Detect indent size from content

package.json

@@ -93,6 +93,7 @@
     "cross-env": "^7.0.0",
     "csrf": "^3.1.0",
     "date-fns": "^2.0.0",
+    "detect-indent": "^6.0.0",
     "diff": "^4.0.1",
     "elasticsearch": "^16.0.0",
     "entities": "^2.0.0",

src/client/js/components/PageEditor.jsx

@@ -1,6 +1,7 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 import loggerFactory from '@alias/logger';
+import detectIndent from 'detect-indent';
 
 import { throttle, debounce } from 'throttle-debounce';
 import { envUtils } from 'growi-commons';
@@ -59,6 +60,14 @@ class PageEditor extends React.Component {
       this.setState({ markdown: value });
     }));
     this.saveDraftWithDebounce = debounce(800, this.saveDraft);
+
+    // Detect indent size from contents (only when users are allowed to change it)
+    if (!this.props.appContainer.config.isIndentSizeForced && this.state.markdown) {
+      const detectedIndent = detectIndent(this.state.markdown);
+      if (detectedIndent.type === 'space' && new Set([2, 4]).has(detectedIndent.amount)) {
+        this.props.editorContainer.setState({ indentSize: detectedIndent.amount });
+      }
+    }
   }
 
   componentWillMount() {

yarn.lock

@@ -4938,6 +4938,11 @@ detect-indent@^5.0.0:
   resolved "https://registry.yarnpkg.com/detect-indent/-/detect-indent-5.0.0.tgz#3871cc0a6a002e8c3e5b3cf7f336264675f06b9d"
   integrity sha1-OHHMCmoALow+Wzz38zYmRnXwa50=
 
+detect-indent@^6.0.0:
+  version "6.0.0"
+  resolved "https://registry.yarnpkg.com/detect-indent/-/detect-indent-6.0.0.tgz#0abd0f549f69fc6659a254fe96786186b6f528fd"
+  integrity sha512-oSyFlqaTHCItVRGK5RmrmjB+CmaMOW7IaNA/kdxqhoa6d17j/5ce9O9eWXmV/KEdRwqpQA+Vqe8a8Bsybu4YnA==
+
 detect-libc@^1.0.2:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/detect-libc/-/detect-libc-1.0.3.tgz#fa137c4bd698edf55cd5cd02ac559f91a4c4ba9b"