Expand assert to use message: string | () => string (#39)

* Expand assert to use message: string | () => string

* Update docs

package.json

@@ -29,7 +29,7 @@
     "test": "jest --coverage"
   },
   "devDependencies": {
-    "@polkadot/api-jsonrpc": "^0.5.9",
+    "@polkadot/api-jsonrpc": "^0.5.11",
     "@polkadot/dev": "^0.12.6"
   },
   "dependencies": {

src/assert.js

@@ -2,10 +2,11 @@
 // @flow
 
 const ExtError = require('./ext/error');
+const isFunction = require('./is/function');
 
 /**
   @name assert
-  @signature assert (test: boolean, message: string, code: number = ExtError.CODES.ASSERT, data: any): void
+  @signature assert (test: any, message: string | () => string, code: number = ExtError.CODES.ASSERT, data: any): void
   @summary Checks for a valid test, if not ExtError is thrown.
   @description
     Checks that `test` is a truthy value. If value is falsy (`null`, `undefined`, `false`, ...), it throws an ExtError with the supplied `message` and an optional `code` and `data`. When `test` passes, `true` is returned.
@@ -14,11 +15,16 @@ const ExtError = require('./ext/error');
 
     assert(true, 'True should be true'); // true returned
     assert(false, 'False should not be true'); // ExtError thrown
+    assert(false, () => 'message'); // ExtError with 'message'
 */
-module.exports = function assert (test: any, message: string, code: number = ExtError.CODES.ASSERT, data: any): boolean {
+module.exports = function assert (test: any, message: string | () => string, code: number = ExtError.CODES.ASSERT, data: any): boolean {
   if (test) {
     return true;
   }
 
-  throw new ExtError(message, code, data);
+  if (isFunction(message)) {
+    message = ((message: any): () => string)();
+  }
+
+  throw new ExtError(((message: any): string), code, data);
 };

src/assert.spec.js

@@ -15,6 +15,12 @@ describe('assert', () => {
     ).toThrow(/error thrown/);
   });
 
+  it('should throw an error when message: () => string', () => {
+    expect(
+      () => assert(false, () => 'message from function')
+    ).toThrow(/message from function/);
+  });
+
   it('throws a valid constructed ExtError', () => {
     try {
       assert(false, 'error', -666, { some: 'data' });

src/bn/toHex.js

@@ -3,6 +3,7 @@
 
 const BN = require('bn.js');
 
+const assert = require('../assert');
 const hexAddPrefix = require('../hex/addPrefix');
 const isBN = require('../is/bn');
 
@@ -25,9 +26,7 @@ module.exports = function bnToHex (value?: BN): string {
     return ZERO_STR;
   }
 
-  if (!isBN(value)) {
-    throw new Error(`Cannot convert from non-BN value '${(value: any)}' to hex`);
-  }
+  assert(isBN(value), `Cannot convert from non-BN value '${(value: any)}' to hex`);
 
   return hexAddPrefix(value.toString(16));
 };

src/buffer/toHex.js

@@ -1,6 +1,7 @@
 // ISC, Copyright 2017 Jaco Greeff
 // @flow
 
+const assert = require('../assert');
 const isBuffer = require('../is/buffer');
 const hexAddPrefix = require('../hex/addPrefix');
 
@@ -22,9 +23,7 @@ module.exports = function bufferToHex (value?: Buffer): string {
     return ZERO_HEX;
   }
 
-  if (!isBuffer(value)) {
-    throw new Error(`Cannot convert non-buffer to hex`);
-  }
+  assert(isBuffer(value), `Cannot convert non-buffer to hex`);
 
   return hexAddPrefix(
     value.toString('hex')

src/buffer/toU8a.js

@@ -1,6 +1,7 @@
 // ISC, Copyright 2017 Jaco Greeff
 // @flow
 
+const assert = require('../assert');
 const isBuffer = require('../is/buffer');
 
 /**
@@ -19,9 +20,7 @@ module.exports = function bufferToU8a (buffer?: Buffer): Uint8Array {
     return new Uint8Array([]);
   }
 
-  if (!isBuffer(buffer)) {
-    throw new Error('Cannot convert non-buffer to Uint8Array');
-  }
+  assert(isBuffer(buffer), 'Cannot convert non-buffer to Uint8Array');
 
   const array = new Uint8Array(buffer.length);
 

src/hex/toBn.js

@@ -3,6 +3,7 @@
 
 const BN = require('bn.js');
 
+const assert = require('../assert');
 const hexStripPrefix = require('./stripPrefix');
 const isHex = require('../is/hex');
 
@@ -24,9 +25,7 @@ module.exports = function hexToBn (value?: string): BN {
     return ZERO_BN;
   }
 
-  if (!isHex(value)) {
-    throw new Error(`Cannot convert from non-hex value '${value}' to BN`);
-  }
+  assert(isHex(value), `Cannot convert from non-hex value '${value}' to BN`);
 
   return new BN(hexStripPrefix(value), 16);
 };

src/hex/toBuffer.js

@@ -1,11 +1,10 @@
 // ISC, Copyright 2017 Jaco Greeff
 // @flow
 
+const assert = require('../assert');
 const isHex = require('../is/hex');
 const hexStripPrefix = require('./stripPrefix');
 
-const EMPTY_BUFFER = Buffer.from([]);
-
 /**
   @name hexToBuffer
   @signature hexToBuffer (value?: string): Buffer
@@ -19,12 +18,10 @@ const EMPTY_BUFFER = Buffer.from([]);
 */
 module.exports = function hexToBuffer (value?: string): Buffer {
   if (!value) {
-    return EMPTY_BUFFER;
+    return Buffer.from([]);
   }
 
-  if (!isHex(value)) {
-    throw new Error(`Cannot convert non-hex value '${value}' to Buffer`);
-  }
+  assert(isHex(value), `Cannot convert non-hex value '${value}' to Buffer`);
 
   return Buffer.from(hexStripPrefix(value), 'hex');
 };

src/number/toBuffer.js

@@ -15,7 +15,7 @@ const numberToHex = require('./toHex');
   @example
     import { numberToBuffer } from '@polkadot/util';
 
-    const buffer = numberToBuffer('0x1234'); // => Buffer.from([0x12, 0x34])
+    const buffer = numberToBuffer(0x1234); // => Buffer.from([0x12, 0x34])
 */
 module.exports = function numberToBuffer (value?: number): Buffer {
   if (isUndefined(value) || isNull(value) || isNaN(value)) {

src/u8a/toBuffer.js

@@ -1,10 +1,9 @@
 // ISC, Copyright 2017 Jaco Greeff
 // @flow
 
+const assert = require('../assert');
 const isUint8Array = require('../is/uint8Array');
 
-const EMPTY_BUFFER = Buffer.from([]);
-
 /**
   @name u8aToBuffer
   @signature u8aToBuffer (value?: UInt8Array): Buffer
@@ -18,12 +17,10 @@ const EMPTY_BUFFER = Buffer.from([]);
 */
 module.exports = function u8aToBuffer (value?: Uint8Array): Buffer {
   if (!value) {
-    return EMPTY_BUFFER;
+    return Buffer.from([]);
   }
 
-  if (!isUint8Array(value)) {
-    throw new Error('Cannot convert non-Uint8Array value to Buffer');
-  }
+  assert(isUint8Array(value), 'Cannot convert non-Uint8Array value to Buffer');
 
   return Buffer.from(value);
 };

yarn.lock

@@ -54,9 +54,9 @@
     lodash "^4.2.0"
     to-fast-properties "^2.0.0"
 
-"@polkadot/api-jsonrpc@^0.5.9":
-  version "0.5.9"
-  resolved "https://registry.yarnpkg.com/@polkadot/api-jsonrpc/-/api-jsonrpc-0.5.9.tgz#615311c4f7c73b95cb52e910250ecc712f695732"
+"@polkadot/api-jsonrpc@^0.5.11":
+  version "0.5.11"
+  resolved "https://registry.yarnpkg.com/@polkadot/api-jsonrpc/-/api-jsonrpc-0.5.11.tgz#a03190a8645c942a0893fa8ec1b4990432c62242"
   dependencies:
     babel-runtime "^6.26.0"