Initial commit.

.gitignore

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+# Logs
+log
+logs
+*.log
+npm-debug.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directory
+# https://docs.npmjs.com/misc/faq#should-i-check-my-node-modules-folder-into-git
+node_modules
+
+# OSX
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db
+.AppleDouble
+.LSOverride
+Icon
+
+# Pavlov
+dist

LICENSE

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+Copyright (c) 2015, Distributed Systems, Inc.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Makefile

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+# ==============================================================================
+# config
+
+.PHONY: default build clean format install lint publish test
+
+default: test
+
+WATCH ?= false
+
+# ==============================================================================
+# phony targets
+
+build:
+	./node_modules/.bin/babel src --ignore __tests__,__mocks__ --out-dir dist
+
+clean:
+	@- rm -rf node_modules
+
+format: | node_modules
+	./node_modules/.bin/standard --format src/**/*.js
+
+install:
+	npm install
+
+lint: | node_modules
+	./node_modules/.bin/standard src/**/*.js
+
+publish: build
+	npm publish
+
+test: | node_modules
+	@ if [ "$(WATCH)" = false ]; then \
+		./node_modules/.bin/jest; \
+	else \
+		./node_modules/.bin/jest --watch; \
+	fi
+
+# ==============================================================================
+# file targets
+
+node_modules:
+	npm install

package.json

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+{
+  "name": "invar",
+  "version": "1.0.0",
+  "description": "Runtime invariant checks for better errors.",
+  "license": "BSD-3-Clause",
+  "main": "src/index.js",
+  "scripts": {
+    "test": "make test"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/pavlovml/invar.git"
+  },
+  "bugs": {
+    "url": "https://github.com/pavlovml/invar/issues"
+  },
+  "engines": {
+    "node": ">= 5.0.0",
+    "npm": ">= 3.3.0"
+  },
+  "dependencies": {
+    "lodash": "^3.10.1"
+  },
+  "devDependencies": {
+    "babel-cli": "^6.2.0",
+    "babel-jest": "^6.0.1",
+    "babel-preset-es2015": "^6.1.18",
+    "babel-preset-stage-0": "^6.3.13",
+    "babel-eslint": "^4.1.5",
+    "eslint-plugin-babel": "^2.1.1",
+    "jest-cli": "^0.8.0",
+    "standard": "^5.4.1"
+  },
+  "babel": {
+    "presets": [
+      "es2015",
+      "stage-0"
+    ]
+  },
+  "jest": {
+    "scriptPreprocessor": "<rootDir>/node_modules/babel-jest",
+    "testPathDirs": [
+      "src"
+    ]
+  },
+  "standard": {
+    "parser": "babel-eslint",
+    "ignore": [
+      "dist"
+    ],
+    "global": [
+      "jest",
+      "describe",
+      "it",
+      "pit",
+      "expect",
+      "afterEach",
+      "beforeEach"
+    ]
+  }
+}

src/InvarError.js

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+export default class InvarError extends Error {
+  constructor (message, opts = {}) {
+    super(message)
+    this.name = 'Invariant Violation'
+    Object.assign(this, opts)
+  }
+}

src/__tests__/index.js

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+jest.dontMock('../InvarError')
+jest.dontMock('../index')
+jest.dontMock('json-stable-stringify')
+const invariant = require('../index').default
+
+describe('invariant', () => {
+  it('does nothing when the condition is truthy', () => {
+    expect(() => invariant(true, 'test')).not.toThrow()
+  })
+
+  it('throws an error when the condition is falsy', () => {
+    try {
+      invariant(false, 'test')
+      expect(false).toBeTruthy()
+    } catch (ex) {
+      expect(ex.name).toBe('Invariant Violation')
+      expect(ex.message).toBe('test')
+    }
+  })
+})
+
+describe('invariant.fail', () => {
+  it('always throws an error', () => {
+    try {
+      invariant(false, 'test')
+      expect(false).toBeTruthy()
+    } catch (ex) {
+      expect(ex.name).toBe('Invariant Violation')
+      expect(ex.message).toBe('test')
+    }
+  })
+})
+
+describe('invariant.equal', () => {
+  it('does nothing when the two values are equal', () => {
+    expect(() => invariant.equal('foo', 'foo', 'test')).not.toThrow()
+  })
+
+  it('throws an error when the two values are different', () => {
+    try {
+      invariant.equal('foo', 'bar', 'Lorem ipsum.')
+      expect(false).toBeTruthy()
+    } catch (ex) {
+      expect(ex.name).toBe('Invariant Violation')
+      expect(ex.message).toBe('Lorem ipsum.\n  Expected: "foo"\n  Actual:   "bar"')
+      expect(ex.expected).toBe('foo')
+      expect(ex.actual).toBe('bar')
+    }
+  })
+})

src/index.js

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+import InvarError from './InvarError'
+import _ from 'lodash'
+import stringify from 'json-stable-stringify'
+
+function makeInvarFnObj (obj) {
+  const fn = obj.invar
+
+  for (let k in obj) {
+    if (k !== 'invar') {
+      fn[k] = obj[k]
+    }
+  }
+
+  return fn
+}
+
+function throwError (message, opts) {
+  const stack =
+    `Invariant Violation: ${message}\n` +
+      (new Error()).stack
+      .split('\n')
+      .splice(3)
+      .join('\n')
+
+  throw new InvarError(
+    message,
+    _.defaults({ stack }, opts))
+}
+
+export default makeInvarFnObj({
+  invar (cond, message, opts = {}) {
+    if (!cond) {
+      throwError(message, opts)
+    }
+  },
+
+  fail (message, opts = {}) {
+    throwError(message, opts)
+  },
+
+  equal (expected, actual, message, opts = {}) {
+    if (!_.isEqual(expected, actual)) {
+      throwError(
+        `${message}\n  Expected: ${stringify(expected)}\n  Actual:   ${stringify(actual)}`,
+        _.defaults({ expected, actual }, opts))
+    }
+  }
+})