From d18fd513a4a09880e878252d76db59b5055c4a9c Mon Sep 17 00:00:00 2001
From: Jordan Pittman <jordan@cryptica.me>
Date: Thu, 15 Sep 2022 13:55:15 -0400
Subject: [PATCH] Add option to load config file relative to the input file

---
 src/featureFlags.js             |  1 +
 src/lib/setupTrackingContext.js |  6 ++---
 src/util/resolveConfigPath.js   | 44 ++++++++++++++++++++++++++++++---
 3 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/src/featureFlags.js b/src/featureFlags.js
index bd75108ea..fef84b149 100644
--- a/src/featureFlags.js
+++ b/src/featureFlags.js
@@ -15,6 +15,7 @@ let featureFlags = {
     'optimizeUniversalDefaults',
     'matchVariant',
     // 'variantGrouping',
+    'resolveConfigRelativeToInput',
   ],
 }
 
diff --git a/src/lib/setupTrackingContext.js b/src/lib/setupTrackingContext.js
index 37b42cdba..14cd92984 100644
--- a/src/lib/setupTrackingContext.js
+++ b/src/lib/setupTrackingContext.js
@@ -35,8 +35,8 @@ function getCandidateFiles(context, tailwindConfig) {
 }
 
 // Get the config object based on a path
-function getTailwindConfig(configOrPath) {
-  let userConfigPath = resolveConfigPath(configOrPath)
+function getTailwindConfig(configOrPath, inputPath) {
+  let userConfigPath = resolveConfigPath(configOrPath, inputPath)
 
   if (userConfigPath !== null) {
     let [prevConfig, prevConfigHash, prevDeps, prevModified] =
@@ -119,7 +119,7 @@ export default function setupTrackingContext(configOrPath) {
   return ({ tailwindDirectives, registerDependency }) => {
     return (root, result) => {
       let [tailwindConfig, userConfigPath, tailwindConfigHash, configDependencies] =
-        getTailwindConfig(configOrPath)
+        getTailwindConfig(configOrPath, result.opts.from)
 
       let contextDependencies = new Set(configDependencies)
 
diff --git a/src/util/resolveConfigPath.js b/src/util/resolveConfigPath.js
index 646a46fd4..f622f75f0 100644
--- a/src/util/resolveConfigPath.js
+++ b/src/util/resolveConfigPath.js
@@ -1,5 +1,6 @@
 import fs from 'fs'
 import path from 'path'
+import { flagEnabled } from '../featureFlags.js'
 
 function isObject(value) {
   return typeof value === 'object' && value !== null
@@ -13,7 +14,42 @@ function isString(value) {
   return typeof value === 'string' || value instanceof String
 }
 
-export default function resolveConfigPath(pathOrConfig) {
+/**
+ * This will take a possibly-relative path to a config and resolve
+ * it relative to the input path IF that config file exists and
+ * has the `resolveConfigRelativeToInput` flag enabled.
+ *
+ * If that file does not exist, or the flag is disabled, it will
+ * resolve the path relative to the current working directory.
+ *
+ * @param {string|undefined} inputPath
+ * @param {string} configPath
+ * @returns {string}
+ */
+function pickResolvedPath(configPath, inputPath) {
+  if (path.isAbsolute(configPath)) {
+    return configPath
+  }
+
+  if (inputPath) {
+    try {
+      // Use require.resolve so we can find config file in parent directories
+      let resolvedPath = require.resolve(configPath, {
+        paths: [inputPath],
+      })
+
+      let maybeConfig = require(resolvedPath)
+
+      if (typeof maybeConfig === 'object' && flagEnabled(maybeConfig, 'resolveConfigRelativeToInput')) {
+        return resolvedPath
+      }
+    } catch (e) {}
+  }
+
+  return path.resolve(configPath)
+}
+
+export default function resolveConfigPath(pathOrConfig, inputPath) {
   // require('tailwindcss')({ theme: ..., variants: ... })
   if (isObject(pathOrConfig) && pathOrConfig.config === undefined && !isEmpty(pathOrConfig)) {
     return null
@@ -25,7 +61,7 @@ export default function resolveConfigPath(pathOrConfig) {
     pathOrConfig.config !== undefined &&
     isString(pathOrConfig.config)
   ) {
-    return path.resolve(pathOrConfig.config)
+    return pickResolvedPath(pathOrConfig.config, inputPath)
   }
 
   // require('tailwindcss')({ config: { theme: ..., variants: ... } })
@@ -39,13 +75,13 @@ export default function resolveConfigPath(pathOrConfig) {
 
   // require('tailwindcss')('custom-config.js')
   if (isString(pathOrConfig)) {
-    return path.resolve(pathOrConfig)
+    return pickResolvedPath(pathOrConfig, inputPath)
   }
 
   // require('tailwindcss')
   for (const configFile of ['./tailwind.config.js', './tailwind.config.cjs']) {
     try {
-      const configPath = path.resolve(configFile)
+      const configPath = pickResolvedPath(configFile, inputPath)
       fs.accessSync(configPath)
       return configPath
     } catch (err) {}