feat: allow assignment of check() return value (#785)

* Allow simple assignment statements in check() calls

* Documentation

Author: edemaine

docs/rules/audit-argument-checks.md

@@ -41,14 +41,26 @@ Meteor.methods({
   }
 })
 
+Meteor.methods({
+  foo: function (bar) {
+    var ret;
+    ret = check(bar, Match.Any)
+  }
+})
+
 ```
 
+For a check function to be considered "called", it must be called at the
+top level of the method or publish function (not e.g. within an `if` block),
+either as a lone expression statement or as an assignment statement where the
+right-hand side is just the function call (as in the last example above).
+
 ### Options
 
 If you define your own functions that call `check`, you can provide a list of
 such functions via the configuration `checkEquivalents`.  This rule assumes
 that these functions effectively check their first argument (an identifier or
-a list of identifiers).
+an array of identifiers).
 
 For example, in `.eslintrc.json`, you can specify the following configuration:
 

lib/rules/audit-argument-checks.js

@@ -52,6 +52,16 @@ module.exports = {
       }
 
       const checkedParams = [];
+      function processCheckArgs(args) {
+        if (args.length > 0 && args[0].type === 'Identifier') {
+          checkedParams.push(args[0].name);
+        }
+        if (args.length > 0 && args[0].type === 'ArrayExpression') {
+          args[0].elements.forEach((element) => {
+            if (element.type === 'Identifier') checkedParams.push(element.name);
+          });
+        }
+      }
 
       // short-circuit
       if (node.params.length === 0) {
@@ -64,24 +74,17 @@ module.exports = {
             expression.type === 'ExpressionStatement' &&
             expression.expression.type === 'CallExpression' &&
             expression.expression.callee.type === 'Identifier' &&
-            isCheck(expression.expression) &&
-            expression.expression.arguments.length > 0 &&
-            expression.expression.arguments[0].type === 'Identifier'
+            isCheck(expression.expression)
           ) {
-            checkedParams.push(expression.expression.arguments[0].name);
-          }
-          if (
+            processCheckArgs(expression.expression.arguments);
+          } else if (
             expression.type === 'ExpressionStatement' &&
-            expression.expression.type === 'CallExpression' &&
-            expression.expression.callee.type === 'Identifier' &&
-            isCheck(expression.expression) &&
-            expression.expression.arguments.length > 0 &&
-            expression.expression.arguments[0].type === 'ArrayExpression'
+            expression.expression.type === 'AssignmentExpression' &&
+            expression.expression.right.type === 'CallExpression' &&
+            expression.expression.right.callee.type === 'Identifier' &&
+            isCheck(expression.expression.right)
           ) {
-            expression.expression.arguments[0].elements.forEach((element) => {
-              if (element.type === 'Identifier')
-                checkedParams.push(element.name);
-            });
+            processCheckArgs(expression.expression.right.arguments);
           }
         });
       }

tests/lib/rules/audit-argument-checks.js

@@ -42,6 +42,15 @@ ruleTester.run('audit-argument-checks', rule, {
       code: 'Meteor.publish("foo", function (bar) { checkId(bar); })',
       options: [{ checkEquivalents: ['checkId'] }],
     },
+    {
+      code:
+        'Meteor.publish("foo", function (bar) { var r; r = checkId(bar); })',
+      options: [{ checkEquivalents: ['checkId'] }],
+    },
+    {
+      code: 'Meteor.publish("foo", function () { checkId(); })',
+      options: [{ checkEquivalents: ['checkId'] }],
+    },
 
     'Meteor.methods()',
     'Meteor.methods({ x: function () {} })',