Allow using a custom config with option to replace instead of default merging

src/index.js

@@ -1,6 +1,7 @@
 #!/usr/bin/env node
 
 import fs from 'fs'
+import _ from 'lodash'
 import path from 'path'
 import postcss from 'postcss'
 import defaultConfig from './defaultConfig'
@@ -11,38 +12,11 @@ let splitFileName = filename => {
   return filename.split('.')
 }
 
-program
-  .version('0.1.0')
-  .usage('[options] <file ...>')
-  .option('-c, --config [value]', 'Pass custom configuration')
-  .parse(process.argv)
-
-let inputFile = program.args[0]
-let outputFile =
-  program.args[1] || `${splitFileName(program.args[0])[0]}-output.css`
-
-if (!inputFile) {
-  console.error('No input file given!')
-  process.exit(1)
-}
-
-fs.readFile(path.join(program.config), (err, config) => {
-  if (err) {
-    console.error(`config file ${program.config} does not exist`)
-    process.exit(1)
-  }
-
-  const customConfig = JSON.parse(config.toString())
-
-  let finalConfig = {
-    ...defaultConfig,
-    ...customConfig,
-  }
-
+let buildTailwind = config => {
   console.log('Building Tailwind!')
 
   fs.readFile(inputFile, (err, css) => {
-    postcss([tailwind(finalConfig)])
+    postcss([tailwind(config)])
       .process(css)
       .then(result => {
         fs.writeFileSync(outputFile, result.css)
@@ -51,4 +25,58 @@ fs.readFile(path.join(program.config), (err, config) => {
   })
 
   console.log('Finished building Tailwind!')
-})
+}
+
+let getConfig = (customConfig, merge) => {
+  if (merge) {
+    return customConfig
+  } else {
+    return _.merge(defaultConfig, customConfig)
+  }
+}
+
+program
+  .version('0.1.0')
+  .usage('[options] <file ...>')
+  .option('-c, --config [path]', 'set config path')
+  .option(
+    '-r, --replace',
+    'replace the built-in configuration with the provided config file'
+  )
+  .parse(process.argv)
+
+let inputFile = program.args[0]
+
+if (!inputFile) {
+  console.error('No input file given!')
+  process.exit(1)
+}
+
+let outputFile =
+  program.args[1] || `${splitFileName(program.args[0])[0]}-output.css`
+
+if (program.config !== undefined) {
+  fs.exists(program.config, exists => {
+    if (!exists) {
+      console.error(`Config file [${program.config}] does not exist.`)
+      process.exit(1)
+    }
+
+    fs.readFile(program.config, (err, config) => {
+      if (err) {
+        console.error(
+          `There was a problem reading config file [${program.config}].`
+        )
+        process.exit(1)
+      }
+
+      const customConfig = JSON.parse(config.toString())
+
+      let finalConfig = getConfig(customConfig, program.replace)
+
+      buildTailwind(finalConfig)
+    })
+  })
+} else {
+  buildTailwind(defaultConfig)
+}