[YAML] Allow constants and simple comparisons in generic expressions.

[robertwb]

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[robertwb]

R: @Polber

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[robertwb]

The Java WindowedWordCountIT failures look unrelated.

[Polber]

Overall, looks really good - my one concern is the clunkiness of string literals... I know that YAML treats everything as a string, so you need some way of emphasizing when an expression should be treated as a string literal, but specifying '"some string"' feels messy. Is there a way to modify the SafeLineLoader to preserve explicit double quotes?

Something like https://stackoverflow.com/a/67917266 perhaps

[Polber]

nit: Should this message refer to expression rather than input fields?

Suggested change

	f"Missing language specification or unknown input fields: {expr}")
	f"Missing language specification or invalid generic expression: {expr}")

[robertwb]

Fixed. I kept the "unkown input fields" as a missing/typo input name is still a quite likely error here we should point to.

[Polber]

FYI all of the test files have this error, so not sure what is generating this license, but it appears to not like single quotes

Suggested change

	# (the# Row(word='License'); you may not use this file except in compliance with
	# the License. You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an# Row(word='AS IS' BASIS,
	# (the "License"); you may not use this file except in compliance with
	# the License. You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,

[robertwb]

Fixed here and #31480 for the rest.

[robertwb]

Overall, looks really good - my one concern is the clunkiness of string literals... I know that YAML treats everything as a string, so you need some way of emphasizing when an expression should be treated as a string literal, but specifying '"some string"' feels messy. Is there a way to modify the SafeLineLoader to preserve explicit double quotes?

I agree that it's a bit clunky, but I do want the value to be a string that contains quotes in it as a literal. Shouldn't be too common, and it's what I would also use if I was specifying an explicit language.

Something like https://stackoverflow.com/a/67917266 perhaps

This seems to be about preserving the quoting style in writing, but it seems dangerous to treat 'possible_var' and "possible_var" differently in parsing.

[robertwb]

Addressed comments, PTAL.

[codecov]

Codecov Report

Attention: Patch coverage is 73.68421% with 15 lines in your changes missing coverage. Please review.

Project coverage is 71.15%. Comparing base (bb4ad99) to head (5c16329).
Report is 46 commits behind head on master.

❗ Current head 5c16329 differs from pull request most recent head e41b014

Please upload reports for the commit e41b014 to get more accurate results.

Files	Patch %	Lines
sdks/python/apache_beam/yaml/yaml_mapping.py	72.22%	15 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #31455      +/-   ##
============================================
+ Coverage     71.14%   71.15%   +0.01%     
  Complexity     3008     3008              
============================================
  Files          1055     1055              
  Lines        133439   133434       -5     
  Branches       3248     3248              
============================================
+ Hits          94929    94948      +19     
+ Misses        35382    35358      -24     
  Partials       3128     3128              

Flag	Coverage Δ
python	81.30% <73.68%> (+0.01%)	⬆️

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[robertwb]

Any more thoughts on this?

[Polber]

Any more thoughts on this?

I agree with your comments above - I still think it's clunky, but I agree the use-case is limited and this way it is more explicit.

I think biggest thing is to add documentation and possibly adjusting the error message to point out that the expression should include single quotes around a double quoted string for string literals (which could be displayed only if regex does not match it to a number).

[robertwb]

I added a section to the documentation and referred to that in the error message.