[Fix]: improve algorithm to check if a variable is coming from the pr…

…agma

lib/util/Components.js

@@ -307,8 +307,63 @@ function componentRule(rule, context) {
       const variables = variableUtil.variablesInScope(context);
       const variableInScope = variableUtil.getVariable(variables, variable);
       if (variableInScope) {
-        const map = variableInScope.scope.set;
-        return map.has(pragma);
+        const latestDef = variableUtil.getLatestVariableDefinition(variableInScope);
+        if (latestDef) {
+          // check if latest definition is a variable declaration: 'variable = value'
+          if (latestDef.node.type === 'VariableDeclarator' && latestDef.node.init) {
+            // check for: 'variable = pragma.variable'
+            if (
+              latestDef.node.init.type === 'MemberExpression'
+              && latestDef.node.init.object.type === 'Identifier'
+              && latestDef.node.init.object.name === pragma
+            ) {
+              return true;
+            }
+            // check for: '{variable} = pragma'
+            if (
+              latestDef.node.init.type === 'Identifier'
+              && latestDef.node.init.name === pragma
+            ) {
+              return true;
+            }
+
+            // "require('react')"
+            let requireExpression = null;
+
+            // get "require('react')" from: "{variable} = require('react')"
+            if (latestDef.node.init.type === 'CallExpression') {
+              requireExpression = latestDef.node.init;
+            }
+            // get "require('react')" from: "variable = require('react').variable"
+            if (
+              !requireExpression
+              && latestDef.node.init.type === 'MemberExpression'
+              && latestDef.node.init.object.type === 'CallExpression'
+            ) {
+              requireExpression = latestDef.node.init.object;
+            }
+
+            // check proper require.
+            if (
+              requireExpression.callee.name === 'require'
+              && requireExpression.arguments[0]
+              && requireExpression.arguments[0].value === pragma.toLocaleLowerCase()
+            ) {
+              return true;
+            }
+
+            return false;
+          }
+
+          // latest definition is an import declaration: import {<variable>} from 'react'
+          if (
+            latestDef.parent
+            && latestDef.parent.type === 'ImportDeclaration'
+            && latestDef.parent.source.value === pragma.toLocaleLowerCase()
+          ) {
+            return true;
+          }
+        }
       }
       return false;
     },

lib/util/variable.js

@@ -72,9 +72,19 @@ function findVariableByName(context, name) {
   return variable.defs[0].node.init;
 }
 
+/**
+ * Returns the latest definition of the variable.
+ * @param {Object} variable
+ * @returns {Object | undefined} The latest variable definition or undefined.
+ */
+function getLatestVariableDefinition(variable) {
+  return variable.defs[variable.defs.length - 1];
+}
+
 module.exports = {
   findVariable,
   findVariableByName,
   getVariable,
-  variablesInScope
+  variablesInScope,
+  getLatestVariableDefinition
 };

tests/lib/rules/no-multi-comp.js

@@ -221,6 +221,25 @@ ruleTester.run('no-multi-comp', rule, {
     options: [{
       ignoreStateless: false
     }]
+  }, {
+    code: `
+      import React from 'react';
+      function memo() {
+        var outOfScope = "hello"
+        return null;
+      }
+      class ComponentY extends React.Component {
+        memoCities = memo((cities) => cities.map((v) => ({ label: v })));
+        render() {
+          return (
+            <div>
+              <div>Counter</div>
+            </div>
+          );
+        }
+      }
+    `,
+    parser: parsers.BABEL_ESLINT
   }],
 
   invalid: [{
@@ -376,5 +395,171 @@ ruleTester.run('no-multi-comp', rule, {
       message: 'Declare only one React component per file',
       line: 5
     }]
+  }, {
+    code: `
+      const forwardRef = React.forwardRef;
+      const HelloComponent = (0, (props) => {
+        return <div></div>;
+      });
+      const HelloComponent2 = forwardRef((props, ref) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+      const memo = React.memo;
+      const HelloComponent = (props) => {
+        return <div></div>;
+      };
+      const HelloComponent2 = memo((props) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+      const {forwardRef} = React;
+      const HelloComponent = (0, (props) => {
+        return <div></div>;
+      });
+      const HelloComponent2 = forwardRef((props, ref) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+      const {memo} = React;
+      const HelloComponent = (0, (props) => {
+        return <div></div>;
+      });
+      const HelloComponent2 = memo((props) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+      import React, { memo } from 'react';
+      const HelloComponent = (0, (props) => {
+        return <div></div>;
+      });
+      const HelloComponent2 = memo((props) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+      import {forwardRef} from 'react';
+      const HelloComponent = (0, (props) => {
+        return <div></div>;
+      });
+      const HelloComponent2 = forwardRef((props, ref) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+      const { memo } = require('react');
+      const HelloComponent = (0, (props) => {
+        return <div></div>;
+      });
+      const HelloComponent2 = memo((props) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+      const {forwardRef} = require('react');
+      const HelloComponent = (0, (props) => {
+        return <div></div>;
+      });
+      const HelloComponent2 = forwardRef((props, ref) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+      const forwardRef = require('react').forwardRef;
+      const HelloComponent = (0, (props) => {
+        return <div></div>;
+      });
+      const HelloComponent2 = forwardRef((props, ref) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+      const memo = require('react').memo;
+      const HelloComponent = (0, (props) => {
+        return <div></div>;
+      });
+      const HelloComponent2 = memo((props) => <HelloComponent></HelloComponent>);
+    `,
+    options: [{
+      ignoreStateless: false
+    }],
+    errors: [{
+      message: 'Declare only one React component per file',
+      line: 6
+    }]
+  }, {
+    code: `
+        import Foo, { memo, forwardRef } from 'foo';
+        const Text = forwardRef(({ text }, ref) => {
+          return <div ref={ref}>{text}</div>;
+        })
+        const Label = memo(() => <Text />);
+      `,
+    settings: {
+      react: {
+        pragma: 'Foo'
+      }
+    },
+    errors: [{
+      message: 'Declare only one React component per file'
+    }]
   }]
 });

tests/util/variable.js

@@ -0,0 +1,27 @@
+'use strict';
+
+const assert = require('assert');
+
+const getLatestVariableDefinition = require('../../lib/util/variable').getLatestVariableDefinition;
+
+describe('variable', () => {
+  describe('getLatestVariableDefinition', () => {
+    it('should return undefined for empty definitions', () => {
+      const variable = {
+        defs: []
+      };
+      assert.equal(getLatestVariableDefinition(variable), undefined);
+    });
+
+    it('should return the latest definition', () => {
+      const variable = {
+        defs: [
+          'one',
+          'two',
+          'latest'
+        ]
+      };
+      assert.equal(getLatestVariableDefinition(variable), 'latest');
+    });
+  });
+});