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node_modules/eslint-plugin-react/lib/rules/no-unused-class-component-methods.js

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+/**
+ * @fileoverview Prevent declaring unused methods and properties of component class
+ * @author Paweł Nowak, Berton Zhu
+ */
+
+'use strict';
+
+const docsUrl = require('../util/docsUrl');
+const componentUtil = require('../util/componentUtil');
+const report = require('../util/report');
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+const LIFECYCLE_METHODS = new Set([
+  'constructor',
+  'componentDidCatch',
+  'componentDidMount',
+  'componentDidUpdate',
+  'componentWillMount',
+  'componentWillReceiveProps',
+  'componentWillUnmount',
+  'componentWillUpdate',
+  'getChildContext',
+  'getSnapshotBeforeUpdate',
+  'render',
+  'shouldComponentUpdate',
+  'UNSAFE_componentWillMount',
+  'UNSAFE_componentWillReceiveProps',
+  'UNSAFE_componentWillUpdate',
+]);
+
+const ES6_LIFECYCLE = new Set([
+  'state',
+]);
+
+const ES5_LIFECYCLE = new Set([
+  'getInitialState',
+  'getDefaultProps',
+  'mixins',
+]);
+
+function isKeyLiteralLike(node, property) {
+  return property.type === 'Literal'
+     || (property.type === 'TemplateLiteral' && property.expressions.length === 0)
+     || (node.computed === false && property.type === 'Identifier');
+}
+
+// Descend through all wrapping TypeCastExpressions and return the expression
+// that was cast.
+function uncast(node) {
+  while (node.type === 'TypeCastExpression') {
+    node = node.expression;
+  }
+  return node;
+}
+
+// Return the name of an identifier or the string value of a literal. Useful
+// anywhere that a literal may be used as a key (e.g., member expressions,
+// method definitions, ObjectExpression property keys).
+function getName(node) {
+  node = uncast(node);
+  const type = node.type;
+
+  if (type === 'Identifier') {
+    return node.name;
+  }
+  if (type === 'Literal') {
+    return String(node.value);
+  }
+  if (type === 'TemplateLiteral' && node.expressions.length === 0) {
+    return node.quasis[0].value.raw;
+  }
+  return null;
+}
+
+function isThisExpression(node) {
+  return uncast(node).type === 'ThisExpression';
+}
+
+function getInitialClassInfo(node, isClass) {
+  return {
+    classNode: node,
+    isClass,
+    // Set of nodes where properties were defined.
+    properties: new Set(),
+
+    // Set of names of properties that we've seen used.
+    usedProperties: new Set(),
+
+    inStatic: false,
+  };
+}
+
+const messages = {
+  unused: 'Unused method or property "{{name}}"',
+  unusedWithClass: 'Unused method or property "{{name}}" of class "{{className}}"',
+};
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  meta: {
+    docs: {
+      description: 'Disallow declaring unused methods of component class',
+      category: 'Best Practices',
+      recommended: false,
+      url: docsUrl('no-unused-class-component-methods'),
+    },
+    messages,
+    schema: [],
+  },
+
+  create: ((context) => {
+    let classInfo = null;
+
+    // Takes an ObjectExpression node and adds all named Property nodes to the
+    // current set of properties.
+    function addProperty(node) {
+      classInfo.properties.add(node);
+    }
+
+    // Adds the name of the given node as a used property if the node is an
+    // Identifier or a Literal. Other node types are ignored.
+    function addUsedProperty(node) {
+      const name = getName(node);
+      if (name) {
+        classInfo.usedProperties.add(name);
+      }
+    }
+
+    function reportUnusedProperties() {
+      // Report all unused properties.
+      for (const node of classInfo.properties) { // eslint-disable-line no-restricted-syntax
+        const name = getName(node);
+        if (
+          !classInfo.usedProperties.has(name)
+           && !LIFECYCLE_METHODS.has(name)
+           && (classInfo.isClass ? !ES6_LIFECYCLE.has(name) : !ES5_LIFECYCLE.has(name))
+        ) {
+          const className = (classInfo.classNode.id && classInfo.classNode.id.name) || '';
+
+          const messageID = className ? 'unusedWithClass' : 'unused';
+          report(
+            context,
+            messages[messageID],
+            messageID,
+            {
+              node,
+              data: {
+                name,
+                className,
+              },
+            }
+          );
+        }
+      }
+    }
+
+    function exitMethod() {
+      if (!classInfo || !classInfo.inStatic) {
+        return;
+      }
+
+      classInfo.inStatic = false;
+    }
+
+    return {
+      ClassDeclaration(node) {
+        if (componentUtil.isES6Component(node, context)) {
+          classInfo = getInitialClassInfo(node, true);
+        }
+      },
+
+      ObjectExpression(node) {
+        if (componentUtil.isES5Component(node, context)) {
+          classInfo = getInitialClassInfo(node, false);
+        }
+      },
+
+      'ClassDeclaration:exit'() {
+        if (!classInfo) {
+          return;
+        }
+        reportUnusedProperties();
+        classInfo = null;
+      },
+
+      'ObjectExpression:exit'(node) {
+        if (!classInfo || classInfo.classNode !== node) {
+          return;
+        }
+        reportUnusedProperties();
+        classInfo = null;
+      },
+
+      Property(node) {
+        if (!classInfo || classInfo.classNode !== node.parent) {
+          return;
+        }
+
+        if (isKeyLiteralLike(node, node.key)) {
+          addProperty(node.key);
+        }
+      },
+
+      'ClassProperty, MethodDefinition, PropertyDefinition'(node) {
+        if (!classInfo) {
+          return;
+        }
+
+        if (node.static) {
+          classInfo.inStatic = true;
+          return;
+        }
+
+        if (isKeyLiteralLike(node, node.key)) {
+          addProperty(node.key);
+        }
+      },
+
+      'ClassProperty:exit': exitMethod,
+      'MethodDefinition:exit': exitMethod,
+      'PropertyDefinition:exit': exitMethod,
+
+      MemberExpression(node) {
+        if (!classInfo || classInfo.inStatic) {
+          return;
+        }
+
+        if (isThisExpression(node.object) && isKeyLiteralLike(node, node.property)) {
+          if (node.parent.type === 'AssignmentExpression' && node.parent.left === node) {
+            // detect `this.property = xxx`
+            addProperty(node.property);
+          } else {
+            // detect `this.property()`, `x = this.property`, etc.
+            addUsedProperty(node.property);
+          }
+        }
+      },
+
+      VariableDeclarator(node) {
+        if (!classInfo || classInfo.inStatic) {
+          return;
+        }
+
+        // detect `{ foo, bar: baz } = this`
+        if (node.init && isThisExpression(node.init) && node.id.type === 'ObjectPattern') {
+          node.id.properties
+            .filter((prop) => prop.type === 'Property' && isKeyLiteralLike(prop, prop.key))
+            .forEach((prop) => {
+              addUsedProperty('key' in prop ? prop.key : undefined);
+            });
+        }
+      },
+    };
+  }),
+};