fix(scope-manager): don't create references for intrinsic JSX elements (

#2504)

packages/eslint-plugin/tests/eslint-rules/no-undef.test.ts

@@ -199,6 +199,27 @@ function Foo() {}
         },
       },
     },
+    // intrinsic elements should not cause errors
+    {
+      code: `
+<div />;
+      `,
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+      },
+    },
+    {
+      code: `
+<span></span>;
+      `,
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+      },
+    },
     // https://github.com/typescript-eslint/typescript-eslint/issues/2477
     `
 const x = 1 as const;

packages/scope-manager/src/referencer/Referencer.ts

@@ -558,6 +558,10 @@ class Referencer extends Visitor {
     this.visit(node.value);
   }
 
+  protected JSXClosingElement(): void {
+    // should not be counted as a reference
+  }
+
   protected JSXFragment(node: TSESTree.JSXFragment): void {
     this.referenceJsxPragma();
     this.referenceJsxFragment();
@@ -575,7 +579,16 @@ class Referencer extends Visitor {
 
   protected JSXOpeningElement(node: TSESTree.JSXOpeningElement): void {
     this.referenceJsxPragma();
-    this.visit(node.name);
+    if (node.name.type === AST_NODE_TYPES.JSXIdentifier) {
+      if (node.name.name[0].toUpperCase() === node.name.name[0]) {
+        // lower cased component names are always treated as "intrinsic" names, and are converted to a string,
+        // not a variable by JSX transforms:
+        // <div /> => React.createElement("div", null)
+        this.visit(node.name);
+      }
+    } else {
+      this.visit(node.name);
+    }
     this.visitType(node.typeParameters);
     for (const attr of node.attributes) {
       this.visit(attr);

packages/scope-manager/tests/fixtures/jsx/children.tsx.shot

@@ -51,14 +51,6 @@ ScopeManager {
           resolved: null,
         },
         Reference$3,
-        Reference$4 {
-          identifier: JSXIdentifier$5,
-          isRead: true,
-          isTypeReference: false,
-          isValueReference: true,
-          isWrite: false,
-          resolved: null,
-        },
       ],
       set: Map {
         "const" => ImplicitGlobalConstTypeVariable,

packages/scope-manager/tests/fixtures/jsx/component-intrinsic-name.tsx

@@ -0,0 +1,2 @@
+function div() {} // should not be referenced
+<div />;

packages/scope-manager/tests/fixtures/jsx/component-intrinsic-name.tsx.shot

@@ -0,0 +1,58 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`jsx component-intrinsic-name 1`] = `
+ScopeManager {
+  variables: Array [
+    ImplicitGlobalConstTypeVariable,
+    Variable$2 {
+      defs: Array [
+        FunctionNameDefinition$1 {
+          name: Identifier<"div">,
+          node: FunctionDeclaration$1,
+        },
+      ],
+      name: "div",
+      references: Array [],
+      isValueVariable: true,
+      isTypeVariable: false,
+    },
+    Variable$3 {
+      defs: Array [],
+      name: "arguments",
+      references: Array [],
+      isValueVariable: true,
+      isTypeVariable: true,
+    },
+  ],
+  scopes: Array [
+    GlobalScope$1 {
+      block: Program$2,
+      isStrict: false,
+      references: Array [],
+      set: Map {
+        "const" => ImplicitGlobalConstTypeVariable,
+        "div" => Variable$2,
+      },
+      type: "global",
+      upper: null,
+      variables: Array [
+        ImplicitGlobalConstTypeVariable,
+        Variable$2,
+      ],
+    },
+    FunctionScope$2 {
+      block: FunctionDeclaration$1,
+      isStrict: false,
+      references: Array [],
+      set: Map {
+        "arguments" => Variable$3,
+      },
+      type: "function",
+      upper: GlobalScope$1,
+      variables: Array [
+        Variable$3,
+      ],
+    },
+  ],
+}
+`;

packages/scope-manager/tests/fixtures/jsx/component-namespaced.tsx.shot → packages/scope-manager/tests/fixtures/jsx/component-namespaced1.tsx.shot

@@ -1,6 +1,6 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`jsx component-namespaced 1`] = `
+exports[`jsx component-namespaced1 1`] = `
 ScopeManager {
   variables: Array [
     ImplicitGlobalConstTypeVariable,

packages/scope-manager/tests/fixtures/jsx/component-namespaced2.tsx

@@ -0,0 +1,6 @@
+const x = {
+  Foo() {},
+};
+const Foo = 1; // should be unreferenced
+
+<x.Foo />; // lower cased namespaces should still create a reference

packages/scope-manager/tests/fixtures/jsx/component-namespaced2.tsx.shot

@@ -0,0 +1,106 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`jsx component-namespaced2 1`] = `
+ScopeManager {
+  variables: Array [
+    ImplicitGlobalConstTypeVariable,
+    Variable$2 {
+      defs: Array [
+        VariableDefinition$1 {
+          name: Identifier<"x">,
+          node: VariableDeclarator$1,
+        },
+      ],
+      name: "x",
+      references: Array [
+        Reference$1 {
+          identifier: Identifier<"x">,
+          init: true,
+          isRead: false,
+          isTypeReference: false,
+          isValueReference: true,
+          isWrite: true,
+          resolved: Variable$2,
+          writeExpr: ObjectExpression$2,
+        },
+        Reference$3 {
+          identifier: JSXIdentifier$3,
+          isRead: true,
+          isTypeReference: false,
+          isValueReference: true,
+          isWrite: false,
+          resolved: Variable$2,
+        },
+      ],
+      isValueVariable: true,
+      isTypeVariable: false,
+    },
+    Variable$3 {
+      defs: Array [],
+      name: "arguments",
+      references: Array [],
+      isValueVariable: true,
+      isTypeVariable: true,
+    },
+    Variable$4 {
+      defs: Array [
+        VariableDefinition$2 {
+          name: Identifier<"Foo">,
+          node: VariableDeclarator$4,
+        },
+      ],
+      name: "Foo",
+      references: Array [
+        Reference$2 {
+          identifier: Identifier<"Foo">,
+          init: true,
+          isRead: false,
+          isTypeReference: false,
+          isValueReference: true,
+          isWrite: true,
+          resolved: Variable$4,
+          writeExpr: Literal$5,
+        },
+      ],
+      isValueVariable: true,
+      isTypeVariable: false,
+    },
+  ],
+  scopes: Array [
+    GlobalScope$1 {
+      block: Program$6,
+      isStrict: false,
+      references: Array [
+        Reference$1,
+        Reference$2,
+        Reference$3,
+      ],
+      set: Map {
+        "const" => ImplicitGlobalConstTypeVariable,
+        "x" => Variable$2,
+        "Foo" => Variable$4,
+      },
+      type: "global",
+      upper: null,
+      variables: Array [
+        ImplicitGlobalConstTypeVariable,
+        Variable$2,
+        Variable$4,
+      ],
+    },
+    FunctionScope$2 {
+      block: FunctionExpression$7,
+      isStrict: false,
+      references: Array [],
+      set: Map {
+        "arguments" => Variable$3,
+      },
+      type: "function",
+      upper: GlobalScope$1,
+      variables: Array [
+        Variable$3,
+      ],
+    },
+  ],
+}
+`;