feat: add ignoreConditionalChecks setting

Allow reporting inside feature-detection conditionals.

Document the new setting.

Author: tujoworker

README.md

@@ -94,6 +94,19 @@ This plugin also supports linting the compatibility of ES APIs in addition to We
 }
 ```
 
+## Conditional Checks
+
+By default, feature detection like `if (fetch) { ... }` does not trigger a
+report. To lint these conditionals anyway, set the following:
+
+```jsonc
+{
+  "settings": {
+    "ignoreConditionalChecks": true,
+  },
+}
+```
+
 ## Configuring for Different Environments
 
 Browserslist allows specifying [different browser queries for multiple environments](https://github.com/browserslist/browserslist#configuring-for-different-environments). By default, this plugin targets the `production` browserslist environment. To change this default, set the `settings.browserslistOpts.env` property in your eslint config:

docs/rules/compat.md

@@ -15,3 +15,9 @@ fetch("https://exmaple.com");
 // Using default browser targets
 fetch("https://exmaple.com");
 ```
+
+## Conditional Checks
+
+By default, feature detection like `if (fetch) { ... }` does not trigger a
+report. Set `settings.ignoreConditionalChecks` to `true` to lint these
+conditionals.

src/helpers.ts

@@ -50,7 +50,10 @@ function checkNotInsideIfStatementAndReport(
   sourceCode: SourceCode,
   node: ESLintNode
 ) {
-  if (!isInsideIfStatement(node, sourceCode, context)) {
+  if (
+    context.settings?.ignoreConditionalChecks === true ||
+    !isInsideIfStatement(node, sourceCode, context)
+  ) {
     handleFailingRule(failingRule, node);
   }
 }

src/types.ts

@@ -79,6 +79,7 @@ export interface Context extends Rule.RuleContext {
     browsers?: Array<string>;
     polyfills?: Array<string>;
     lintAllEsApis?: boolean;
+    ignoreConditionalChecks?: boolean;
     browserslistOpts?: BrowsersListOpts;
   };
 }

test/e2e.spec.ts

@@ -276,6 +276,22 @@ ruleTester.run("compat", rule, {
     },
   ],
   invalid: [
+    {
+      code: `
+        if (fetch) {
+          fetch()
+        }
+      `,
+      settings: {
+        browsers: ["ExplorerMobile 10"],
+        ignoreConditionalChecks: true,
+      },
+      errors: [
+        {
+          message: "fetch is not supported in IE Mobile 10",
+        },
+      ],
+    },
     {
       code: "window?.fetch?.('example.com')",
       settings: { browsers: ["ie 9"] },