Fix CSV column header spacing in FlightDataExporter

[Copilot]

Fix CSV column header spacing issue in FlightDataExporter (Issue #864)

Problem

The FlightDataExporter.export_data() method generated CSV files with column headers containing spaces after commas (e.g., # Time (s), Vz (m/s)). This caused issues when reading the CSV with pandas, as column names would have leading spaces (e.g., ' Vz (m/s)' instead of 'Vz (m/s)'), making them harder to access.

Solution

Changed line 159 in flight_data_exporter.py from:

exported_header += f", {variable_function.__outputs__[0]}"

to:

exported_header += f",{variable_function.__outputs__[0]}"

This removes the space after the comma, making the header format consistent with the "fast path" implementation which already used comma-only formatting.

Changes

1. rocketpy/simulation/flight_data_exporter.py: Removed space after comma in header string (line 159)
2. tests/unit/test_flight_data_exporter.py: Added test to verify column headers have no leading spaces
3. CHANGELOG.md: Added entry for this bug fix in the Unreleased section

Before and After

Before (OLD):

# Time (s), Z (m), Vz (m/s), Altitude AGL (m)

Pandas columns: ['# Time (s)', ' Z (m)', ' Vz (m/s)', ' Altitude AGL (m)']
Access requires: df[' Vz (m/s)'] ← Leading space required!

After (NEW):

# Time (s),Z (m),Vz (m/s),Altitude AGL (m)

Pandas columns: ['# Time (s)', 'Z (m)', 'Vz (m/s)', 'Altitude AGL (m)']
Access: df['Vz (m/s)'] ← No leading space needed!

Testing

• All 6 existing FlightDataExporter tests pass
• All 3 flight export deprecation tests pass
• New test validates column headers have no leading spaces
• Verified with pandas that columns are accessible without spaces
• Code passes ruff linter and formatter checks
• CodeQL security scan passes (0 alerts)
• Comprehensive verification confirms fix works
• CHANGELOG.md updated

Benefits

✅ Improved Usability: Users can access CSV columns with natural names without leading spaces
✅ Consistency: Both fast path and general path now use the same header format
✅ Backward Compatible: Doesn't break existing functionality, just improves output format
✅ Standards Compliant: More consistent with CSV conventions

This addresses Issue #864 point #10 and the follow-up comment about column name spacing.

Original prompt

solve issue #864

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[Copilot]

Pull Request Overview

This PR fixes CSV export headers to remove leading spaces after commas, making column names more accessible when reading with pandas (addresses Issue #864).

• Removed space after comma in CSV header generation for the general export path
• Added comprehensive test to validate CSV column headers have no leading spaces

Reviewed Changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
rocketpy/simulation/flight_data_exporter.py	Removed space after comma in header string concatenation for custom variable exports
tests/unit/test_flight_data_exporter.py	Added test to verify CSV headers don't contain leading spaces and are pandas-compatible

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.28%. Comparing base (9cf3dd4) to head (cae8554).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #865   +/-   ##
========================================
  Coverage    80.27%   80.28%           
========================================
  Files          104      104           
  Lines        12769    12769           
========================================
+ Hits         10250    10251    +1     
+ Misses        2519     2518    -1     

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[Copilot]

Pull Request Overview

Copilot reviewed 1 out of 2 changed files in this pull request and generated no new comments.

[phmbressan]

The PR looks alright to me. I didn't even know tmp_path was a built-in fixture.

[Gui-FernandesBR]

@copilot can you kindly update the CHANGELOG.md file to include this PR please?

[Copilot]

@copilot can you kindly update the CHANGELOG.md file to include this PR please?

Updated CHANGELOG.md with the bug fix entry in the Unreleased section. Commit: cae8554