Fix crash when used with TypeScript (#379)

Co-authored-by: Michael Schmidt <mitchi5000.ms@googlemail.com>

Author: ota-meshi

lib/rules/prefer-result-array-groups.ts

@@ -146,7 +146,8 @@ export default createRule("prefer-result-array-groups", {
                 return "unknown"
             }
             const tsNode = tsNodeMap.get(node)
-            const tsType = (tsNode && checker.getTypeAtLocation(tsNode)) || null
+            const tsType =
+                (tsNode && checker?.getTypeAtLocation(tsNode)) || null
             if (!tsType) {
                 // The node type cannot be determined.
                 return "unknown"

lib/utils/ts-utils/index.ts

@@ -8,22 +8,24 @@ type TypeScript = typeof import("typescript")
  */
 export function getTypeScriptTools(context: Rule.RuleContext): {
     tsNodeMap: ReadonlyMap<unknown, TS.Node>
-    checker: TS.TypeChecker
+    checker: TS.TypeChecker | null
     usedTS: boolean
     hasFullTypeInformation: boolean
 } {
     const ts = getTypeScript()
-    const tsNodeMap: ReadonlyMap<unknown, TS.Node> =
+    const tsNodeMap: ReadonlyMap<unknown, TS.Node> | undefined =
         context.parserServices.esTreeNodeToTSNodeMap
-    const checker: TS.TypeChecker =
-        context.parserServices.program &&
-        context.parserServices.program.getTypeChecker()
-    const usedTS = Boolean(ts && tsNodeMap && checker)
+    const usedTS = Boolean(ts && tsNodeMap)
     const hasFullTypeInformation =
         usedTS && context.parserServices.hasFullTypeInformation !== false
+    const checker: TS.TypeChecker | null =
+        (hasFullTypeInformation &&
+            context.parserServices.program &&
+            context.parserServices.program.getTypeChecker()) ||
+        null
 
     return {
-        tsNodeMap,
+        tsNodeMap: tsNodeMap || new Map(),
         checker,
         usedTS,
         hasFullTypeInformation,

lib/utils/type-tracker/index.ts

@@ -513,7 +513,7 @@ export function createTypeTracker(context: Rule.RuleContext): TypeTracker {
      */
     function getTypeByTs(node: ES.Expression): TypeInfo | null {
         const tsNode = tsNodeMap.get(node)
-        const tsType = (tsNode && checker.getTypeAtLocation(tsNode)) || null
+        const tsType = (tsNode && checker?.getTypeAtLocation(tsNode)) || null
         return tsType && getTypeFromTsType(tsType)
     }
 
@@ -575,7 +575,7 @@ export function createTypeTracker(context: Rule.RuleContext): TypeTracker {
         if (isObject(tsType)) {
             return UNKNOWN_OBJECT
         }
-        return checker.typeToString(tsType) as TypeInfo
+        return checker ? (checker.typeToString(tsType) as TypeInfo) : null
     }
 
     /**
@@ -590,7 +590,7 @@ export function createTypeTracker(context: Rule.RuleContext): TypeTracker {
             ts.isTypeParameterDeclaration(declaration) &&
             declaration.constraint != null
         ) {
-            return checker.getTypeFromTypeNode(declaration.constraint)
+            return checker?.getTypeFromTypeNode(declaration.constraint)
         }
         return undefined
     }

tests/lib/rules/no-legacy-features.ts

@@ -32,7 +32,21 @@ const STATIC_PROPERTIES: string[] = [
 const PROTOTYPE_METHODS: string[] = ["compile"]
 
 tester.run("no-legacy-features", rule as any, {
-    valid: [`RegExp`, `new RegExp()`, `RegExp.unknown`],
+    valid: [
+        `RegExp`,
+        `new RegExp()`,
+        `RegExp.unknown`,
+        {
+            // https://github.com/ota-meshi/eslint-plugin-regexp/issues/378
+            filename: "loglevel.d.ts",
+            code: `
+            import log from 'loglevel';
+            export as namespace log;
+            export = log;
+            `,
+            parser: require.resolve("@typescript-eslint/parser"),
+        },
+    ],
     invalid: [
         ...STATIC_PROPERTIES.map((sp) => {
             return {