fix(pathlib): make Path constructor emit positional args

Fable emits primary-ctor parameters as Python kwargs, but
pathlib.Path.__init__ does not accept `path=` as a keyword, breaking
27 tests with `TypeError: PurePath.__init__() got an unexpected
keyword argument 'path'`. Switch to a no-arg primary ctor and declare
the string and varargs ctors via [<Emit>] so emission stays
positional. Also relax suffixes/parents/parts to `seq<_>` to match the
underlying tuple/list/_PathParents return types, and wrap the byte
fixture in builtins.bytes so write_bytes receives a real bytes object
instead of a fable.UInt8Array.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dbrattli

src/stdlib/Pathlib.fs

@@ -8,13 +8,20 @@ open Fable.Core
 
 /// Represents a filesystem path on the current OS (POSIX or Windows).
 /// Paths are immutable; operations return new Path instances.
+///
+/// `Path()` represents the current directory (`.`). For multi-segment construction
+/// use the `/` operator (`Path "a" / "b" / "c"`) or `joinpath`.
 /// See https://docs.python.org/3/library/pathlib.html#pathlib.Path
 [<Import("Path", "pathlib")>]
-type Path(path: string) =
+type Path() =
+    /// Construct a Path from a single string segment.
+    [<Emit("Path($0)")>]
+    new(path: string) = Path()
+
     /// Construct a Path by joining multiple path segments.
-    /// Equivalent to Path(parts[0]) / parts[1] / …
+    /// Equivalent to ``Path(parts[0]) / parts[1] / …``.
     [<Emit("Path($0...)")>]
-    new([<ParamArray>] paths: string[]) = Path("")
+    new([<ParamArray>] paths: string[]) = Path()
 
     // -------------------------------------------------------------------------
     // Properties
@@ -34,19 +41,19 @@ type Path(path: string) =
 
     /// All file extensions of the final component (e.g. [".tar"; ".gz"]).
     /// See https://docs.python.org/3/library/pathlib.html#pathlib.PurePath.suffixes
-    member _.suffixes: ResizeArray<string> = nativeOnly
+    member _.suffixes: string seq = nativeOnly
 
     /// The logical parent of the path (directory containing this path).
     /// See https://docs.python.org/3/library/pathlib.html#pathlib.PurePath.parent
     member _.parent: Path = nativeOnly
 
     /// Immutable sequence of the logical ancestors of the path.
     /// See https://docs.python.org/3/library/pathlib.html#pathlib.PurePath.parents
-    member _.parents: ResizeArray<Path> = nativeOnly
+    member _.parents: Path seq = nativeOnly
 
     /// The path's components as a tuple of strings.
     /// See https://docs.python.org/3/library/pathlib.html#pathlib.PurePath.parts
-    member _.parts: ResizeArray<string> = nativeOnly
+    member _.parts: string seq = nativeOnly
 
     /// The root component of the path (e.g. "/" on POSIX), or "".
     /// See https://docs.python.org/3/library/pathlib.html#pathlib.PurePath.root

test/TestPathlib.fs

@@ -2,6 +2,7 @@ module Fable.Python.Tests.Pathlib
 
 open Fable.Python.Testing
 open Fable.Python.Pathlib
+open Fable.Python.Builtins
 
 // ============================================================================
 // Construction
@@ -12,6 +13,11 @@ let ``test Path construction from string`` () =
     let p = Path "/tmp"
     p.str () |> equal "/tmp"
 
+[<Fact>]
+let ``test Path construction from multiple segments`` () =
+    let p = Path("/foo", "bar", "baz.txt")
+    p.str () |> equal "/foo/bar/baz.txt"
+
 [<Fact>]
 let ``test Path cwd returns absolute path`` () =
     let p = Path.cwd ()
@@ -201,7 +207,7 @@ let ``test Path write_text and read_text`` () =
 [<Fact>]
 let ``test Path write_bytes and read_bytes`` () =
     let tmp = Path.cwd () / "__pathlib_test_bytes__.bin"
-    let data: byte[] = [| 0uy; 1uy; 2uy; 255uy |]
+    let data = builtins.bytes [| 0uy; 1uy; 2uy; 255uy |]
     tmp.write_bytes data |> ignore
     let result = tmp.read_bytes ()
     tmp.unlink (missing_ok = true)