fix(map_loader): fix warnings with single point cloud map metadata

[xmfcx]

Description

Part of:

• Reduce excessive error and warning logs on Autoware launch #5539

Right now, even when we create a metadata with a single pcd, we receive "Create PCD metadata, as the pointcloud is a single file." warning from pointcloud_map_loader.

But it should throw the warning if there is no metadata but there is no metadata at all.

I've reordered the logic structure so:
In order:

1. if metadata exists -> use new method
2. if not, but only 1 pcd -> use exceptional method and warn
3. if not -> throw warning (no metadata)

cc. @ahmeddesokyebrahim

Tests performed

Help appreciated.

Effects on system behavior

Not applicable.

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[xmfcx]

I don't have a multi pcd map to test this.

@kminoda could you test this with a multi pcd map?

I can test it with single pcd map with and without metadata.

[ahmeddesokyebrahim]

@xmfcx That sounds great!!
I do really appreciate the amazing support and collaboration from your side. 👍

[codecov]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (a10f9c4) 14.88% compared to head (fd00125) 14.88%.

Files	Patch %	Lines
...intcloud_map_loader/pointcloud_map_loader_node.cpp	0.00%	8 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6384   +/-   ##
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  Coverage   14.88%   14.88%           
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  Files        1838     1838           
  Lines      126708   126707    -1     
  Branches    38042    38040    -2     
=======================================
  Hits        18865    18865           
+ Misses      86544    86542    -2     
- Partials    21299    21300    +1     

Flag	Coverage Δ		*Carryforward flag
differential	26.65% <0.00%> (?)
total	14.88% <ø> (+<0.01%)	⬆️	Carriedforward from a10f9c4

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[kminoda]

@xmfcx Hi, thank you for the PR. Unfortunately I am no longer a Perception team, so let me redirect this to Localization/Mapping team in TIER IV.

@Motsu-san @YamatoAndo Hi, would you check this?

[SakodaShintaro]

Thank you for the pull request.

I have confirmed the following scenarios:

• Single pcd with and without metadata: logging_simulator with sample map and sample rosbag
  • Works fine without log messages
• Multi-PCD with metadata: AWSIM on divided nishishinjuku map
  • Works fine
• Multi-pcd without metadata: AWSIM on divided nishishinjuku map
  • Outputs error logs properly (but only to the screen)
  • [Error] [1707783487.253310648] [map.pointcloud_map_loader]: PCD metadata file not found

I also don't think it's a problem from a code review perspective. Thank you for your improvement.

[Additional Note] If you want a divided map, you can use one provided as a sample or manually divide map using pointcloud_divider.

https://autowarefoundation.github.io/autoware-documentation/main/how-to-guides/others/using-divided-map/