feat: support for boolean project option

Author: ota-meshi

src/index.ts

@@ -2,6 +2,7 @@ import type { ParserOptions } from "@typescript-eslint/parser";
 import type { ProgramOptions } from "./ts";
 import { TSServiceManager } from "./ts";
 import * as tsEslintParser from "@typescript-eslint/parser";
+import { getProjectConfigFiles } from "./utils/get-project-config-files";
 
 const DEFAULT_EXTRA_FILE_EXTENSIONS = [".vue", ".svelte", ".astro"];
 const tsServiceManager = new TSServiceManager();
@@ -47,9 +48,7 @@ function* iterateOptions(options: ParserOptions): Iterable<ProgramOptions> {
       "Specify `parserOptions.project`. Otherwise there is no point in using this parser."
     );
   }
-  for (const project of Array.isArray(options.project)
-    ? options.project
-    : [options.project]) {
+  for (const project of getProjectConfigFiles(options)) {
     yield {
       project,
       filePath: options.filePath,

src/utils/get-project-config-files.ts

@@ -0,0 +1,32 @@
+import type { ParserOptions } from "@typescript-eslint/parser";
+import fs from "fs";
+import path from "path";
+
+export function getProjectConfigFiles(options: ParserOptions): string[] {
+  const tsconfigRootDir =
+    typeof options.tsconfigRootDir === "string"
+      ? options.tsconfigRootDir
+      : process.cwd();
+  if (options.project !== true) {
+    return Array.isArray(options.project)
+      ? options.project
+      : [options.project!];
+  }
+
+  let directory = path.dirname(options.filePath!);
+  const checkedDirectories = [directory];
+
+  do {
+    const tsconfigPath = path.join(directory, "tsconfig.json");
+    if (fs.existsSync(tsconfigPath)) {
+      return [tsconfigPath];
+    }
+
+    directory = path.dirname(directory);
+    checkedDirectories.push(directory);
+  } while (directory.length > 1 && directory.length >= tsconfigRootDir.length);
+
+  throw new Error(
+    `project was set to \`true\` but couldn't find any tsconfig.json relative to '${options.filePath}' within '${tsconfigRootDir}'.`
+  );
+}