The attached patch implements PEP-263. The following
differences to the PEP (rev. 1.8) are known:

• The implementation interprets "ASCII compatible" as
  meaning "bytes below 128 always denote ASCII
  characters", although this property is only used for
  ",', and \. There have been other readings of "ASCII
  compatible", so this should probably be elaborated in
  the PEP.

• The check whether all bytes follow the declared or
  system encoding (including comments and string
  literals) is only performed if the encoding is "ascii".

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A note on the implementation strategy: it turned out that
communicating the encoding into the abstract syntax was the
biggest challenge.

To solve this, I introduced encoding_decl pseudo node: it is
an unused non-terminal whose STR() is the encoding, and
whose only child is the true root of the syntax tree. As
such, it is the only non-terminal which has a STR value.

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Thank you !

I'll add a note to the PEP about the way the first two lines
are processed (removing the ASCII mention...).

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I've set the group to Python 2.3 so the priority has some
context (I'd rather you move the priority down to 5 but I
understand this is your personal priority).

I haven't accepted the PEP yet (although I expect I will),
so please don't check this in yet (if you feel it needs to
be saved in CVS, use a branch).

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Ok, I've had a look at the patch.

It looks good except for the overly
complicated implementation of the
unicode-escape codec.

Even though there's a bit of code duplication,
I'd prefer to have two separate functions here:
one for the standard char* pointer type and
another one for Py_UNICODE*, ie.

PyUnicode_DecodeUnicodeEscape(char*...)
and
PyUnicode_DecodeUnicodeEscapeFromUnicode(Py_UNICODE*...)

This is easier to support and gives better
performance since the compiler can optimize
the two functions making different
assumptions.

You'll also need to include a name mangling
at the top of the header for the new API.

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Changing the decoding functions will not result in one
additional function, but in two of them: you'll also get
PyUnicode_DecodeRawUnicodeEscapeFromUnicode.

That seems quite unmaintainable to me: any change now needs
to propagate into four functions. OTOH, I don't think that
the code that allows parsing a variable-sized strings is
overly complicated.

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Version 2 of this patch implements revision 1.11 of the PEP
(phase 1). The check of the complete source file for
compliance with the declared encoding is implemented by
decoding the input line-by-line; I believe that for all
supported encodings, this is not different compared to
decoding the entire source file at once.

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Apart from the codec changes, the patch looks ok.

I would still like two APIs for the two different codec tasks,
though. I don't expect anything much to change in the
codecs, so maintenance is not an issue.

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This patch has been superceded by 534304.