Support filenames containing spaces

[chapulina]

File names and paths containing spaces have never been officially supported by Gazebo classic. There are use cases which are known to work, but because this has never been a well supported use case, there are corner cases that won't work, and there's also the possibility that new functionality breaks existing cases that happen to work.

This issue is about making the support for spaces in file names and paths official. Test cases will be added for all supported file types and ways of inserting them into simulation, to make sure they continue to be supported. In the process, the use cases which don't currently work will be fixed.

The following file types will support spaces:

• World files
  • From the command line: gazebo <world file>
• Model files
  • Through the ~/factory topic
  • Through the <include> SDF tag
  • From the GUI
• Mesh files (for visuals and collisions, DAE, OBJ, STL)
  • Referenced in SDF files
• Material files
  • Ogre material scrips referenced in SDF files
  • MTL files referenced in OBJ files (not supported, see material files containing spaces in their name cannot be read tinyobjloader/tinyobjloader#46)
• Normal map file
  • Referenced in SDF files
• Actor skins and animations
  • Referenced in SDF files
• Textures
  • Referenced in COLLADA files (Collada fails to find texture with space in file name #2369)
  • Referenced in MTL files
  • Referenced in material scripts

Notably, plugin files (shared libraries) are not included in this list.

[chapulina]

According to Ogre's documentation, textures in material scripts can't have spaces. As they gracefully put it:

"Note that the texture file cannot include spaces. Those of you Windows users who like spaces in filenames, please get over it and use underscores instead."

However, in my testing, I saw that spaces work not only on texture files, but also the material files themselves. At least on Linux. I added a test here: bd91bfd. If it fails on Windows, I'll disable the test there.

[chapulina]

I couldn't find an official OBJ specification. Looking around the internet, it seems that there isn't a consensus about whether spaces should be supported in files referenced from OBJ and MTL files, more specifically:

• MTL files referenced from OBJ files
• Texture files referenced from MTL files

Gazebo uses tinyobjloader, and that project made a conscious decision of not supporting files with spaces (tinyobjloader/tinyobjloader#46), because there are use cases where multiple files may be specified, and they're separated by spaces.

On the other hand, it looks like Meshlab supports spaces in these filenames through the VCGlib parser, see issue cnr-isti-vclab/meshlab#66, which I believe was fixed by this commit: cnr-isti-vclab/vcglib@c547c56.

Since Gazebo uses tinyobjloader and they have a good reason for not supporting spaces, I think Gazebo shouldn't support spaces in resources used by these files.

[chapulina]

OBJ / MTL

It turned out that textures referenced in MTL files were already working, so the only missing piece was referencing MTL files from OBJ.

I opened a PR against tinyobjloader to add support for escaping spaces in MTL files: tinyobjloader/tinyobjloader#285.. If that gets in and is released, I'll open a separate PR updating our internal fork of tinyobjloader to their latest 1.x tag.

[chapulina]

The last piece of the puzzle (MTL / OBJ) is on #2885.

[chapulina]

Solved by #2877 and #2885