQuote: true
+tabWidth: 4
+trailingComma: all

README.md

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+# koa-path-canonicalizer
+
+[![npm version](https://img.shields.io/npm/v/koa-path-canonicalizer.svg?style=flat-square)](https://www.npmjs.com/package/koa-path-canonicalizer)
+[![CircleCI](https://circleci.com/gh/herp-inc/koa-path-canonicalizer.svg?style=shield)](https://circleci.com/gh/herp-inc/koa-path-canonicalizer)
+
+A Koa middleware to redirect to canonicalized path
+
+## Installation
+
+```console
+$ yarn add koa-path-canonicalizer
+```
+
+## Usage
+
+```javascript
+const Koa = require('koa');
+const { pathCanonicalizer } = require('koa-path-canonicalizer');
+
+const app = new Koa();
+
+app.use(pathCanonicalizer());
+```
+
+## License
+
+The MIT License (MIT)

bin/prerelease.sh

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+#!/bin/sh -eu
+
+yarn install
+rm -rf ./lib/*
+yarn tsc -d --outDir ./lib
+cp .npmignore package.json README.md ./lib

jest.config.js

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+module.exports = {
+    moduleFileExtensions: ['js', 'json', 'jsx', 'node', 'ts', 'tsx'],
+    testRegex: '(\\.|/)(test|spec)\\.tsx?$',
+    transform: {
+        '^.+\\.tsx?$': 'ts-jest',
+    },
+};

package.json

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+{
+  "name": "koa-path-canonicalizer",
+  "version": "0.1.0",
+  "description": "A Koa middleware to redirect to canonicalized path",
+  "main": "index.js",
+  "repository": "https://github.com/herp-inc/koa-path-canonicalizer.git",
+  "author": "Ryota Kameoka <ryota.kameoka@herp.co.jp>",
+  "license": "MIT",
+  "typings": "index.d.ts",
+  "devDependencies": {
+    "@types/jest": "^23.3.4",
+    "@types/koa": "^2.0.46",
+    "@types/node": "^10.11.5",
+    "@types/supertest": "^2.0.6",
+    "jest": "^23.6.0",
+    "koa": "^2.5.3",
+    "prettier": "^1.14.3",
+    "supertest": "^3.3.0",
+    "ts-jest": "^23.10.4",
+    "typescript": "^3.1.1"
+  },
+  "scripts": {
+    "prerelease": "./bin/prerelease.sh",
+    "prettier:check": "prettier --list-different src/**/*.ts",
+    "prettier:format": "prettier --write src/**/*.ts",
+    "test": "jest"
+  }
+}

src/canonicalize.test.ts

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+import { canonicalize } from './canonicalize';
+
+describe(canonicalize, () => {
+    it('returns null when the given path is /', () => {
+        expect(canonicalize('/')).toBeNull();
+    });
+
+    it('returns / when the given path is //', () => {
+        expect(canonicalize('//')).toBe('/');
+    });
+
+    it('returns null when the given path is already canonical', () => {
+        expect(canonicalize('/api/v1/users/42')).toBeNull();
+    });
+
+    it('eliminates trailing slashes', () => {
+        expect(canonicalize('/api/v1/users/42/')).toBe('/api/v1/users/42');
+        expect(canonicalize('/api/v1/users/42//')).toBe('/api/v1/users/42');
+        expect(canonicalize('/api/v1/users/42///')).toBe('/api/v1/users/42');
+    });
+
+    it('folds multiple slashes into one', () => {
+        expect(canonicalize('//api/v1/users/42')).toBe('/api/v1/users/42');
+        expect(canonicalize('/api/v1//users//42')).toBe('/api/v1/users/42');
+        expect(canonicalize('/api/v1///users///42')).toBe('/api/v1/users/42');
+    });
+});

src/canonicalize.ts

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+const SLASHES = new RegExp('//+', 'g');
+
+/**
+ * Canonicalize the given path. Returns null if the given path is already canonical.
+ * @param path
+ */
+export function canonicalize(path: string): string | null {
+    if (path === '/') {
+        return null;
+    }
+
+    let newPath = path;
+
+    if (newPath.includes('//')) {
+        newPath = newPath.replace(SLASHES, '/');
+    }
+
+    if (newPath !== '/' && newPath.endsWith('/')) {
+        newPath = newPath.slice(0, -1);
+    }
+
+    return newPath === path ? null : newPath;
+}

src/index.test.ts

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+import * as Koa from 'koa';
+import { Server } from 'http';
+import * as request from 'supertest';
+
+import { pathCanonicalizer } from './';
+
+describe(pathCanonicalizer, () => {
+    let app: Koa;
+    let server: Server;
+
+    beforeAll(() => {
+        app = new Koa();
+        app.use(pathCanonicalizer());
+        app.use(async (ctx, next) => {
+            if (ctx.path === '/' || ctx.path === '/api/v1/users/42') {
+                ctx.status = 200;
+                ctx.body = 'Hello, world!';
+                await next();
+            }
+        });
+
+        server = app.listen();
+    });
+
+    afterAll(() => server.close());
+
+    const get = (path: string) => request(server).get(path);
+
+    describe('when the path is canonical', () => {
+        describe('/', () => {
+            it('returns 200', async () => {
+                const res = await get('/');
+                expect(res.status).toBe(200);
+            });
+        });
+
+        describe('/api/v1/users/42', () => {
+            it('returns 200', async () => {
+                const res = await get('/api/v1/users/42');
+                expect(res.status).toBe(200);
+            });
+        });
+    });
+
+    describe('when the path is non-canonical', () => {
+        describe('//', () => {
+            it('redirects to /', async () => {
+                const res = await get('//');
+                expect(res.status).toBe(302);
+                expect(res.header['location']).toBe('/');
+            });
+        });
+
+        describe('//api////v1/users////42', () => {
+            it('redirects to /api/v1/users/42', async () => {
+                const res = await get('//api////v1/users////42');
+                expect(res.status).toBe(302);
+                expect(res.header['location']).toBe('/api/v1/users/42');
+            });
+        });
+    });
+});

src/index.ts

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+import { Middleware, Context } from 'koa';
+
+import { canonicalize } from './canonicalize';
+
+/**
+ * A Koa middleware to redirect to canonicalized path
+ */
+export function pathCanonicalizer(): Middleware {
+    return async function(ctx: Context, next: () => Promise<void>): Promise<void> {
+        const newPath = canonicalize(ctx.path);
+
+        if (newPath === null) {
+            await next();
+        } else {
+            ctx.redirect(newPath);
+        }
+    };
+}

tsconfig.json

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+{
+  "compilerOptions": {
+    "module": "commonjs",
+    "noFallthroughCasesInSwitch": true,
+    "noImplicitReturns": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "strict": true,
+    "target": "esnext"
+  },
+  "exclude": [
+    "./src/**/*.test.ts"
+  ]
+}