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node_modules/eslint-plugin-react/lib/util/jsx.js

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+/**
+ * @fileoverview Utility functions for JSX
+ */
+
+'use strict';
+
+const elementType = require('jsx-ast-utils/elementType');
+
+const astUtil = require('./ast');
+const isCreateElement = require('./isCreateElement');
+const variableUtil = require('./variable');
+
+// See https://github.com/babel/babel/blob/ce420ba51c68591e057696ef43e028f41c6e04cd/packages/babel-types/src/validators/react/isCompatTag.js
+// for why we only test for the first character
+const COMPAT_TAG_REGEX = /^[a-z]/;
+
+/**
+ * Checks if a node represents a DOM element according to React.
+ * @param {object} node - JSXOpeningElement to check.
+ * @returns {boolean} Whether or not the node corresponds to a DOM element.
+ */
+function isDOMComponent(node) {
+  const name = elementType(node);
+  return COMPAT_TAG_REGEX.test(name);
+}
+
+/**
+ * Test whether a JSXElement is a fragment
+ * @param {JSXElement} node
+ * @param {string} reactPragma
+ * @param {string} fragmentPragma
+ * @returns {boolean}
+ */
+function isFragment(node, reactPragma, fragmentPragma) {
+  const name = node.openingElement.name;
+
+  // <Fragment>
+  if (name.type === 'JSXIdentifier' && name.name === fragmentPragma) {
+    return true;
+  }
+
+  // <React.Fragment>
+  if (
+    name.type === 'JSXMemberExpression'
+    && name.object.type === 'JSXIdentifier'
+    && name.object.name === reactPragma
+    && name.property.type === 'JSXIdentifier'
+    && name.property.name === fragmentPragma
+  ) {
+    return true;
+  }
+
+  return false;
+}
+
+/**
+ * Checks if a node represents a JSX element or fragment.
+ * @param {object} node - node to check.
+ * @returns {boolean} Whether or not the node if a JSX element or fragment.
+ */
+function isJSX(node) {
+  return node && ['JSXElement', 'JSXFragment'].indexOf(node.type) >= 0;
+}
+
+/**
+ * Check if node is like `key={...}` as in `<Foo key={...} />`
+ * @param {ASTNode} node
+ * @returns {boolean}
+ */
+function isJSXAttributeKey(node) {
+  return node.type === 'JSXAttribute'
+    && node.name
+    && node.name.type === 'JSXIdentifier'
+    && node.name.name === 'key';
+}
+
+/**
+ * Check if value has only whitespaces
+ * @param {unknown} value
+ * @returns {boolean}
+ */
+function isWhiteSpaces(value) {
+  return typeof value === 'string' ? /^\s*$/.test(value) : false;
+}
+
+/**
+ * Check if the node is returning JSX or null
+ *
+ * @param {Context} context The context of `ASTNode`.
+ * @param {ASTNode} ASTnode The AST node being checked
+ * @param {boolean} [strict] If true, in a ternary condition the node must return JSX in both cases
+ * @param {boolean} [ignoreNull] If true, null return values will be ignored
+ * @returns {boolean} True if the node is returning JSX or null, false if not
+ */
+function isReturningJSX(context, ASTnode, strict, ignoreNull) {
+  const isJSXValue = (node) => {
+    if (!node) {
+      return false;
+    }
+    switch (node.type) {
+      case 'ConditionalExpression':
+        if (strict) {
+          return isJSXValue(node.consequent) && isJSXValue(node.alternate);
+        }
+        return isJSXValue(node.consequent) || isJSXValue(node.alternate);
+      case 'LogicalExpression':
+        if (strict) {
+          return isJSXValue(node.left) && isJSXValue(node.right);
+        }
+        return isJSXValue(node.left) || isJSXValue(node.right);
+      case 'SequenceExpression':
+        return isJSXValue(node.expressions[node.expressions.length - 1]);
+      case 'JSXElement':
+      case 'JSXFragment':
+        return true;
+      case 'CallExpression':
+        return isCreateElement(context, node);
+      case 'Literal':
+        if (!ignoreNull && node.value === null) {
+          return true;
+        }
+        return false;
+      case 'Identifier': {
+        const variable = variableUtil.findVariableByName(context, node, node.name);
+        return isJSX(variable);
+      }
+      default:
+        return false;
+    }
+  };
+
+  let found = false;
+  astUtil.traverseReturns(ASTnode, context, (node, breakTraverse) => {
+    if (isJSXValue(node)) {
+      found = true;
+      breakTraverse();
+    }
+  });
+
+  return found;
+}
+
+/**
+ * Check if the node is returning only null values
+ *
+ * @param {ASTNode} ASTnode The AST node being checked
+ * @param {Context} context The context of `ASTNode`.
+ * @returns {boolean} True if the node is returning only null values
+ */
+function isReturningOnlyNull(ASTnode, context) {
+  let found = false;
+  let foundSomethingElse = false;
+  astUtil.traverseReturns(ASTnode, context, (node) => {
+    // Traverse return statement
+    astUtil.traverse(node, {
+      enter(childNode) {
+        const setFound = () => {
+          found = true;
+          this.skip();
+        };
+        const setFoundSomethingElse = () => {
+          foundSomethingElse = true;
+          this.skip();
+        };
+        switch (childNode.type) {
+          case 'ReturnStatement':
+            break;
+          case 'ConditionalExpression':
+            if (childNode.consequent.value === null && childNode.alternate.value === null) {
+              setFound();
+            }
+            break;
+          case 'Literal':
+            if (childNode.value === null) {
+              setFound();
+            }
+            break;
+          default:
+            setFoundSomethingElse();
+        }
+      },
+    });
+  });
+
+  return found && !foundSomethingElse;
+}
+
+module.exports = {
+  isDOMComponent,
+  isFragment,
+  isJSX,
+  isJSXAttributeKey,
+  isWhiteSpaces,
+  isReturningJSX,
+  isReturningOnlyNull,
+};