Allow plugins to modify the config

__tests__/modifyConfig.test.js

@@ -0,0 +1,58 @@
+import postcss from 'postcss'
+import tailwind from '../src/index'
+
+test('plugins can add new theme values', () => {
+  return postcss([
+    tailwind({
+      corePlugins: [],
+      plugins: [
+        {
+          modifyConfig: function(config) {
+            return {
+              ...config,
+              theme: {
+                ...config.theme,
+                rotate: {
+                  '0': '0deg',
+                  '90': '90deg',
+                  '180': '180deg',
+                  '270': '270deg',
+                }
+              }
+            }
+          },
+          handler: function({ addUtilities, theme }) {
+            addUtilities(Object.entries(theme('rotate')).map(([key, value]) => {
+              return {
+                [`.rotate-${key}`]: {
+                  transform: `rotate(${value})`,
+                },
+              }
+            }))
+          },
+        }
+      ]
+    }),
+  ])
+    .process('@tailwind utilities;',
+      { from: undefined }
+    )
+    .then(result => {
+      const expected = `
+        .rotate-0 {
+          transform: rotate(0deg)
+        }
+        .rotate-90 {
+          transform: rotate(90deg)
+        }
+        .rotate-180 {
+          transform: rotate(180deg)
+        }
+        .rotate-270 {
+          transform: rotate(270deg)
+        }
+      `
+
+      expect(result.css).toMatchCss(expected)
+    })
+})

__tests__/processPlugins.test.js

@@ -47,7 +47,7 @@ test('plugins can create utilities with object syntax', () => {
         object-fit: cover
       }
     }
-    `)
+  `)
 })
 
 test('plugins can create utilities with arrays of objects', () => {
@@ -1206,3 +1206,41 @@ test('prefix will prefix all classes in a selector', () => {
     }
     `)
 })
+
+test('plugins can be provided as an object with a handler function', () => {
+  const { components, utilities } = processPlugins(
+    [
+      {
+        handler: function({ addUtilities }) {
+          addUtilities({
+            '.object-fill': {
+              'object-fit': 'fill',
+            },
+            '.object-contain': {
+              'object-fit': 'contain',
+            },
+            '.object-cover': {
+              'object-fit': 'cover',
+            },
+          })
+        },
+      }
+    ],
+    makeConfig()
+  )
+
+  expect(components.length).toBe(0)
+  expect(css(utilities)).toMatchCss(`
+    @variants {
+      .object-fill {
+        object-fit: fill
+      }
+      .object-contain {
+        object-fit: contain
+      }
+      .object-cover {
+        object-fit: cover
+      }
+    }
+  `)
+})

src/index.js

@@ -44,6 +44,12 @@ function resolveConfigPath(filePath) {
   }
 }
 
+function applyPluginConfigModifications(config) {
+  return [...config.plugins].reduce((modified, plugin) => {
+    return _.get(plugin, 'modifyConfig', _.identity)(modified)
+  }, config)
+}
+
 const getConfigFunction = config => () => {
   if (_.isUndefined(config) && !_.isObject(config)) {
     return resolveConfig([defaultConfig])
@@ -55,10 +61,9 @@ const getConfigFunction = config => () => {
     })
   }
 
-  return resolveConfig([
-    _.isObject(config) ? _.get(config, 'config', config) : require(config),
-    defaultConfig,
-  ])
+  const configObject = _.isObject(config) ? _.get(config, 'config', config) : require(config)
+
+  return resolveConfig([applyPluginConfigModifications(configObject), defaultConfig])
 }
 
 const plugin = postcss.plugin('tailwind', config => {

src/util/processPlugins.js

@@ -1,6 +1,7 @@
 import _ from 'lodash'
 import postcss from 'postcss'
 import Node from 'postcss/lib/node'
+import isFunction from 'lodash/isFunction'
 import escapeClassName from '../util/escapeClassName'
 import generateVariantFunction from '../util/generateVariantFunction'
 import parseObjectStyles from '../util/parseObjectStyles'
@@ -28,7 +29,9 @@ export default function(plugins, config) {
   const getConfigValue = (path, defaultValue) => _.get(config, path, defaultValue)
 
   plugins.forEach(plugin => {
-    plugin({
+    const handler = isFunction(plugin) ? plugin : plugin.handler
+
+    handler({
       postcss,
       config: getConfigValue,
       theme: (path, defaultValue) => getConfigValue(`theme.${path}`, defaultValue),