RDISCROWD-7364 custom task export fields

[n00rsy]

Issue number of the reported bug or feature request: RDISCROWD-7364

Describe your changes

• Update task csv export: when display_info_columns is in the request body, filter the task__info fields to only contain fields in display_info_columns.

Testing performed
tested locally

[coveralls]

Pull Request Test Coverage Report for Build 11600690507

Details

• 15 of 16 (93.75%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.001%) to 94.015%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pybossa/exporter/task_csv_export.py	2	3	66.67%

Totals
Change from base Build 11559628491:	-0.001%
Covered Lines:	17374
Relevant Lines:	18480

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💛 - Coveralls

[dchhabda]

cosmetic; indentation to be corrected here

[dchhabda]

For code clarity, we can add a variable for number here

[dchhabda]

See if following changes makes sense considering comments mentioned above

def filter_table_headers(headers, filtered_columns):
  accepted_task_info_fields = set(filtered_columns) if filtered_columns else set()
  task_info_header = "task__info__"
  task_info_header_len = len(task_info_header)

  for header in headers:
    if header != 'task__info':
      if header.startswith(task_info_header):
        masked_header = header[task_info_header_len:]  
        if masked_header in accepted_task_info_fields:  
            new_headers.append(header)  
      else:  
        new_headers.append(header) 

[dchhabda]

pass can be avoided w/ flipping the condition

[n00rsy]

if we switch to

if header != 'task__info':
 ...
else:  
     new_headers.append(header) 

task__info will always get added to new_headers.

[n00rsy]

For clarity, there are 3 cases for each header:

1. header = 'task__info', so we skip it
2. header is like 'task__info__[fieldname], so we check fieldname against accepted fields set and add accordingly
3. header is something else, so we add it to the new_headers list (task__id, task__state, etc)

[dchhabda]

Likely due to small tab space, it was not clear that else part of if header != 'task__info': won't be adding new_header always.

[dchhabda]

Upon making this changes, PR can be merged. Thanks!