From 5b5d06101005eaecee153fdc5c8b9153055011a6 Mon Sep 17 00:00:00 2001
From: tanmoyopenroot <tanmoy.openroot@gmail.com>
Date: Fri, 9 Aug 2019 11:11:28 +0530
Subject: [PATCH] add new rule: react-no-unnecessary-fragment

---
 src/rules/reactNoUnnecessaryFragmentRule.ts   |  98 ++++++++++
 .../test.tsx.lint                             | 182 ++++++++++++++++++
 .../react-no-unnecessary-fragment/tslint.json |   5 +
 3 files changed, 285 insertions(+)
 create mode 100644 src/rules/reactNoUnnecessaryFragmentRule.ts
 create mode 100644 test/rules/react-no-unnecessary-fragment/test.tsx.lint
 create mode 100644 test/rules/react-no-unnecessary-fragment/tslint.json

diff --git a/src/rules/reactNoUnnecessaryFragmentRule.ts b/src/rules/reactNoUnnecessaryFragmentRule.ts
new file mode 100644
index 0000000..516c761
--- /dev/null
+++ b/src/rules/reactNoUnnecessaryFragmentRule.ts
@@ -0,0 +1,98 @@
+/**
+ * @license
+ * Copyright 2019 Palantir Technologies, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as Lint from "tslint";
+import {
+    isJsxElement,
+    isJsxFragment,
+    isJsxOpeningFragment,
+    isJsxSelfClosingElement,
+    isJsxText,
+} from "tsutils/typeguard/3.0";
+import * as ts from "typescript";
+
+const FRAGMENT_TAGNAME = "Fragment";
+const REACT_FRAGEMNT_TAGNAME = "React.Fragment";
+
+export class Rule extends Lint.Rules.AbstractRule {
+    public static metadata: Lint.IRuleMetadata = {
+        description: Lint.Utils.dedent`
+            Warn if unnecessary fragment is used'
+        `,
+        optionExamples: ["true"],
+        options: null,
+        optionsDescription: "",
+        ruleName: "react-no-unnecessary-fragment",
+        type: "style",
+        typescriptOnly: false,
+    };
+
+    public static FAILURE_STRING = "Unnecessary Fragment are forbidden";
+
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithFunction(sourceFile, walk);
+    }
+}
+
+function walk(ctx: Lint.WalkContext<void>): void {
+    return ts.forEachChild(ctx.sourceFile, function cb(node: ts.Node): void {
+        if (
+            (isJsxFragment(node) && isJsxOpeningFragment(node.openingFragment)) ||
+            (isJsxElement(node) && isJSXFragmentElement(node.openingElement))
+        ) {
+            let numValidChildren = 0;
+
+            for (const child of node.children) {
+                if (isJsxText(child)) {
+                    if (!isInvalidJSXText(child)) {
+                        numValidChildren += 1;
+                    }
+                } else {
+                    numValidChildren += 1;
+                }
+
+                if (numValidChildren > 1) {
+                    break;
+                }
+            }
+
+            if (numValidChildren <= 1) {
+                ctx.addFailureAtNode(node, Rule.FAILURE_STRING);
+            }
+
+        } else if (isJsxSelfClosingElement(node) && isJSXFragmentElement(node)) {
+            ctx.addFailureAtNode(node, Rule.FAILURE_STRING);
+        }
+
+        return ts.forEachChild(node, cb);
+    });
+}
+
+function isJSXFragmentElement(node: ts.JsxSelfClosingElement | ts.JsxOpeningElement): boolean {
+    if (
+        node.tagName.getText() === FRAGMENT_TAGNAME ||
+        node.tagName.getText() === REACT_FRAGEMNT_TAGNAME
+    ) {
+        return true;
+    }
+
+    return false;
+}
+
+function isInvalidJSXText(node: ts.JsxText): boolean {
+    return node.getText().trim() === "" ? true : false;
+}
diff --git a/test/rules/react-no-unnecessary-fragment/test.tsx.lint b/test/rules/react-no-unnecessary-fragment/test.tsx.lint
new file mode 100644
index 0000000..e2f53f8
--- /dev/null
+++ b/test/rules/react-no-unnecessary-fragment/test.tsx.lint
@@ -0,0 +1,182 @@
+<React.Fragment>
+~~~~~~~~~~~~~~~~
+    <div>
+~~~~~~~~~
+        <Component1 />
+~~~~~~~~~~~~~~~~~~~~~~
+        <Component2 />
+~~~~~~~~~~~~~~~~~~~~~~
+        <Component3 />
+~~~~~~~~~~~~~~~~~~~~~~
+    </div>
+~~~~~~~~~~
+</React.Fragment>
+~~~~~~~~~~~~~~~~~ [FAILURE_STRING]
+
+<React.Fragment>test
+    <div>
+        <Component1 />
+        <Component2 />
+        <Component3 />
+    </div></React.Fragment>
+
+<React.Fragment>
+~~~~~~~~~~~~~~~~
+    <React.Fragment>
+~~~~~~~~~~~~~~~~~~~~
+        <Component1 />
+~~~~~~~~~~~~~~~~~~~~~~
+        <Component2 />
+~~~~~~~~~~~~~~~~~~~~~~
+        <Component3 />
+~~~~~~~~~~~~~~~~~~~~~~
+    </React.Fragment>
+~~~~~~~~~~~~~~~~~~~~~
+</React.Fragment>
+~~~~~~~~~~~~~~~~~ [FAILURE_STRING]
+
+<React.Fragment>
+~~~~~~~~~~~~~~~~
+    <React.Fragment>
+~~~~~~~~~~~~~~~~~~~~
+    ~~~~~~~~~~~~~~~~
+        <>
+~~~~~~~~~~
+~~~~~~~~~~
+            <Component1 />
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+            <Component2 />
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+            <Component3 />
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+        </>
+~~~~~~~~~~~
+~~~~~~~~~~~
+    </React.Fragment>
+~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~ [FAILURE_STRING]
+</React.Fragment>
+~~~~~~~~~~~~~~~~~ [FAILURE_STRING]
+
+<>
+~~
+    <>
+~~~~~~
+    ~~
+        <>
+~~~~~~~~~~
+~~~~~~~~~~
+            <Component1 />
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+            <Component2 />
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+            <Component3 />
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+        </>
+~~~~~~~~~~~
+~~~~~~~~~~~
+    </>
+~~~~~~~
+~~~~~~~ [FAILURE_STRING]
+</>
+~~~ [FAILURE_STRING]
+
+<>
+~~
+    <Fragment>
+~~~~~~~~~~~~~~
+    ~~~~~~~~~~
+        <>
+~~~~~~~~~~
+~~~~~~~~~~
+            <Component1 />
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+            <Component2 />
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+            <Component3 />
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+        </>
+~~~~~~~~~~~
+~~~~~~~~~~~
+    </Fragment>
+~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~ [FAILURE_STRING]
+</>
+~~~ [FAILURE_STRING]
+
+<Fragment>
+~~~~~~~~~~
+    <Fragment>
+~~~~~~~~~~~~~~
+        <Component1 />
+~~~~~~~~~~~~~~~~~~~~~~
+        <Component2 />
+~~~~~~~~~~~~~~~~~~~~~~
+        <Component3 />
+~~~~~~~~~~~~~~~~~~~~~~
+    </Fragment>
+~~~~~~~~~~~~~~~
+</Fragment>
+~~~~~~~~~~~ [FAILURE_STRING]
+
+<Fragment>
+  	test
+    <div>
+        <Component1 />
+        <Component2 />
+        <Component3 />
+    </div></Fragment>
+      
+<Fragment>
+      <Component1 />
+      <Component2 />
+</Fragment>
+
+<Fragment>
+~~~~~~~~~~
+</Fragment>
+~~~~~~~~~~~ [FAILURE_STRING]
+
+<React.Fragment>
+~~~~~~~~~~~~~~~~
+</React.Fragment>
+~~~~~~~~~~~~~~~~~ [FAILURE_STRING]
+
+<Fragment><Component1 /><Component2 /></Fragment>
+
+<Fragment></Fragment>
+~~~~~~~~~~~~~~~~~~~~~ [FAILURE_STRING]
+
+<React.Fragment></React.Fragment>
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [FAILURE_STRING]
+
+<Fragment />
+~~~~~~~~~~~~ [FAILURE_STRING]
+
+<React.Fragment />
+~~~~~~~~~~~~~~~~~~ [FAILURE_STRING]
+          
+<>
+~~
+    <div>
+~~~~~~~~~
+        <Component1 />
+~~~~~~~~~~~~~~~~~~~~~~
+        <Component2 />
+~~~~~~~~~~~~~~~~~~~~~~
+        <Component3 />
+~~~~~~~~~~~~~~~~~~~~~~
+    </div>
+~~~~~~~~~~
+</>
+~~~ [FAILURE_STRING]
+[FAILURE_STRING]: Unnecessary Fragment are forbidden
diff --git a/test/rules/react-no-unnecessary-fragment/tslint.json b/test/rules/react-no-unnecessary-fragment/tslint.json
new file mode 100644
index 0000000..eb73b26
--- /dev/null
+++ b/test/rules/react-no-unnecessary-fragment/tslint.json
@@ -0,0 +1,5 @@
+{
+    "rules": {
+        "react-no-unnecessary-fragment": true
+    }
+}