explicit-length-check: Check more cases (#941)

Author: fisker

docs/rules/explicit-length-check.md

@@ -1,6 +1,6 @@
 # Enforce explicitly comparing the `length` property of a value
 
-Enforce explicitly checking the length of an array in an `if` condition or ternary and enforce the comparison style.
+Enforce explicitly checking the length of an object and enforce the comparison style.
 
 This rule is fixable.
 
@@ -15,19 +15,19 @@ if (!foo.length) {}
 ```
 
 ```js
-if (foo.length == 0) {}
+while (foo.length == 0) {}
 ```
 
 ```js
-if (foo.length < 1) {}
+do {} while (foo.length < 1);
 ```
 
 ```js
-if (0 === foo.length) {}
+if (; 0 === foo.length;) {}
 ```
 
 ```js
-if (0 == foo.length) {}
+const unicorn = 0 == foo.length ? 1 : 2;
 ```
 
 ```js
@@ -60,19 +60,19 @@ if (foo.length !== 0) {}
 ```
 
 ```js
-if (foo.length != 0) {}
+while (foo.length != 0) {}
 ```
 
 ```js
-if (foo.length >= 1) {}
+do {} while (foo.length >= 1);
 ```
 
 ```js
-if (0 !== foo.length) {}
+for (; 0 !== foo.length; ) {}
 ```
 
 ```js
-if (0 != foo.length) {}
+const unicorn = 0 != foo.length ? 1 : 2;
 ```
 
 ```js

rules/explicit-length-check.js

@@ -113,6 +113,16 @@ function getZeroLengthNode(node) {
 	}
 }
 
+const selector = `:matches(${
+	[
+		'IfStatement',
+		'ConditionalExpression',
+		'WhileStatement',
+		'DoWhileStatement',
+		'ForStatement'
+	].join(', ')
+}) > *.test`;
+
 const create = context => {
 	const options = {
 		'non-zero': 'greater-than',
@@ -167,8 +177,8 @@ const create = context => {
 	}
 
 	return {
-		'IfStatement, ConditionalExpression': node => {
-			checkExpression(node.test);
+		[selector](node) {
+			checkExpression(node);
 		}
 	};
 };

test/explicit-length-check.js

@@ -58,6 +58,20 @@ test({
 
 		// `ConditionalExpression`
 		'const bar = foo.length === 0 ? 1 : 2',
+		// `WhileStatement`
+		outdent`
+			while (foo.length > 0) {
+				foo.pop();
+			}
+		`,
+		// `DoWhileStatement`
+		outdent`
+			do {
+				foo.pop();
+			} while (foo.length > 0);
+		`,
+		// `ForStatement`
+		'for (; foo.length > 0; foo.pop());',
 
 		'if (foo.length !== 1) {}',
 		'if (foo.length > 1) {}',
@@ -96,5 +110,8 @@ test.visualize([
 	'if (foo.bar && foo.bar.length) {}',
 	'if (foo.length || foo.bar()) {}',
 	'if (!!(!!foo.length)) {}',
-	'if (!(foo.length === 0)) {}'
+	'if (!(foo.length === 0)) {}',
+	'while (foo.length >= 1) {}',
+	'do {} while (foo.length);',
+	'for (let i = 0; (bar && !foo.length); i ++) {}'
 ]);

test/snapshots/explicit-length-check.js.md

@@ -779,3 +779,51 @@ Generated by [AVA](https://avajs.dev).
     > 1 | if (!(foo.length === 0)) {}␊
         |     ^^^^^^^^^^^^^^^^^^^ Use `.length > 0` when checking length is not zero.␊
     `
+
+## explicit-length-check - #8
+
+> Snapshot 1
+
+    `␊
+    Input:␊
+      1 | while (foo.length >= 1) {}␊
+    ␊
+    Output:␊
+      1 | while (foo.length > 0) {}␊
+    ␊
+    Error 1/1:␊
+    > 1 | while (foo.length >= 1) {}␊
+        |        ^^^^^^^^^^^^^^^ Use `.length > 0` when checking length is not zero.␊
+    `
+
+## explicit-length-check - #9
+
+> Snapshot 1
+
+    `␊
+    Input:␊
+      1 | do {} while (foo.length);␊
+    ␊
+    Output:␊
+      1 | do {} while (foo.length > 0);␊
+    ␊
+    Error 1/1:␊
+    > 1 | do {} while (foo.length);␊
+        |              ^^^^^^^^^^ Use `.length > 0` when checking length is not zero.␊
+    `
+
+## explicit-length-check - #10
+
+> Snapshot 1
+
+    `␊
+    Input:␊
+      1 | for (let i = 0; (bar && !foo.length); i ++) {}␊
+    ␊
+    Output:␊
+      1 | for (let i = 0; (bar && foo.length === 0); i ++) {}␊
+    ␊
+    Error 1/1:␊
+    > 1 | for (let i = 0; (bar && !foo.length); i ++) {}␊
+        |                         ^^^^^^^^^^^ Use `.length === 0` when checking length is zero.␊
+    `