fix: Do not show directory read errors

Author: hyperupcall

src/adapters/fileSystem.ts

@@ -1,5 +1,5 @@
 export type FileSystem = {
     fileExists: (filePath: string) => Promise<boolean>;
-    readFile: (filePath: string) => Promise<Error | string>;
-    writeFile: (filePath: string, contents: string) => Promise<Error | undefined>;
+    readFile: (filePath: string) => Promise<NodeJS.ErrnoException | string>;
+    writeFile: (filePath: string, contents: string) => Promise<NodeJS.ErrnoException | undefined>;
 };

src/converters/comments/convertFileComments.test.ts

@@ -6,7 +6,7 @@ import { createStubConverter } from "../lintConfigs/rules/ruleConverter.stubs";
 import { convertFileComments, ConvertFileCommentsDependencies } from "./convertFileComments";
 
 const createStubDependencies = (
-    readFileResult: string | Error,
+    readFileResult: string | NodeJS.ErrnoException,
 ): ConvertFileCommentsDependencies => ({
     converters: new Map([
         ["ts-a", createStubConverter(["es-a"])],
@@ -39,6 +39,24 @@ describe("convertFileComments", () => {
         expect(result).toBe(readFileError);
     });
 
+    it("ignores the failure when attempting to read a directory", async () => {
+        // Arrange
+        const readDirError = new Error() as NodeJS.ErrnoException;
+        readDirError.code = "EISDIR";
+        const dependencies = createStubDependencies(readDirError);
+
+        // Act
+        const result = await convertFileComments(
+            dependencies,
+            stubFileName,
+            new Map<string, string[]>(),
+            new Map<string, string[]>(),
+        );
+
+        // Assert
+        expect(result).toBe(undefined);
+    });
+
     it("doesn't overwrite a file when there are no matching comment directives", async () => {
         // Arrange
         const dependencies = createStubDependencies(`

src/converters/comments/convertFileComments.ts

@@ -16,6 +16,10 @@ export const convertFileComments = async (
 ) => {
     const fileContent = await dependencies.fileSystem.readFile(filePath);
     if (fileContent instanceof Error) {
+        if (fileContent.code === "EISDIR") {
+            return undefined;
+        }
+
         return fileContent;
     }