Fix #97 extending to async user configuration file (#99)

* extend loadConfig to accept promises

* add tests


* update README and docs

README.md

@@ -20,7 +20,10 @@ Sweeter, simpler and faster than Truffle.
   * `import "openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";`
 * Fixtures that help write fast and maintainable test suites, e.g.:
   * `const {token} = await loadFixture(standardTokenWithBalance);`
-* Sub-second compilation with native and dockerized solc
+* Customizable compilation options with native solc, dockerized solc and any version of solc-js loaded remotely at compiled time
+* Support for promise-based configuration, e.g.:
+  * use native solc binary for fast compilation in CI environment
+  * use solc-js based on contract versions detected (async)
 * Support for TypeScript
 * [Documentation](https://ethereum-waffle.readthedocs.io/en/latest/)
 

docs/source/configuration.rst

@@ -24,6 +24,18 @@ Configuration can also be of type js, e.g.:
 
 Native and dockerized solc compiler configuration is described in "Fast compilation" section.
 
+Configuration can even be a Promise in a js, e.g.:
+::
+
+  module.exports = new Promise((resolve, reject) => {
+    resolve({
+      "compiler": "native"
+    });
+  });
+
+.. hint::
+  This is a powerful feature if you want to asynchronously load different compliation configurations in different environments. 
+  For example, you can use native solc in CI for faster compilation, whereas deciding the exact solc-js version locally based on the contract versions being used, since many of those operations are asynchronous, you'll most likely be returning a Promise to waffle to handle. 
 
 Solcjs and version management
 -----------------------------

lib/compiler/compiler.ts

@@ -1,4 +1,4 @@
-import {Config} from '../config/config';
+import defaultConfig, {Config} from '../config/config';
 import {isWarningMessage} from '../utils';
 import {getCompileFunction} from './getCompileFunction';
 import {findInputs} from './findInputs';
@@ -9,7 +9,7 @@ import {ImportsFsEngine, resolvers} from '@resolver-engine/imports-fs';
 import {gatherSources} from '@resolver-engine/imports';
 
 export async function compileProject(configPath: string) {
-  await compileAndSave(loadConfig(configPath));
+  await compileAndSave(await loadConfig(configPath));
 }
 
 export async function compileAndSave(config: Config) {

lib/config/loadConfig.ts

@@ -8,9 +8,19 @@ function readConfigFile(configPath: string) {
   return {};
 }
 
-export function loadConfig(configPath: string): Config {
-  return {
-    ...defaultConfig,
-    ...readConfigFile(configPath)
-  };
+export async function loadConfig(configPath: string): Promise<Config> {
+  if (configPath) {
+    return new Promise(async (resolve, reject) => {
+      resolve({
+        ...defaultConfig,
+        ...await require(path.join(process.cwd(), configPath))
+      });
+    });
+  } else {
+    return new Promise((resolve, reject) => {
+      resolve({
+        ...defaultConfig
+      });
+    });
+  }
 }

test/compiler/e2e.ts

@@ -3,6 +3,7 @@ import fsx from 'fs-extra';
 import {join, resolve} from 'path';
 import {expect} from 'chai';
 import {compileProject} from '../../lib/compiler/compiler';
+import defaultConfig, {Config} from '../../lib/config/config';
 import {loadConfig} from '../../lib/config/loadConfig';
 import {readFileContent, isFile, deepCopy} from '../../lib/utils';
 import {deployContract, link, getWallets, createMockProvider} from '../../lib/waffle';
@@ -11,6 +12,7 @@ const configurations = [
   './test/projects/custom/config.js',
   './test/projects/custom/config_native.json',
   './test/projects/custom/config_docker.json',
+  './test/projects/custom/config_promise.js',
   './test/projects/custom_solidity_4/config_solcjs.json',
   './test/projects/custom_solidity_4/config_docker.json'
 ];
@@ -25,7 +27,7 @@ const artefacts = [
   'OneAndAHalf.json'
 ];
 
-describe('E2E: Compiler integration', () => {
+describe('E2E: Compiler integration', async () => {
   describe('docker: inside out directory structure', () => {
     before(async () => {
       fsx.removeSync('test/projects/insideOut/build');
@@ -46,7 +48,7 @@ describe('E2E: Compiler integration', () => {
   });
 
   for (const configurationPath of configurations)  {
-    const configuration = loadConfig(configurationPath) as any;
+    const configuration = await loadConfig(configurationPath) as any;
     const {name, targetPath, legacyOutput} = configuration;
 
     /* eslint-disable no-loop-func */

test/projects/custom/config_promise.js

@@ -0,0 +1,8 @@
+module.exports = new Promise((resolve, reject) => {
+  resolve({
+    name: "solidity 5, promise returned solcjs config",
+    sourcesPath: "./test/projects/custom/custom_contracts",
+    targetPath: "./test/projects/custom/custom_build",
+    npmPath: "./test/projects/custom/custom_node_modules"
+  });
+});