Deprecate no-unused-variable rule (#1618)

Resolves #1481. Adds a `deprecationMessage` field to rule metadata.

src/configs/recommended.ts

@@ -68,7 +68,8 @@ export const rules = {
     "no-unreachable": true,
     "no-unused-expression": true,
     "no-unused-new": true,
-    "no-unused-variable": [true, "react"],
+    // deprecated as of v4.0
+    "no-unused-variable": false,
     // disable this rule as it is very heavy performance-wise and not that useful
     "no-use-before-declare": false,
     "no-var-keyword": true,

src/language/rule/rule.ts

@@ -30,6 +30,11 @@ export interface IRuleMetadata {
      */
     type: RuleType;
 
+    /**
+     * A rule deprecation message, if applicable.
+     */
+    deprecationMessage?: string;
+
     /**
      * A short, one line description of what the rule does.
      */

src/ruleLoader.ts

@@ -48,6 +48,10 @@ export function loadRules(ruleConfiguration: {[name: string]: any},
                 const ruleSpecificList = (ruleName in enableDisableRuleMap ? enableDisableRuleMap[ruleName] : []);
                 const disabledIntervals = buildDisabledIntervalsFromSwitches(ruleSpecificList, allList);
                 rules.push(new Rule(ruleName, ruleValue, disabledIntervals));
+
+                if (Rule.metadata && Rule.metadata.deprecationMessage) {
+                    console.warn(`${Rule.metadata.ruleName} is deprecated. ${Rule.metadata.deprecationMessage}`);
+                }
             }
         }
     }

src/rules/noUnusedVariableRule.ts

@@ -31,6 +31,7 @@ export class Rule extends Lint.Rules.AbstractRule {
     /* tslint:disable:object-literal-sort-keys */
     public static metadata: Lint.IRuleMetadata = {
         ruleName: "no-unused-variable",
+        deprecationMessage: "Use the compiler options --noUnusedParameters and --noUnusedLocals instead.",
         description: "Disallows unused imports, variables, functions and private class members.",
         optionsDescription: Lint.Utils.dedent`
             Three optional arguments may be optionally provided:
@@ -331,7 +332,7 @@ class NoUnusedVariablesWalker extends Lint.RuleWalker {
             node.modifiers,
             ts.SyntaxKind.PublicKeyword,
             ts.SyntaxKind.PrivateKeyword,
-            ts.SyntaxKind.ProtectedKeyword
+            ts.SyntaxKind.ProtectedKeyword,
         );
 
         if (!isSingleVariable && isPropertyParameter) {

src/tslintMulti.ts

@@ -132,25 +132,25 @@ class MultiLinter {
     }
 
     public getResult(): LintResult {
-      let formatter: IFormatter;
-      const formattersDirectory = getRelativePath(this.options.formattersDirectory);
-
-      const formatterName = this.options.formatter || "prose";
-      const Formatter = findFormatter(formatterName, formattersDirectory);
-      if (Formatter) {
-          formatter = new Formatter();
-      } else {
-          throw new Error(`formatter '${formatterName}' not found`);
-      }
-
-      const output = formatter.format(this.failures);
-
-      return {
-          failureCount: this.failures.length,
-          failures: this.failures,
-          format: formatterName,
-          output,
-      };
+        let formatter: IFormatter;
+        const formattersDirectory = getRelativePath(this.options.formattersDirectory);
+
+        const formatterName = this.options.formatter || "prose";
+        const Formatter = findFormatter(formatterName, formattersDirectory);
+        if (Formatter) {
+            formatter = new Formatter();
+        } else {
+            throw new Error(`formatter '${formatterName}' not found`);
+        }
+
+        const output = formatter.format(this.failures);
+
+        return {
+            failureCount: this.failures.length,
+            failures: this.failures,
+            format: formatterName,
+            output,
+        };
     }
 
     private containsRule(rules: RuleFailure[], rule: RuleFailure) {