Format 1-element tuples as "(x,)" (#521)

* Format 1-element tuples as "(x,)"

Currently, single-element tuple "repr" / "str" gives "(x)", but it should really give "(x,)" according to Python.

* Fix tests

stdlib/internal/internal.codon

@@ -427,6 +427,16 @@ class __internal__:
         return str(buf, total)
 
     def tuple_str(strs: Ptr[str], names: Ptr[str], n: int) -> str:
+        # special case of 1-element plain tuple: format as "(x,)"
+        if n == 1 and names[0].len == 0:
+            total = strs[0].len + 3
+            buf = Ptr[byte](total)
+            buf[0] = byte(40)  # '('
+            str.memcpy(buf + 1, strs[0].ptr, strs[0].len)
+            buf[total - 2] = byte(44)  # ','
+            buf[total - 1] = byte(41)  # ')'
+            return str(buf, total)
+
         total = 2  # one for each of '(' and ')'
         i = 0
         while i < n:

test/core/containers.codon

@@ -93,6 +93,13 @@ def test_tuple():
     assert a[0:] == 3
     assert a[0:1] == 42
     assert a[:] == -1
+
+    assert str((11, 2, 333)) == '(11, 2, 333)'
+    assert str(()) == '()'
+    assert str((42,)) == '(42,)'
+    assert repr((11, 2, 333)) == '(11, 2, 333)'
+    assert repr(()) == '()'
+    assert repr((42,)) == '(42,)'
 test_tuple()
 
 @test

test/parser/simplify_expr.codon

@@ -255,7 +255,7 @@ t: tuple[int, int] = (1, 2)
 print t #: (1, 2)
 
 tt: Tuple[int] = (1, )
-print tt #: (1)
+print tt #: (1,)
 
 def foo(i: int) -> int:
     return i + 1

test/parser/typecheck_expr.codon

@@ -206,7 +206,7 @@ print z[:1], z[1:], z[1:3], z[:4:2], z[::-1]  #: [1] [2, 3, 4, 5] [2, 3] [1, 3]
 a = (1, '2s', 3.3)
 print a[1] #: 2s
 print a[0:2], a[:2], a[1:] #: (1, '2s') (1, '2s') ('2s', 3.3)
-print a[0:3:2], a[-1:] #: (1, 3.3) (3.3)
+print a[0:3:2], a[-1:] #: (1, 3.3) (3.3,)
 
 #%% static_index_side,barebones
 def foo(a):
@@ -470,14 +470,14 @@ p('s', zh=65) #: s () (zh: 65)
 q = p(zh=43, ...)
 q(1) #: 1 () (zh: 43)
 r = q(5, 38, ...)
-r() #: 5 (38) (zh: 43)
+r() #: 5 (38,) (zh: 43)
 r(1, a=1) #: 5 (38, 1) (zh: 43, a: 1)
 
 #%% call_args_kwargs_type,barebones
 def foo(*args: float, **kwargs: int):
     print(args, kwargs, args.__class__.__name__)
 
-foo(1, f=1)  #: (1) (f: 1) Tuple[float]
+foo(1, f=1)  #: (1,) (f: 1) Tuple[float]
 foo(1, 2.1, 3, z=2)  #: (1, 2.1, 3) (z: 2) Tuple[float,float,float]
 
 def sum(x: Generator[int]):
@@ -517,7 +517,7 @@ foo(1, 2, 3)
 #: a (1, 2, 3)
 #: k (x: 1)
 foo(1, 2, 3, 4)
-#: 1 2 3 (4) ()
+#: 1 2 3 (4,) ()
 #: a (1, 2, 4, 3)
 #: k (x: 1)
 foo(1, 2, zamboni=3)

test/parser/typecheck_stmt.codon

@@ -235,7 +235,7 @@ print foo(N=1, x=2.0) #: 1.41421
 print foo(N=1, x=(1, 'bar')) #: foo: bar
 print foo(N=1, x=(1, 2)) #: len 2
 print foo(N=3, x=(1, 2)) #: ()
-print foo(N=1, x=(1, 2, 3)) #: (3)
+print foo(N=1, x=(1, 2, 3)) #: (3,)
 
 #%% try_throw,barebones
 class MyError(Static[Exception]):

test/parser/types.codon

@@ -940,9 +940,9 @@ print zoo(2, 3)
 print zoo('s', 3)
 #: decorating zoo[...,...,...]
 #: decorator (2, 3) ()
-#: zoo: 5, 2, (3)
+#: zoo: 5, 2, (3,)
 #: decorator ('s', 3) ()
-#: zoo: 5, s, (3)
+#: zoo: 5, s, (3,)
 
 def mydecorator(func):
     def inner():
@@ -1154,13 +1154,13 @@ call(foo)
 
 def foo(a:int, *b: float): return f"{a}_{b}", a+b[0]
 call(foo)
-#: ('1_(2)', 3)
+#: ('1_(2,)', 3)
 
 def call(f: Callable[[int,int],str]):
     print(f(1, 2))
 def foo(a: int, *b: int, **kw): return f"{a}_{b}_{kw}"
 call(foo(zzz=1.1, ...))
-#: 1_(2)_(zzz: 1.1)
+#: 1_(2,)_(zzz: 1.1)
 
 #%% traits_error,barebones
 def t[T](x: T, key: Optional[Callable[[T], S]] = None, S: type = NoneType):