feat(cli): add option --multiline

Thanks to @alexvoss for suggesting how to implement this
with current TOML Kit.

Author: dbohdan

README.md

@@ -134,9 +134,9 @@ uv tool install https://github.com/remarshal-project/remarshal
 
 ```none
 usage: remarshal [-h] [-v] [-f {cbor,json,msgpack,toml,yaml}] [-i <input>]
-                 [--indent <n>] [-k] [--max-values <n>] [-o <output>] [-s]
-                 [-t {cbor,json,msgpack,python,toml,yaml}] [--unwrap <key>]
-                 [--verbose] [--width <n>] [--wrap <key>]
+                 [--indent <n>] [-k] [--max-values <n>] [--multiline <n>]
+                 [-o <output>] [-s] [-t {cbor,json,msgpack,python,toml,yaml}]
+                 [--unwrap <key>] [--verbose] [--width <n>] [--wrap <key>]
                  [--yaml-style {,',",|,>}]
                  [input] [output]
 
@@ -158,6 +158,8 @@ options:
                         keys and null values for TOML
   --max-values <n>      maximum number of values in input data (default
                         1000000, negative for unlimited)
+  --multiline <n>       minimum number of items to make non-nested TOML array
+                        multiline (default 6)
   -o, --output <output>
                         output file
   -s, --sort-keys       sort JSON, Python, and TOML keys instead of preserving
@@ -286,7 +288,7 @@ $ curl -f 'https://archive-api.open-meteo.com/v1/era5?latitude=50.43&longitude=3
   ;
 latitude = 50.439365
 longitude = 30.476192
-generationtime_ms = 0.04208087921142578
+generationtime_ms = 0.03254413604736328
 utc_offset_seconds = 0
 timezone = "GMT"
 timezone_abbreviation = "GMT"
@@ -297,14 +299,65 @@ time = "iso8601"
 temperature_2m = "°C"
 
 [hourly]
-time = ["2014-10-05T00:00", "2014-10-05T01:00", "2014-10-05T02:00", "2014-10-05T03:00", "2014-10-05T04:00", "2014-10-05T05:00", "2014-10-05T06:00", "2014-10-05T07:00", "2014-10-05T08:00", "2014-10-05T09:00", "2014-10-05T10:00", "2014-10-05T11:00", "2014-10-05T12:00", "2014-10-05T13:00", "2014-10-05T14:00", "2014-10-05T15:00", "2014-10-05T16:00", "2014-10-05T17:00", "2014-10-05T18:00", "2014-10-05T19:00", "2014-10-05T20:00", "2014-10-05T21:00", "2014-10-05T22:00", "2014-10-05T23:00"]
-temperature_2m = [5.7, 5.3, 5.0, 4.8, 4.6, 4.6, 7.0, 8.9, 10.8, 12.2, 13.3, 13.9, 13.9, 13.7, 13.3, 12.3, 11.1, 10.2, 9.4, 8.5, 8.2, 7.9, 8.0, 7.8]
+time = [
+    "2014-10-05T00:00",
+    "2014-10-05T01:00",
+    "2014-10-05T02:00",
+    "2014-10-05T03:00",
+    "2014-10-05T04:00",
+    "2014-10-05T05:00",
+    "2014-10-05T06:00",
+    "2014-10-05T07:00",
+    "2014-10-05T08:00",
+    "2014-10-05T09:00",
+    "2014-10-05T10:00",
+    "2014-10-05T11:00",
+    "2014-10-05T12:00",
+    "2014-10-05T13:00",
+    "2014-10-05T14:00",
+    "2014-10-05T15:00",
+    "2014-10-05T16:00",
+    "2014-10-05T17:00",
+    "2014-10-05T18:00",
+    "2014-10-05T19:00",
+    "2014-10-05T20:00",
+    "2014-10-05T21:00",
+    "2014-10-05T22:00",
+    "2014-10-05T23:00",
+]
+temperature_2m = [
+    5.7,
+    5.3,
+    5.0,
+    4.8,
+    4.6,
+    4.6,
+    7.0,
+    8.9,
+    10.8,
+    12.2,
+    13.3,
+    13.9,
+    13.9,
+    13.7,
+    13.3,
+    12.3,
+    11.1,
+    10.2,
+    9.4,
+    8.5,
+    8.2,
+    7.9,
+    8.0,
+    7.8,
+]
 ```
 
-Remarshal does not limit the line width in TOML.
+Remarshal controls the number of items at which a TOML array becomes multiline,
+but it does not control the line width.
 You can use
 [`taplo fmt`](https://taplo.tamasfe.dev/cli/usage/formatting.html)
-to reformat the TOML and break up long lines with arrays.
+for finer TOML formatting.
 
 ## License
 

src/remarshal/main.py

@@ -30,6 +30,7 @@
 import cbor2  # type: ignore
 import colorama
 import tomlkit
+import tomlkit.items
 from rich_argparse import RichHelpFormatter
 
 try:
@@ -58,6 +59,8 @@ class Defaults:
     PYTHON_INDENT = 1
     YAML_INDENT = 2
 
+    MULTILINE_THRESHOLD = 6
+
     WIDTH = 80
 
 
@@ -97,6 +100,7 @@ class PythonOptions(FormatOptions):
 @dataclass(frozen=True)
 class TOMLOptions(FormatOptions):
     indent: int | None = Defaults.INDENT
+    multiline_threshold: int = Defaults.MULTILINE_THRESHOLD
     sort_keys: bool = Defaults.SORT_KEYS
     stringify: bool = Defaults.STRINGIFY
 
@@ -284,6 +288,18 @@ def _parse_command_line(argv: Sequence[str]) -> argparse.Namespace:
         ),
     )
 
+    parser.add_argument(
+        "--multiline",
+        default=Defaults.MULTILINE_THRESHOLD,
+        dest="multiline_threshold",
+        metavar="<n>",
+        type=int,
+        help=(
+            "minimum number of items to make non-nested TOML array multiline "
+            "(default %(default)s)"
+        ),
+    )
+
     output_group = parser.add_mutually_exclusive_group()
     output_group.add_argument("output", default="-", nargs="?", help="output file")
     output_group.add_argument(
@@ -688,6 +704,7 @@ def _encode_python(
 def _encode_toml(
     data: Mapping[Any, Any],
     *,
+    multiline_threshold: int,
     sort_keys: bool,
     stringify: bool,
 ) -> str:
@@ -709,14 +726,28 @@ def stringify_null(x: Any) -> Any:
     default_callback = stringify_null if stringify else reject_null
 
     try:
-        return tomlkit.dumps(
+        toml = tomlkit.item(
             traverse(
                 data,
                 key_callback=key_callback,
                 default_callback=default_callback,
             ),
-            sort_keys=sort_keys,
+            _sort_keys=sort_keys,
         )
+
+        def multilinify(item: tomlkit.items.Item) -> None:
+            match item:
+                case tomlkit.items.Array():
+                    if len(item) >= multiline_threshold:
+                        item.multiline(multiline=True)
+
+                case tomlkit.items.AbstractTable():
+                    for value in item.values():
+                        multilinify(value)
+
+        multilinify(toml)
+
+        return toml.as_string()
     except AttributeError as e:
         if str(e) == "'list' object has no attribute 'as_string'":
             msg = (
@@ -769,6 +800,7 @@ def format_options(
     output_format: str,
     *,
     indent: int | None = None,
+    multiline_threshold: int = Defaults.MULTILINE_THRESHOLD,
     sort_keys: bool = False,
     stringify: bool = False,
     width: int = Defaults.WIDTH,
@@ -797,6 +829,7 @@ def format_options(
 
         case "toml":
             return TOMLOptions(
+                multiline_threshold=multiline_threshold,
                 sort_keys=sort_keys,
                 stringify=stringify,
             )
@@ -824,12 +857,14 @@ def encode(
             if not isinstance(options, CBOROptions):
                 msg = "expected 'options' argument to have class 'CBOROptions'"
                 raise TypeError(msg)
+
             encoded = _encode_cbor(data)
 
         case "json":
             if not isinstance(options, JSONOptions):
                 msg = "expected 'options' argument to have class 'JSONOptions'"
                 raise TypeError(msg)
+
             encoded = _encode_json(
                 data,
                 indent=options.indent,
@@ -841,12 +876,14 @@ def encode(
             if not isinstance(options, MsgPackOptions):
                 msg = "expected 'options' argument to have class 'MsgPackOptions'"
                 raise TypeError(msg)
+
             encoded = _encode_msgpack(data)
 
         case "python":
             if not isinstance(options, PythonOptions):
                 msg = "expected 'options' argument to have class 'PythonOptions'"
                 raise TypeError(msg)
+
             encoded = _encode_python(
                 data,
                 indent=options.indent,
@@ -858,14 +895,17 @@ def encode(
             if not isinstance(options, TOMLOptions):
                 msg = "expected 'options' argument to have class 'TOMLOptions'"
                 raise TypeError(msg)
+
             if not isinstance(data, Mapping):
                 msg = (
                     f"Top-level value of type '{type(data).__name__}' cannot "
                     "be encoded as TOML"
                 )
                 raise TypeError(msg)
+
             encoded = _encode_toml(
                 data,
+                multiline_threshold=options.multiline_threshold,
                 sort_keys=options.sort_keys,
                 stringify=options.stringify,
             ).encode(UTF_8)
@@ -874,6 +914,7 @@ def encode(
             if not isinstance(options, YAMLOptions):
                 msg = "expected 'options' argument to have class 'YAMLOptions'"
                 raise TypeError(msg)
+
             encoded = _encode_yaml(
                 data,
                 indent=options.indent,
@@ -959,6 +1000,7 @@ def main() -> None:
         options = format_options(
             args.output_format,
             indent=args.indent,
+            multiline_threshold=args.multiline_threshold,
             sort_keys=args.sort_keys,
             stringify=args.stringify,
             width=args.width,

tests/multiline-3.toml

@@ -0,0 +1,32 @@
+foo = [
+    1,
+    2,
+    [3],
+    4,
+    5,
+]
+bar = [
+    1,
+    [2, 3, 4, 5, 6],
+    7,
+]
+
+[baz]
+qux = [
+    1,
+    2,
+    3,
+]
+quux = [
+    1,
+    2,
+    3,
+    4,
+]
+quuux = [
+    1,
+    2,
+    3,
+    4,
+    5,
+]

tests/multiline-5.toml

@@ -0,0 +1,19 @@
+foo = [
+    1,
+    2,
+    [3],
+    4,
+    5,
+]
+bar = [1, [2, 3, 4, 5, 6], 7]
+
+[baz]
+qux = [1, 2, 3]
+quux = [1, 2, 3, 4]
+quuux = [
+    1,
+    2,
+    3,
+    4,
+    5,
+]

tests/multiline.json

@@ -0,0 +1,9 @@
+{
+    "foo": [1, 2, [3], 4, 5],
+    "bar": [1, [2, 3, 4, 5, 6], 7],
+    "baz": {
+        "qux": [1, 2, 3],
+        "quux": [1, 2, 3, 4],
+        "quuux": [1, 2, 3, 4, 5]
+    }
+}

tests/multiline.toml

@@ -0,0 +1,7 @@
+foo = [1, 2, [3], 4, 5]
+bar = [1, [2, 3, 4, 5, 6], 7]
+
+[baz]
+qux = [1, 2, 3]
+quux = [1, 2, 3, 4]
+quuux = [1, 2, 3, 4, 5]

tests/test_remarshal.py

@@ -100,6 +100,7 @@ def _convert_and_read(  # noqa: PLR0913
     output_format: str,
     *,
     indent: int | None = None,
+    multiline_threshold: int = Defaults.MULTILINE_THRESHOLD,
     output_filename: str,
     sort_keys: bool = False,
     stringify: bool = False,
@@ -113,6 +114,7 @@ def _convert_and_read(  # noqa: PLR0913
     options = remarshal.format_options(
         output_format,
         indent=indent,
+        multiline_threshold=multiline_threshold,
         sort_keys=sort_keys,
         stringify=stringify,
         width=width,
@@ -221,6 +223,25 @@ def test_json2toml(self, convert_and_read) -> None:
         )
         assert output_sig == reference_sig
 
+    def test_json2toml_multiline_default(self, convert_and_read) -> None:
+        output = convert_and_read("multiline.json", "json", "toml")
+        reference = read_file("multiline.toml")
+        assert output == reference
+
+    def test_json2toml_multiline_3(self, convert_and_read) -> None:
+        output = convert_and_read(
+            "multiline.json", "json", "toml", multiline_threshold=3
+        )
+        reference = read_file("multiline-3.toml")
+        assert output == reference
+
+    def test_json2toml_multiline_5(self, convert_and_read) -> None:
+        output = convert_and_read(
+            "multiline.json", "json", "toml", multiline_threshold=5
+        )
+        reference = read_file("multiline-5.toml")
+        assert output == reference
+
     def test_json2yaml(self, convert_and_read) -> None:
         output = convert_and_read("example.json", "json", "yaml").decode("utf-8")
         reference = read_file("example.yaml").decode("utf-8")