refactor: simplify register_unit_format to avoid in function imports …

…and better interplay with registry

pint/delegates/formatter/_spec_helpers.py

@@ -29,6 +29,8 @@
 _PRETTY_EXPONENTS = "⁰¹²³⁴⁵⁶⁷⁸⁹"
 _JOIN_REG_EXP = re.compile(r"{\d*}")
 
+REGISTERED_FORMATTERS: dict[str, Any] = {}
+
 
 def parse_spec(spec: str) -> str:
     """Parse and return spec.
@@ -39,16 +41,12 @@ def parse_spec(spec: str) -> str:
     - what happens if two distinct values are found?
 
     """
-    # TODO: provisional
-    from ...formatting import _ORPHAN_FORMATTER
-
-    _FORMATTERS = _ORPHAN_FORMATTER._formatters
 
     result = ""
     for ch in reversed(spec):
         if ch == "~" or ch in _BASIC_TYPES:
             continue
-        elif ch in list(_FORMATTERS.keys()) + ["~"]:
+        elif ch in list(REGISTERED_FORMATTERS.keys()) + ["~"]:
             if result:
                 raise ValueError("expected ':' after format specifier")
             else:
@@ -93,18 +91,12 @@ def extract_custom_flags(spec: str) -> str:
 
     (i.e those not part of Python's formatting mini language)
     """
-    import re
 
     if not spec:
         return ""
 
-    # TODO: provisional
-    from ...formatting import _ORPHAN_FORMATTER
-
-    _FORMATTERS = _ORPHAN_FORMATTER._formatters
-
     # sort by length, with longer items first
-    known_flags = sorted(_FORMATTERS.keys(), key=len, reverse=True)
+    known_flags = sorted(REGISTERED_FORMATTERS.keys(), key=len, reverse=True)
 
     flag_re = re.compile("(" + "|".join(known_flags + ["~"]) + ")")
     custom_flags = flag_re.findall(spec)
@@ -118,12 +110,7 @@ def remove_custom_flags(spec: str) -> str:
     (i.e those not part of Python's formatting mini language)
     """
 
-    # TODO: provisional
-    from ...formatting import _ORPHAN_FORMATTER
-
-    _FORMATTERS = _ORPHAN_FORMATTER._formatters
-
-    for flag in sorted(_FORMATTERS.keys(), key=len, reverse=True) + ["~"]:
+    for flag in sorted(REGISTERED_FORMATTERS.keys(), key=len, reverse=True) + ["~"]:
         if flag:
             spec = spec.replace(flag, "")
     return spec

pint/delegates/formatter/_to_register.py

@@ -10,10 +10,7 @@
 
 from typing import TYPE_CHECKING, Callable
 from ...compat import ndarray, np, Unpack
-from ._spec_helpers import (
-    split_format,
-    join_mu,
-)
+from ._spec_helpers import split_format, join_mu, REGISTERED_FORMATTERS
 
 from ..._typing import Magnitude
 
@@ -55,11 +52,9 @@ def format_custom(unit, registry, **options):
         f"{u:custom}"
     """
 
-    from ...formatting import _ORPHAN_FORMATTER
-
     # TODO: kwargs missing in typing
     def wrapper(func: Callable[[PlainUnit, UnitRegistry], str]):
-        if name in _ORPHAN_FORMATTER._formatters:
+        if name in REGISTERED_FORMATTERS:
             raise ValueError(f"format {name!r} already exists")  # or warn instead
 
         class NewFormatter:
@@ -112,6 +107,6 @@ def format_quantity(
                     self.format_unit(quantity.units, uspec, **babel_kwds),
                 )
 
-        _ORPHAN_FORMATTER._formatters[name] = NewFormatter()
+        REGISTERED_FORMATTERS[name] = NewFormatter()
 
     return wrapper

pint/delegates/formatter/full.py

@@ -21,6 +21,7 @@
 from .latex import LatexFormatter, SIunitxFormatter
 from .plain import RawFormatter, CompactFormatter, PrettyFormatter, DefaultFormatter
 from ._format_helpers import BabelKwds
+from ._to_register import REGISTERED_FORMATTERS
 
 if TYPE_CHECKING:
     from ...facets.plain import PlainQuantity, PlainUnit, MagnitudeT
@@ -75,10 +76,8 @@ def get_formatter(self, spec: str):
             if k in spec:
                 return v
 
-        from ...formatting import _ORPHAN_FORMATTER
-
         try:
-            return _ORPHAN_FORMATTER._formatters[spec]
+            return REGISTERED_FORMATTERS[spec]
         except KeyError:
             pass
 
@@ -200,3 +199,15 @@ def format_quantity_babel(
             length=length or self.babel_length,
             locale=locale or self.locale,
         )
+
+
+################################################################
+# This allows to format units independently of the registry
+#
+REGISTERED_FORMATTERS["raw"] = RawFormatter()
+REGISTERED_FORMATTERS["D"] = DefaultFormatter()
+REGISTERED_FORMATTERS["H"] = HTMLFormatter()
+REGISTERED_FORMATTERS["P"] = PrettyFormatter()
+REGISTERED_FORMATTERS["Lx"] = SIunitxFormatter()
+REGISTERED_FORMATTERS["L"] = LatexFormatter()
+REGISTERED_FORMATTERS["C"] = CompactFormatter()

pint/formatting.py

@@ -12,7 +12,6 @@
 
 
 # Backwards compatiblity stuff
-from .delegates.formatter import Formatter
 from .delegates.formatter.latex import (
     vector_to_latex,  # noqa
     matrix_to_latex,  # noqa
@@ -33,15 +32,11 @@
     extract_custom_flags,  # noqa
     remove_custom_flags,  # noqa
     split_format,  # noqa
+    REGISTERED_FORMATTERS,
 )  # noqa
 from .delegates.formatter._to_register import register_unit_format  # noqa
 
 
-# TODO: This will be gone soon.
-
-_ORPHAN_FORMATTER = Formatter()
-
-
 def format_unit(unit, spec: str, registry=None, **options):
     # registry may be None to allow formatting `UnitsContainer` objects
     # in that case, the spec may not be "Lx"
@@ -56,7 +51,7 @@ def format_unit(unit, spec: str, registry=None, **options):
         spec = "D"
 
     if registry is None:
-        _formatter = _ORPHAN_FORMATTER._formatters.get(spec, None)
+        _formatter = REGISTERED_FORMATTERS.get(spec, None)
     else:
         try:
             _formatter = registry._formatters[spec]

pint/testsuite/test_unit.py

@@ -138,7 +138,8 @@ def test_unit_formatting_snake_case(self, subtests):
                 assert f"{x}" == result, f"Failed for {spec}, {result}"
 
     def test_unit_formatting_custom(self, monkeypatch):
-        from pint import formatting, register_unit_format
+        from pint import register_unit_format
+        from pint.delegates.formatter._spec_helpers import REGISTERED_FORMATTERS
 
         @register_unit_format("new")
         def format_new(unit, *args, **options):
@@ -148,7 +149,7 @@ def format_new(unit, *args, **options):
 
         assert f"{ureg.m:new}" == "new format"
 
-        del formatting._ORPHAN_FORMATTER._formatters["new"]
+        del REGISTERED_FORMATTERS["new"]
 
     def test_ipython(self):
         alltext = []