Compute block scope declaration

eslint · Dec 27, 2018 · 0b3a3a4 · 0b3a3a4
1 parent 0772a0a
commit 0b3a3a4
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Showing 2 changed files with 36 additions and 34 deletions.
diff --git a/lib/rules/no-else-return.js b/lib/rules/no-else-return.js
@@ -16,15 +16,8 @@ const FixTracker = require("../util/fix-tracker");
 // Helpers
 //------------------------------------------------------------------------------
 
-/**
- * @param {Token} token - The token to check
- * @returns {boolean} `true` if keyword let or const exist
- */
-function isVariableDeclaration(token) {
-    const variableDeclaration = token.value === "let" || token.value === "const";
+const BLOCK_SCOPED_DECLARATION = /^(?:VariableDeclarator|ClassDeclaration)$/;
 
-    return token.type === "Keyword" && variableDeclaration;
-}
 
 //------------------------------------------------------------------------------
 // Rule Definition
@@ -104,31 +97,40 @@ module.exports = {
                     const endToken = sourceCode.getLastToken(node);
 
                     /**
-                     * If else block includes block scope local variable declaration [let or const],
-                     * then it is not safe to remove else keyword [issue 11069]
+                     * Dig into `else` branch and receive all root level declarations.
+                     * Checks only if @var foo is block scope declaration, @not @var x
+                     * @example
+                     *   function foo (){
+                     *      if(baz){
+                     *        return 42
+                     *      } else {
+                     *        let foo=1;
+                     *        {
+                     *          const x=10;
+                     *        }
+                     *        return foo
+                     *      }
+                     *   }
+                     *
                      */
-                    const isDeclarationInside = sourceCode.getTokensBetween(startToken, endToken).findIndex(isVariableDeclaration) > -1;
-
-                    const childScopeVars = (childScopes, store = {}, level = 0) =>
-                        childScopes.reduce((acc, block) => {
-                            if (block.childScopes.length >= 0) {
-                                acc[level] = block.variables;
-                                let index = level + 1
-                                return childScopeVars(block.childScopes, acc, index);
-                            }
-                            return acc
-                        }, store)
-
-                    const shadowedVariables = scope => {
-                        const result = childScopeVars(scope.childScopes);
-                        return scope.variables.filter(elem => result[0].findIndex(vars => vars.name === elem.name) > -1)
-                    };
-                    const shadowed = shadowedVariables(context.getScope());
-                    console.log('test', shadowed)
-
-                    if (isDeclarationInside) {
-                        return null;
-                    }
+                     const blockScopeDeclaration = scope => {
+                         return scope.childScopes.some(childScope => {
+                             const {
+                                 start,
+                                 end
+                             } = childScope.block;
+
+                             const elseBranch =
+                                 start === startToken.start && end === endToken.end;
+
+                             return elseBranch ? childScope.variables.some(variable => BLOCK_SCOPED_DECLARATION.test(variable.defs[0].node.type)) : false
+
+                         });
+                     };
+
+                     if (blockScopeDeclaration(context.getScope())) {
+                         return null;
+                     }
 
                     const lastTokenOfElseBlock = sourceCode.getTokenBefore(endToken);
 

diff --git a/tests/lib/rules/no-else-return.js b/tests/lib/rules/no-else-return.js
@@ -202,8 +202,8 @@ ruleTester.run("no-else-return", rule, {
             errors: [{ messageId: "unexpected", type: "BlockStatement" }]
         },
         {
-            code: "function foo() { let bar = true; if (baz) { return; } else { { let bar = false; }  return; } }",
-            output: null,
+            code: "function foo() { let bar = true; if (baz) { return baz; } else { { let bar = false; }  return bar; } }",
+            output: "function foo() { let bar = true; if (baz) { return baz; }  { let bar = false; }  return bar;  }",
             parserOptions: { ecmaVersion: 6 },
             errors: [
                 { messageId: "unexpected", type: "BlockStatement" }