From 0e8a14149058bdb8b88d14771afb0f0c42cea62d Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Fri, 30 May 2025 22:45:59 +0200
Subject: [PATCH] Add custom eslint rule: no-placeholder-comments

---
 eslint-rules/README.md                  | 49 +++++++++++++++++++++++++
 eslint-rules/index.js                   |  7 ++++
 eslint-rules/no-placeholder-comments.js | 45 +++++++++++++++++++++++
 eslint.config.js                        |  3 ++
 4 files changed, 104 insertions(+)
 create mode 100644 eslint-rules/README.md
 create mode 100644 eslint-rules/index.js
 create mode 100644 eslint-rules/no-placeholder-comments.js

diff --git a/eslint-rules/README.md b/eslint-rules/README.md
new file mode 100644
index 0000000..7c882dd
--- /dev/null
+++ b/eslint-rules/README.md
@@ -0,0 +1,49 @@
+# Custom ESLint Rules
+
+This directory contains custom ESLint rules for the project.
+
+## no-placeholder-comments
+
+This rule detects and flags comments that start with "// In a real" (case-insensitive). These comments typically indicate placeholder implementations that should be replaced with real code.
+
+### Examples
+
+❌ **Bad** - These will trigger the rule:
+```javascript
+// In a real application, this would connect to a database
+const data = [];
+
+// in a real world scenario, this would be different
+const config = {};
+
+/* In a real implementation, we would handle errors */
+const handleError = () => {};
+```
+
+✅ **Good** - These are fine:
+```javascript
+// This is a regular comment
+const data = [];
+
+// TODO: Implement database connection
+const config = {};
+
+// Note: In a real application, consider using a database
+const handleError = () => {};
+```
+
+### Configuration
+
+The rule is configured in `eslint.config.js` as:
+```javascript
+"custom/no-placeholder-comments": "error"
+```
+
+You can change the severity level to:
+- `"off"` - Disable the rule
+- `"warn"` - Show as warning
+- `"error"` - Show as error (current setting)
+
+### Purpose
+
+This rule helps ensure that placeholder comments used during development are replaced with actual implementations before code is committed or deployed to production.
\ No newline at end of file
diff --git a/eslint-rules/index.js b/eslint-rules/index.js
new file mode 100644
index 0000000..7569a01
--- /dev/null
+++ b/eslint-rules/index.js
@@ -0,0 +1,7 @@
+import noPlaceholderComments from './no-placeholder-comments.js';
+
+export default {
+  rules: {
+    'no-placeholder-comments': noPlaceholderComments,
+  },
+};
\ No newline at end of file
diff --git a/eslint-rules/no-placeholder-comments.js b/eslint-rules/no-placeholder-comments.js
new file mode 100644
index 0000000..b2f7b95
--- /dev/null
+++ b/eslint-rules/no-placeholder-comments.js
@@ -0,0 +1,45 @@
+/**
+ * Custom ESLint rule to detect placeholder comments starting with "// In a real"
+ * These comments indicate incomplete implementations that should be replaced with real code.
+ */
+
+export default {
+  meta: {
+    type: "problem",
+    docs: {
+      description: "Disallow placeholder comments starting with '// In a real'",
+      category: "Best Practices",
+      recommended: true,
+    },
+    fixable: null,
+    schema: [],
+    messages: {
+      placeholderComment: "Placeholder comment detected: '{{comment}}'. This should be replaced with a real implementation.",
+    },
+  },
+
+  create(context) {
+    const sourceCode = context.getSourceCode();
+
+    return {
+      Program() {
+        const comments = sourceCode.getAllComments();
+        
+        comments.forEach((comment) => {
+          const commentText = comment.value.trim();
+          
+          // Check if comment starts with "In a real" (case-insensitive)
+          if (commentText.toLowerCase().startsWith("in a real")) {
+            context.report({
+              node: comment,
+              messageId: "placeholderComment",
+              data: {
+                comment: `// ${commentText}`,
+              },
+            });
+          }
+        });
+      },
+    };
+  },
+};
\ No newline at end of file
diff --git a/eslint.config.js b/eslint.config.js
index e67846f..0434c3a 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -3,6 +3,7 @@ import globals from "globals";
 import reactHooks from "eslint-plugin-react-hooks";
 import reactRefresh from "eslint-plugin-react-refresh";
 import tseslint from "typescript-eslint";
+import customRules from "./eslint-rules/index.js";
 
 export default tseslint.config(
   { ignores: ["dist"] },
@@ -16,6 +17,7 @@ export default tseslint.config(
     plugins: {
       "react-hooks": reactHooks,
       "react-refresh": reactRefresh,
+      "custom": customRules,
     },
     rules: {
       ...reactHooks.configs.recommended.rules,
@@ -24,6 +26,7 @@ export default tseslint.config(
         { allowConstantExport: true },
       ],
       "@typescript-eslint/no-unused-vars": "off",
+      "custom/no-placeholder-comments": "error",
     },
   }
 );