Update: Suggest missing rule in flat config (fixes #14027)

lib/config/rule-validator.js

@@ -35,16 +35,33 @@ function findRuleDefinition(ruleId, config) {
         pluginName = ruleIdParts.join("/");
     }
 
-    if (!config.plugins || !config.plugins[pluginName]) {
-        throw new TypeError(`Key "rules": Key "${ruleId}": Could not find plugin "${pluginName}".`);
-    }
+    const errorMessageHeader = `Key "rules": Key "${ruleId}"`;
+    let errorMessage = `${errorMessageHeader}: Could not find plugin "${pluginName}".`;
 
-    if (!config.plugins[pluginName].rules || !config.plugins[pluginName].rules[ruleName]) {
-        throw new TypeError(`Key "rules": Key "${ruleId}": Could not find "${ruleName}" in plugin "${pluginName}".`);
-    }
+    // if the plugin exists then we need to check if the rule exists
+    if (config.plugins && config.plugins[pluginName]) {
+
+        const plugin = config.plugins[pluginName];
+
+        // first check for exact rule match
+        if (plugin.rules && plugin.rules[ruleName]) {
+            return config.plugins[pluginName].rules[ruleName];
+        }
 
-    return config.plugins[pluginName].rules[ruleName];
+        errorMessage = `${errorMessageHeader}: Could not find "${ruleName}" in plugin "${pluginName}".`;
+
+        // otherwise, let's see if we can find the rule name elsewhere
+        for (const [otherPluginName, otherPlugin] of Object.entries(config.plugins)) {
+            if (otherPlugin.rules && otherPlugin.rules[ruleName]) {
+                errorMessage += ` Did you mean "${otherPluginName}/${ruleName}"?`;
+                break;
+            }
+        }
+
+        // falls through to throw error
+    }
 
+    throw new TypeError(errorMessage);
 }
 
 /**

tests/lib/config/flat-config-array.js

@@ -56,6 +56,16 @@ const baseConfig = {
                     }
                 }
             }
+        },
+        test1: {
+            rules: {
+                match: {}
+            }
+        },
+        test2: {
+            rules: {
+                nomatch: {}
+            }
         }
     }
 };
@@ -1278,6 +1288,39 @@ describe("FlatConfigArray", () => {
                 ], "Key \"rules\": Key \"foo\": Expected severity of \"off\", 0, \"warn\", 1, \"error\", or 2.");
             });
 
+            it("should error when rule doesn't exist", async () => {
+
+                await assertInvalidConfig([
+                    {
+                        rules: {
+                            foox: [1, "bar"]
+                        }
+                    }
+                ], /Key "rules": Key "foox": Could not find "foox" in plugin "@"./u);
+            });
+
+            it("should error and suggest alternative when rule doesn't exist", async () => {
+
+                await assertInvalidConfig([
+                    {
+                        rules: {
+                            "test2/match": "error"
+                        }
+                    }
+                ], /Key "rules": Key "test2\/match": Could not find "match" in plugin "test2"\. Did you mean "test1\/match"\?/u);
+            });
+
+            it("should error when plugin for rule doesn't exist", async () => {
+
+                await assertInvalidConfig([
+                    {
+                        rules: {
+                            "doesnt-exist/match": "error"
+                        }
+                    }
+                ], /Key "rules": Key "doesnt-exist\/match": Could not find plugin "doesnt-exist"\./u);
+            });
+
             it("should error when rule options don't match schema", async () => {
 
                 await assertInvalidConfig([