Add a watch option

Similar to the way psc-ide support works, the purs-loader now tolerates
compiler errors when the `watch` option is true. When webpack is being
run in watch mode the user can set `watch` to true in order to avoid
failing the webpack bundle creation when the PureScript compiler fails.

Resolves issue #66

Resolves issue #73

Resolves issue #74

Author: ethul

README.md

@@ -61,6 +61,7 @@ const loaderConfig = {
   bundleNamespace: 'PS',
   bundle: false,
   warnings: true,
+  watch: false, // indicates if webapck is in watch mode
   output: 'output',
   src: [
     path.join('src', '**', '*.purs'),

src/Psc.js

@@ -45,7 +45,12 @@ function compile(psModule) {
         if (errorMessage.length) {
           psModule.emitError(errorMessage);
         }
-        reject(new Error('compilation failed'))
+        if (options.watch) {
+          resolve(psModule);
+        }
+        else {
+          reject(new Error('compilation failed'))
+        }
       } else {
         const warningMessage = stderr.join('');
         if (options.warnings && warningMessage.length) {

src/index.js

@@ -46,6 +46,7 @@ module.exports = function purescriptLoader(source, map) {
     bundleNamespace: 'PS',
     bundle: false,
     warnings: true,
+    watch: false,
     output: 'output',
     src: [
       path.join('src', '**', '*.purs'),