Don't try to create a regex from a regex, use better regex detection

.yarnrc.yml

@@ -0,0 +1 @@
+nodeLinker: node-modules

README.md

@@ -519,6 +519,8 @@ If you are using a configuration file, and you want to use a regular expression
 }
 ```
 
+It is not necessary to use the `--isRegex` flag in this case.
+
 ## A note on using globs with the CLI
 When using the CLI, the glob pattern is handled by the operating system. But if you specify the glob pattern in the configuration file, the package will use the glob module from the Node modules, and this can lead to different behaviour despite using the same pattern.
 

bin/cli.js

@@ -33,7 +33,7 @@ async function main() {
   }, [])
 
   //If the isRegex flag is passed, convert the from parameter to a RegExp object
-  if (isRegex) {
+  if (isRegex && typeof from === 'string') {
     const flags = from.replace(/.*\/([gimyus]*)$/, '$1')
     const pattern = from.replace(new RegExp(`^/(.*?)/${flags}$`), '$1')
     options.from = new RegExp(pattern, flags)

package.json

@@ -1,7 +1,7 @@
 {
   "name": "replace-in-file",
   "type": "module",
-  "version": "8.0.1",
+  "version": "8.0.2",
   "description": "A simple utility to quickly replace text in one or more files.",
   "homepage": "https://github.com/adamreisnz/replace-in-file#readme",
   "author": {

src/helpers/config.js

@@ -17,7 +17,7 @@ export async function loadConfig(file) {
   const config = JSON.parse(json)
 
   //Since we can't store Regexp in JSON, convert from string if needed
-  if (config.from && config.from.startsWith('/')) {
+  if (config.from && config.from.match(/.*\/([gimyus]*)$/)) {
     config.from = new RegExp(config.from)
   }
 

src/helpers/config.spec.js

@@ -70,7 +70,7 @@ describe('helpers/config.js', () => {
       //Test config
       const config = {
         files: ['file.txt'],
-        from: 'foo',
+        from: '/foo',
         to: 'bar',
       }
       fs.writeFileSync('config.json', JSON.stringify(config), 'utf8')
@@ -83,6 +83,25 @@ describe('helpers/config.js', () => {
       //Clean up
       fs.unlinkSync('config.json')
     })
+
+    it('should ignore the isRegex flag if a regex has already been provided', async () => {
+
+      //Test config
+      const config = {
+        files: ['file.txt'],
+        from: '/foo/g',
+        to: 'bar',
+        isRegex: true,
+      }
+      fs.writeFileSync('config.json', JSON.stringify(config), 'utf8')
+
+      //Load config
+      const cfg = await loadConfig('config.json')
+      expect(cfg.from).to.be.an.instanceof(RegExp)
+
+      //Clean up
+      fs.unlinkSync('config.json')
+    })
   })
 
   /**