fix: check path is string in pathToFsPath

There's a chance this function can be called with a path that is not a string.

To catch that, we check if path is of a different type and throw an error if it
is.

This also adds a couple tests for this function.

src/node/util.ts

@@ -10,6 +10,7 @@ import * as path from "path"
 import safeCompare from "safe-compare"
 import * as util from "util"
 import xdgBasedir from "xdg-basedir"
+import { getFirstString } from "../common/util"
 
 export interface Paths {
   data: string
@@ -457,10 +458,17 @@ enum CharCode {
  * Taken from vs/base/common/uri.ts. It's not imported to avoid also importing
  * everything that file imports.
  */
-export function pathToFsPath(path: string, keepDriveLetterCasing = false): string {
+export function pathToFsPath(path: string | string[], keepDriveLetterCasing = false): string {
   const isWindows = process.platform === "win32"
-  const uri = { authority: undefined, path, scheme: "file" }
+  const uri = { authority: undefined, path: getFirstString(path), scheme: "file" }
   let value: string
+
+  if (typeof uri.path !== "string") {
+    throw new Error(
+      `Could not compute fsPath from given uri. Expected path to be of type string, but was of type ${typeof uri.path}.`,
+    )
+  }
+
   if (uri.authority && uri.path.length > 1 && uri.scheme === "file") {
     // unc path: file://shares/c$/far/boo
     value = `//${uri.authority}${uri.path}`

test/unit/node/util.test.ts

@@ -453,3 +453,44 @@ describe("escapeHtml", () => {
     )
   })
 })
+
+describe("pathToFsPath", () => {
+  it("should convert a path to a file system path", () => {
+    expect(util.pathToFsPath("/foo/bar/baz")).toBe("/foo/bar/baz")
+  })
+  it("should lowercase drive letter casing by default", () => {
+    expect(util.pathToFsPath("/C:/far/boo")).toBe("c:/far/boo")
+  })
+  it("should keep drive letter casing when set to true", () => {
+    expect(util.pathToFsPath("/C:/far/bo", true)).toBe("C:/far/bo")
+  })
+  it("should throw an error if a non-string is passed in for path", () => {
+    expect(() =>
+      util
+        // @ts-expect-error We need to check other types
+        .pathToFsPath({}),
+    ).toThrow(
+      `Could not compute fsPath from given uri. Expected path to be of type string, but was of type undefined.`,
+    )
+  })
+  it("should not throw an error for a string array", () => {
+    // @ts-expect-error We need to check other types
+    expect(() => util.pathToFsPath(["/hello/foo", "/hello/bar"]).not.toThrow())
+  })
+  it("should use the first string in a string array", () => {
+    expect(util.pathToFsPath(["/hello/foo", "/hello/bar"])).toBe("/hello/foo")
+  })
+  it("should replace / with \\ on Windows", () => {
+    let ORIGINAL_PLATFORM = process.platform
+
+    Object.defineProperty(process, "platform", {
+      value: "win32",
+    })
+
+    expect(util.pathToFsPath("/C:/far/boo")).toBe("c:\\far\\boo")
+
+    Object.defineProperty(process, "platform", {
+      value: ORIGINAL_PLATFORM,
+    })
+  })
+})