ParseElement.copy() result refers to previous instance #612
Description
Hi
I have come across a problem that seems to be caused by ParseElement.copy(). Not sure though if this should be a bug or if there is an easy way to fix it.
Here are the steps to reproduce
import pyparsing as pp
custom_id = pp.pyparsing_common.identifier.copy().set_name("custom identifer")
custom_id.parse_string("1")
This produces exception:
Traceback (most recent call last):
File "d:\misc\practice\dsl\halo-test\pyparsing\bug.prompt.py", line 7, in <module>
custom_id.parse_string("1")
File "D:\programs\miniconda3\envs\python310\lib\site-packages\pyparsing\core.py", line 1216, in parse_string
raise exc.with_traceback(None)
pyparsing.exceptions.ParseException: Expected identifier, found '1' (at char 0), (line:1, col:1)
Note that it should say "Expected custom identifier". However the following code behaves correctly:
import pyparsing as pp
custom_id = pp.Word(pp.identchars, pp.identbodychars).set_name("custom identifer")
custom_id.parse_string("1")
The little debugging I could do seems to show that the parseImpl overwritten in the constructor remains the same after copy(). You can test this by:
print(custom_id.parseImpl.__self__)
This prints identifier.
Due to this if I use set_results_name, it will also produce unexpected results.
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