tested plugin successfully. Tested with valid and invalid json, tested turning on and off plugin too. && git push

Author: MeepTech

main.ts

@@ -2,12 +2,14 @@ import { App, Plugin, PluginSettingTab, Setting } from 'obsidian';
 
 interface CustomFileExtensionsSettings {
   additionalFileTypes: string;
-  previousAdditionalFileTypes: string;
+  previousAdditionalFileTypes: object;
+  currentValueIsInvalidJson: boolean;
 }
 
 const DEFAULT_SETTINGS: CustomFileExtensionsSettings = {
-  additionalFileTypes: '{markdown: ["", "txt", "html", "js", "css", "ts", "yaml"]}',
-  previousAdditionalFileTypes: '{markdown: ["", "txt", "html", "js", "css", "ts", "yaml"]}'
+  additionalFileTypes: '{"markdown": ["", "txt", "html", "js", "css", "ts", "yaml"]}',
+  previousAdditionalFileTypes: { markdown: ["", "txt", "html", "js", "css", "ts", "yaml"] },
+  currentValueIsInvalidJson: false
 }
 
 export default class CustomFileExtensions extends Plugin {
@@ -17,7 +19,6 @@ export default class CustomFileExtensions extends Plugin {
     super.onload();
     await this.loadSettings();
     this.addSettingTab(new CustomFileExtensionsSettingTab(this.app, this));
-
     this.apply();
   }
 
@@ -31,24 +32,32 @@ export default class CustomFileExtensions extends Plugin {
 
 	async saveSettings() {
     await this.saveData(this.settings);
+    this.revert();
     this.apply();
   }
 
   apply() {
-    this.revert();
-
     // apply new types:
     const views = JSON.parse(this.settings.additionalFileTypes);
     for (const view in views) {
-      this.registerExtensions([views[view]], view);
+      for (const fileType of views[view]) {
+        this.registerExtensions([fileType], view);
+      }
     }
   }
 
   revert() {
-    for (const view in Object.values(this.plugin.settings.additionalFileTypes).flat()) {
-      this.registerExtensions(view, "");
+    for (const view of Object.values(this.settings.previousAdditionalFileTypes).flat()) {
+      try {
+        this.app.viewRegistry.unregisterExtensions([view]);
+      } catch {
+        console.log("ERROR");
+      }
     }
-    this.registerExtensions([".md"], 'markdown');
+
+    try {
+      this.registerExtensions([".md"], 'markdown');
+    } catch {}
   }
 }
 
@@ -72,11 +81,19 @@ class CustomFileExtensionsSettingTab extends PluginSettingTab {
 			.setDesc("Valid entry is a JSON object with properties named after the desired view, containing the file types to assign to that view. EX: " + DEFAULT_SETTINGS.additionalFileTypes)
 			.addText(text => text
 				.setPlaceholder(DEFAULT_SETTINGS.additionalFileTypes)
-				.setValue(this.plugin.settings.additionalFileTypes)
+        .setValue(this.plugin.settings.additionalFileTypes)
         .onChange(async (value) => {
+          try {
+            JSON.parse(value);
+            this.plugin.settings.currentValueIsInvalidJson = false;
+          } catch {
+            this.plugin.settings.currentValueIsInvalidJson = true;
+            return;
+          }
+
           this.plugin.settings.previousAdditionalFileTypes = JSON.parse(this.plugin.settings.additionalFileTypes);
 					this.plugin.settings.additionalFileTypes = value;
 					await this.plugin.saveSettings();
-				}));
+        }));
 	}
 }