refactor: enforce nullish checks

Author: Rel1cx

eslint.config.ts

@@ -71,19 +71,21 @@ const p11tGroups = {
 };
 
 const enableTypeCheckedRules = {
-  ...tseslint.configs.strictTypeCheckedOnly.map(x => x.rules).reduce((a, b) => ({ ...a, ...b }), {}),
+  ...tseslint.configs.strictTypeCheckedOnly
+    .map(x => x.rules)
+    .reduce((a, b) => ({ ...a, ...b }), {}),
   ...eslintPluginSafeTypeScript.configs.recommended.rules,
   "@susisu/safe-typescript/no-unsafe-object-property-check": "off",
   "@susisu/safe-typescript/no-unsafe-object-property-overwrite": "off",
   "@typescript-eslint/consistent-type-exports": "error",
-  "@typescript-eslint/strict-boolean-expressions": ["warn", {
+  "@typescript-eslint/strict-boolean-expressions": ["error", {
     allowAny: false,
     allowNullableBoolean: true,
     allowNullableEnum: false,
-    allowNullableNumber: false,
-    allowNullableObject: true,
+    allowNullableNumber: true,
+    allowNullableObject: false,
     allowNullableString: false,
-    allowNumber: false,
+    allowNumber: true,
     allowString: false,
   }],
 } as const;
@@ -150,11 +152,11 @@ export default tseslint.config(
     files: [...GLOB_JS, ...GLOB_TS],
     rules: {
       curly: "warn",
-      eqeqeq: ["error", "always"],
+      eqeqeq: ["error", "smart"],
       "no-console": "error",
       "no-else-return": "error",
       "no-fallthrough": ["error", { commentPattern: ".*intentional fallthrough.*" }],
-      "no-implicit-coercion": ["warn", { allow: ["!!"] }],
+      "no-implicit-coercion": "error",
       "no-mixed-operators": "warn",
       "no-process-exit": "error",
       "no-undef": "off",
@@ -256,6 +258,7 @@ export default tseslint.config(
       "eslint-plugin/require-meta-docs-url": "off",
       // Part: local rules
       "local/avoid-multiline-template-expression": "warn",
+      "local/prefer-eqeq-nullish-comparison": "warn",
     },
     settings: {
       "import-x/parsers": {

packages/core/src/component/component-collector.ts

@@ -87,7 +87,7 @@ export function useComponentCollector(
       .reverse()
       .some(r => {
         return context.sourceCode.getScope(r).block === entry.node
-          && r.argument !== null
+          && r.argument != null
           && !JSX.isJSXValue(r.argument, jsxCtx, hint);
       });
     if (shouldDrop) {
@@ -153,7 +153,7 @@ export function useComponentCollector(
       const component = Array
         .from(components.values())
         .findLast(({ name }) => O.exists(name, n => n === componentName));
-      if (!component) {
+      if (component == null) {
         return;
       }
       components.set(component._, {

packages/core/src/component/component-name.ts

@@ -9,5 +9,5 @@ export function getComponentNameFromIdentifier(node: TSESTree.Identifier | TSEST
 }
 
 export function isComponentName(name: string) {
-  return !!name && RE_COMPONENT_NAME.test(name);
+  return RE_COMPONENT_NAME.test(name);
 }

packages/core/src/component/is.ts

@@ -8,7 +8,7 @@ import { AST_NODE_TYPES as T } from "@typescript-eslint/types";
  * @returns `true` if the node is a class component, `false` otherwise
  */
 export function isClassComponent(node: TSESTree.Node): node is AST.TSESTreeClass {
-  if ("superClass" in node && node.superClass) {
+  if ("superClass" in node && node.superClass != null) {
     const re = /^(?:Pure)?Component$/u;
     switch (true) {
       case node.superClass.type === T.Identifier:
@@ -27,7 +27,7 @@ export function isClassComponent(node: TSESTree.Node): node is AST.TSESTreeClass
  * @returns `true` if the node is a pure component, `false` otherwise
  */
 export function isPureComponent(node: TSESTree.Node) {
-  if ("superClass" in node && node.superClass) {
+  if ("superClass" in node && node.superClass != null) {
     const re = /^PureComponent$/u;
     switch (true) {
       case node.superClass.type === T.Identifier:

packages/core/src/component/misc.ts

@@ -14,5 +14,5 @@ export function hasNoneOrValidComponentName(node: AST.TSESTreeFunction, context:
   const name = Array.isArray(id)
     ? id.at(-1)?.name
     : id.name;
-  return !!name && isComponentName(name);
+  return name != null && isComponentName(name);
 }

packages/core/src/effect/is.ts

@@ -1,5 +1,5 @@
 import * as AST from "@eslint-react/ast";
-import { O } from "@eslint-react/eff";
+import { F, O } from "@eslint-react/eff";
 import type { TSESTree } from "@typescript-eslint/types";
 import { AST_NODE_TYPES as T } from "@typescript-eslint/types";
 
@@ -14,14 +14,14 @@ export function isSetupFunction(node: TSESTree.Node) {
 }
 
 export function isCleanupFunction(node: TSESTree.Node) {
-  const nearestRet = O.getOrNull(AST.findParentNodeGuard(node, AST.is(T.ReturnStatement)));
-  if (!nearestRet) {
-    return false;
-  }
-  const nearestFunction = O.getOrNull(AST.findParentNodeGuard(node, AST.isFunction));
-  const nearestFunctionOfRet = O.getOrNull(AST.findParentNodeGuard(nearestRet, AST.isFunction));
-  if (!nearestFunction || !nearestFunctionOfRet) {
-    return false;
-  }
-  return nearestFunction === nearestFunctionOfRet && isSetupFunction(nearestFunction);
+  return F.pipe(
+    O.Do,
+    O.bind("nearReturn", () => AST.findParentNodeGuard(node, AST.is(T.ReturnStatement))),
+    O.bind("nearFunction", () => AST.findParentNodeGuard(node, AST.isFunction)),
+    O.bind("nearFunctionOfReturn", ({ nearReturn }) => AST.findParentNodeGuard(nearReturn, AST.isFunction)),
+    O.exists(({ nearFunction, nearFunctionOfReturn }) =>
+      nearFunction === nearFunctionOfReturn
+      && isSetupFunction(nearFunction)
+    ),
+  );
 }

packages/core/src/hook/hook-collector.ts

@@ -49,7 +49,7 @@ export function useHookCollector() {
         return;
       }
       const [fNode, hookId] = fStack.at(-1) ?? [];
-      if (!fNode || !hookId) {
+      if (fNode == null || hookId == null) {
         return;
       }
       F.pipe(

packages/core/src/utils/is-react-api.ts

@@ -3,17 +3,17 @@ import { isCallFromReact, isCallFromReactMember, isFromReact, isFromReactMember
 export function isReactAPIWithName(name: string): ReturnType<typeof isFromReact>;
 export function isReactAPIWithName(name: string, member: string): ReturnType<typeof isFromReactMember>;
 export function isReactAPIWithName(name: string, member?: string) {
-  return member
-    ? isFromReactMember(name, member)
-    : isFromReact(name);
+  return member == null
+    ? isFromReact(name)
+    : isFromReactMember(name, member);
 }
 
 export function isReactAPICallWithName(name: string): ReturnType<typeof isCallFromReact>;
 export function isReactAPICallWithName(name: string, member: string): ReturnType<typeof isCallFromReactMember>;
 export function isReactAPICallWithName(name: string, member?: string) {
-  return member
-    ? isCallFromReactMember(name, member)
-    : isCallFromReact(name);
+  return member == null
+    ? isCallFromReact(name)
+    : isCallFromReactMember(name, member);
 }
 
 export const isChildrenCount = isReactAPIWithName("Children", "count");

packages/plugins/eslint-plugin-react-debug/src/rules/function-component.ts

@@ -40,9 +40,9 @@ export default createRule<[], MessageID>({
             node,
             data: {
               name: O.getOrElse(name, F.constant("anonymous")),
-              forwardRef: Boolean(flag & ERFunctionComponentFlag.ForwardRef),
+              forwardRef: (flag & ERFunctionComponentFlag.ForwardRef) > 0n,
               hookCalls: hookCalls.length,
-              memo: Boolean(flag & ERFunctionComponentFlag.Memo),
+              memo: (flag & ERFunctionComponentFlag.Memo) > 0n,
             },
           });
         }

packages/plugins/eslint-plugin-react-dom/src/rules/no-script-url.ts

@@ -35,7 +35,7 @@ export default createRule<[], MessageID>({
   create(context) {
     return {
       JSXAttribute(node) {
-        if (node.name.type !== T.JSXIdentifier || !node.value) {
+        if (node.name.type !== T.JSXIdentifier || node.value == null) {
           return;
         }
         const isJavaScript = F.pipe(