Error when parsing anchor names ending with underscore-number

[NightFurySL2001]

Anchors generated by FontLab when reading binary font files usually end with underscore-number, e.g. _t.uni3001_1. When passing these names generated by FontLab into fontmake, the builder fails as the anchor name with underscore-number are identified as the index of ligature component to attach to.

Traceback (most recent call last):
  File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 519, in _iter_compile
    yield compile_func(ufo, debugFeatureFile=debugFeatureFile, **options)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\site-packages\ufo2ft\__init__.py", line 117, in compileOTF
    return OTFCompiler(**kwargs).compile(ufo)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\site-packages\ufo2ft\_compilers\baseCompiler.py", line 65, in compile
    self.compileFeatures(ufo, font, glyphSet=glyphSet)
  File "C:\Python311\Lib\site-packages\ufo2ft\_compilers\baseCompiler.py", line 145, in compileFeatures
    otFont = featureCompiler.compile()
             ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\site-packages\ufo2ft\featureCompiler.py", line 148, in compile
    self.setupFeatures()
  File "C:\Python311\Lib\site-packages\ufo2ft\featureCompiler.py", line 315, in setupFeatures
    writer.write(self.ufo, featureFile, compiler=self)
  File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\baseFeatureWriter.py", line 151, in write
    self.setContext(font, feaFile, compiler=compiler)
  File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\markFeatureWriter.py", line 325, in setContext
    ctx.anchorLists = self._getAnchorLists()
                      ^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\markFeatureWriter.py", line 360, in _getAnchorLists
    a = self.NamedAnchor(name=anchorName, x=x, y=y)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\markFeatureWriter.py", line 177, in __init__
    isMark, key, number = parseAnchorName(
                          ^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\markFeatureWriter.py", line 151, in parseAnchorName
    raise ValueError("mark anchor cannot be numbered: %r" % anchorName)
ValueError: mark anchor cannot be numbered: '_t.uni0308_2'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Python311\Lib\site-packages\fontmake\__main__.py", line 746, in main
    project.run_from_ufos(
  File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 1374, in run_from_ufos
    self.build_otfs(ufos, cff_version=cff_version, inplace=inplace, **kwargs)
  File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 315, in build_otfs
    self.save_otfs(ufos, **kwargs)
  File "C:\Python311\Lib\site-packages\fontTools\misc\loggingTools.py", line 375, in wrapper
    return func(*args, **kwds)
           ^^^^^^^^^^^^^^^^^^^
  File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 682, in save_otfs
    for font, ufo in zip(fonts, ufos):
  File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 521, in _iter_compile
    raise FontmakeError("Compiling UFO failed", ufo.path) from e
fontmake.errors.FontmakeError: In 'orig-pearl-tangyuan-v2.ufo': Compiling UFO failed: mark anchor cannot be numbered: '_t.uni0308_2'

This convention is not noted anywhere in any formalised standards, and is only noted in parseAnchorName() function description of ufo2ft:

Parse anchor name and return a tuple that specifies:
1) whether the anchor is a "mark" anchor (bool);
2) the "key" name of the anchor, i.e. the name after stripping all the
prefixes and suffixes, which identifies the class it belongs to (str);
3) An optional number (int), starting from 1, which identifies that index
of the ligature component the anchor refers to.

The 'ignoreRE' argument is an optional regex pattern (str) identifying
sub-strings in the anchor name that should be ignored when parsing the
three elements above.

It is not mentioned in UFO specification:

name: An arbitrary name for the anchor. This attribute is optional. It must be at least one character long. There is no maximum name length. A name must not contain control characters.

and

Anchor naming conventions↩
The following are agreed upon standard naming conventions for special uses of the name attribute.

Ligature Carets↩
Anchors with a name starting with caret_ or vcaret_ indicate horizontal or vertical caret positions for ligature glyphs. Example usage would be to compile the OpenType GDEF Ligature Caret List table.

Anchor names starting with caret_ provide the x value for a ligature caret position, and the y value is ignored. Likewise, anchor names starting with vcaret_ provide the y value for a ligature caret position, and the x value is ignored.

Both names may be followed arbitrary text (caret_1, caret_blah, etc) for designers or applications to have unique caret position names.

There must be exactly N-1 caret positions for N ligature components.

Or in AFDKO FEA syntax:

The anchor name follows the same rules as are used to form glyph names. For example:

anchorDef 300 0 ANCHOR_1;
anchorDef 120 -20 contourpoint 5 ANCHOR_2;