more wip

src/helpers.ts

@@ -1,4 +1,3 @@
-/* eslint no-nested-ternary: off */
 import type { Rule } from "eslint";
 import type * as ESTree from "estree";
 import browserslist from "browserslist";
@@ -15,40 +14,34 @@ import { TargetNameMappings } from "./constants";
 - Each API is given to versioning.ts with compatibility info
 */
 
-enum GuardType {
-  // Guard is true if the browser supports the API
-  POSITIVE,
-  // Guard is false if the browser supports the API
-  NEGATIVE,
-}
-
 export interface GuardedScope {
-  scope: ESTree.Node & Rule.NodeParentExtension;
+  scope: Rule.Node;
   index: number;
 }
 
 /**
- * Checks if the given node is used in a guard, and whether it's used to guard for or against the
- * block statement. Should be called with either a bare Identifier, or a MemberExpression.
+ * Checks if the given node is used in an if statement, and if it is, returns the
+ * scope that the guard applies to and after which index it applies.
+ * Should be called with either a bare Identifier or a MemberExpression.
  */
 export function determineGuardedScope(
   node: (ESTree.Identifier | ESTree.MemberExpression) & Rule.NodeParentExtension
 ): GuardedScope | null {
   const result = getIfStatementAndGuardType(node);
   if (!result) return null;
 
-  const [ifStatement, guardType] = result;
+  const [ifStatement, positiveGuard] = result;
 
-  if (guardType === GuardType.POSITIVE) {
-    return { scope: ifStatement.consequent as GuardedScope["scope"], index: 0 };
+  if (positiveGuard) {
+    // It's okay to use the identifier inside of the if statement
+    return { scope: ifStatement.consequent as Rule.Node, index: 0 };
   }
 
-  // guardType is NEGATIVE
-
   if (
     ifStatementHasEarlyReturn(ifStatement) &&
     isBlockOrProgram(ifStatement.parent)
   ) {
+    // It's okay to use the identifier after the if statement
     const scope = ifStatement.parent;
     const index = scope.body.indexOf(ifStatement) + 1;
     return { scope, index };
@@ -65,9 +58,9 @@ export function isBlockOrProgram(
 
 function getIfStatementAndGuardType(
   node: (ESTree.Identifier | ESTree.MemberExpression) & Rule.NodeParentExtension
-): [ESTree.IfStatement & Rule.NodeParentExtension, GuardType] | null {
-  let guardType = GuardType.POSITIVE;
-  let expression: ESTree.Node & Rule.NodeParentExtension = node;
+): [ESTree.IfStatement & Rule.NodeParentExtension, boolean] | null {
+  let positiveGuard = true;
+  let expression: Rule.Node = node;
 
   if (
     node.parent?.type === "UnaryExpression" &&
@@ -92,11 +85,11 @@ function getIfStatementAndGuardType(
     ) {
       // typeof foo === "function"
       // typeof foo !== "undefined"
-      guardType = GuardType.POSITIVE;
+      positiveGuard = true;
     } else {
       // typeof foo !== "function"
       // typepf foo === "undefined"
-      guardType = GuardType.NEGATIVE;
+      positiveGuard = false;
     }
   }
 
@@ -109,20 +102,17 @@ function getIfStatementAndGuardType(
     expression.parent.operator === "!"
   ) {
     expression = expression.parent;
-    if (guardType === GuardType.POSITIVE) {
-      guardType = GuardType.NEGATIVE;
-    } else {
-      guardType = GuardType.POSITIVE;
-    }
+    positiveGuard = !positiveGuard;
   }
 
+  // TODO: allow && checks, but || checks aren't really safe
   // skip over && and || expressions
   while (expression.parent?.type === "LogicalExpression") {
     expression = expression.parent;
   }
 
   if (expression.parent?.type === "IfStatement") {
-    return [expression.parent, guardType];
+    return [expression.parent, positiveGuard];
   }
 
   return null;

src/rules/compat.ts

@@ -246,7 +246,7 @@ const ruleModule: Rule.RuleModule = {
 
         let object = "window";
 
-        let expression: ESTree.Node & Rule.NodeParentExtension = node;
+        let expression: Rule.Node = node;
         if (expression.parent.type === "MemberExpression") {
           expression = expression.parent;
           if (expression.object.type === "MemberExpression") {