feat(stdlib): add datetime module bindings (#267)

* feat(stdlib): add datetime module bindings

Adds F# bindings for the Python datetime module, covering:
- timedelta (duration with days/seconds/microseconds, total_seconds())
- date (year/month/day, isoformat, strftime, weekday, fromisoformat, replace)
- time (hour/minute/second/microsecond, isoformat, strftime, fromisoformat)
- datetime (full date+time, now, utcnow, fromisoformat, strptime, combine, timestamp, astimezone)
- timezone (fixed-offset tzinfo, utc singleton)

Each class has a separate static factory type (timedeltaStatic, dateStatic,
timeStatic, datetimeStatic, timezoneStatic) for constructors and class methods.
Int arguments use int($1) Emit wrappers to handle Fable's Int32 boxing.

Adds 30 tests covering all bound classes and their main operations.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* refactor(stdlib): rework datetime bindings, fix justfile, apply fantomas

Datetime:
- Switch from paired static-factory types to Queue.fs-style primary-ctor
  classes. The original factory pattern combined [<Emit("$0($1...)")>] with
  [<NamedParams>], which silently dropped all kwargs (generated timedelta()
  instead of timedelta(days=3.0)).
- timedelta: empty primary ctor plus static ofDays/ofHours/ofMinutes/
  ofSeconds/ofWeeks/ofMilliseconds/ofMicroseconds factories with float()
  emit wrappers so Fable's Float64 doesn't reach Python's datetime. Added
  add/sub/neg arithmetic.
- timezone: moved above datetime so datetime.astimezone/now(tz)/
  fromtimestamp(tz) can take timezone instead of obj.
- date/time/datetime: collapsed replaceDate/replaceTime into a single
  [<NamedParams>] replace that supports partial replacement (any subset of
  fields). Added time.replace.
- datetime: arithmetic via sub(datetime)->timedelta, sub(timedelta)->
  datetime, add(timedelta)->datetime. utcnow marked [<Obsolete>] pointing
  at now(tz = timezone.utc).
- Module-level doc note about the `time` identifier collision with
  Fable.Python.Time.
- Tests expanded from 30 to 37 covering partial replace, arithmetic,
  datetime.now(tz), and the ofX factories.

justfile:
- Drop -r from `dotnet fantomas` invocations in `format` and `format-check`;
  fantomas has no -r flag and it caused both recipes to fail.

Other files: fantomas reformatting applied by `just format` to pre-existing
files touched by the formatter.

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

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Dag Brattli <dag@brattli.net>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 4 people

justfile

@@ -83,13 +83,13 @@ shipit *args:
 
 # Format code with Fantomas
 format:
-    dotnet fantomas {{src_path}} -r
-    dotnet fantomas {{test_path}} -r
+    dotnet fantomas {{src_path}}
+    dotnet fantomas {{test_path}}
 
 # Check code formatting without making changes
 format-check:
-    dotnet fantomas {{src_path}} -r --check
-    dotnet fantomas {{test_path}} -r --check
+    dotnet fantomas {{src_path}} --check
+    dotnet fantomas {{test_path}} --check
 
 # Install .NET tools (Fable, Fantomas) and Python dependencies
 setup:

src/Fable.Python.fsproj

@@ -25,6 +25,7 @@
     <Compile Include="stdlib/Os.fs" />
     <Compile Include="stdlib/Heapq.fs" />
     <Compile Include="stdlib/Itertools.fs" />
+    <Compile Include="stdlib/Datetime.fs" />
     <Compile Include="stdlib/Functools.fs" />
     <Compile Include="stdlib/Queue.fs" />
     <Compile Include="stdlib/String.fs" />

src/fable/Testing.fs

@@ -47,7 +47,7 @@ let throwsError (expected: string) (f: unit -> 'a) : unit =
 let throwsErrorContaining (expected: string) (f: unit -> 'a) : unit =
     match run f with
     | Error _ when String.IsNullOrEmpty expected -> ()
-    | Error (actual: string) when actual.Contains expected -> ()
+    | Error(actual: string) when actual.Contains expected -> ()
     | Error actual -> equal (sprintf "Error containing '%s'" expected) actual
     | Ok _ -> equal (sprintf "Error containing '%s'" expected) "No error was thrown"
 

src/stdlib/Builtins.fs

@@ -353,7 +353,8 @@ let __name__: string = nativeOnly
 let print obj = builtins.print obj
 
 /// Return the value of the named attribute of object with a default.
-let getattr obj name defaultValue = builtins.getattr (obj, name, defaultValue)
+let getattr obj name defaultValue =
+    builtins.getattr (obj, name, defaultValue)
 
 /// Sets the named attribute on the given object to the specified value.
 let setattr obj name value = builtins.setattr (obj, name, value)

src/stdlib/Datetime.fs

@@ -84,10 +84,12 @@ type IExports =
     /// Return True if the values a and b are close to each other
     /// See https://docs.python.org/3/library/math.html#math.isclose
     abstract isclose: a: float * b: float -> bool
+
     /// Return True if the values a and b are close to each other with custom tolerances
     /// See https://docs.python.org/3/library/math.html#math.isclose
     [<NamedParams(fromIndex = 2)>]
     abstract isclose: a: float * b: float * ?rel_tol: float * ?abs_tol: float -> bool
+
     /// Return the least common multiple of the integers
     /// See https://docs.python.org/3/library/math.html#math.lcm
     abstract lcm: [<ParamArray>] ints: int[] -> int

src/stdlib/Math.fs

@@ -34,10 +34,12 @@ type Queue<'T>() =
     /// operation goes into an uninterruptible wait on an underlying lock. This means that no exceptions can occur, and
     /// in particular a SIGINT will not trigger a KeyboardInterrupt.
     member x.get(?block: bool, ?timeout: float) : 'T = nativeOnly
+
     /// Equivalent to get(False).
     /// See https://docs.python.org/3/library/queue.html#queue.Queue.get_nowait
     [<Emit("$0.get_nowait()")>]
     member x.get_nowait() : 'T = nativeOnly
+
     /// Blocks until all items in the queue have been gotten and processed.
     ///
     /// The count of unfinished tasks goes up whenever an item is added to the queue. The count goes down whenever a
@@ -74,6 +76,7 @@ type SimpleQueue<'T>() =
     member x.put(item: 'T, ?block: bool, ?timeout: float) : unit = nativeOnly
     /// Remove and return an item from the queue.
     member x.get(?block: bool, ?timeout: float) : 'T = nativeOnly
+
     /// Equivalent to get(False).
     [<Emit("$0.get_nowait()")>]
     member x.get_nowait() : 'T = nativeOnly

src/stdlib/Queue.fs

@@ -32,6 +32,7 @@
     <Compile Include="TestSys.fs" />
     <Compile Include="TestTime.fs" />
     <Compile Include="TestString.fs" />
+    <Compile Include="TestDatetime.fs" />
     <Compile Include="TestPydantic.fs" />
     <Compile Include="TestFastAPI.fs" />
     <Compile Include="TestTypes.fs" />