Add support for producing multiline arrays

Author: sdispater

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Change Log
 
+## [Unreleased]
+
+### Added
+
+- Added support for producing multiline arrays
+
+
 ## [0.5.7] - 2019-10-04
 
 ### Fixed

tests/test_items.py

@@ -173,6 +173,29 @@ def test_array_behaves_like_a_list():
     )
 
 
+def test_array_multiline():
+    t = item([1, 2, 3, 4, 5, 6, 7, 8])
+    t.multiline(True)
+
+    expected = """\
+[
+    1,
+    2,
+    3,
+    4,
+    5,
+    6,
+    7,
+    8,
+]"""
+
+    assert expected == t.as_string()
+
+    t = item([])
+
+    assert "[]" == t.as_string()
+
+
 def test_dicts_are_converted_to_tables():
     t = item({"foo": {"bar": "baz"}})
 

tomlkit/items.py

@@ -744,14 +744,15 @@ class Array(Item, list):
     An array literal
     """
 
-    def __init__(self, value, trivia):  # type: (list, Trivia) -> None
+    def __init__(self, value, trivia, multiline=False):  # type: (list, Trivia) -> None
         super(Array, self).__init__(trivia)
 
         list.__init__(
             self, [v.value for v in value if not isinstance(v, (Whitespace, Comment))]
         )
 
         self._value = value
+        self._multiline = multiline
 
     @property
     def discriminant(self):  # type: () -> int
@@ -773,8 +774,23 @@ def is_homogeneous(self):  # type: () -> bool
 
         return len(set(discriminants)) == 1
 
+    def multiline(self, multiline):  # type: (bool) -> self
+        self._multiline = multiline
+
+        return self
+
     def as_string(self):  # type: () -> str
-        return "[{}]".format("".join(v.as_string() for v in self._value))
+        if not self._multiline:
+            return "[{}]".format("".join(v.as_string() for v in self._value))
+
+        s = "[\n" + self.trivia.indent + " " * 4
+        s += (",\n" + self.trivia.indent + " " * 4).join(
+            v.as_string() for v in self._value if not isinstance(v, Whitespace)
+        )
+        s += ",\n"
+        s += "]"
+
+        return s
 
     def append(self, _item):  # type: () -> None
         if self._value: