Robot's get_link_names throws exception for group with one link

[beverlylytle]

Describe the bug
Robot's get_link_names throws exception for group with one link

To Reproduce
Steps to reproduce the behavior:

1. Load the ur5 demo robot.
2. Run the following code:

try:
    # If testing with the released versions of compas_fab up to 1.0.2, this code will run
    from compas_fab.robots.ur5 import Robot
    robot = Robot()
except:
    # if testing with the main branch (unreleased), this one will do instead
    from compas_fab.robots import RobotLibrary
    robot = RobotLibrary.ur5()

names = robot.get_link_names(group="endeffector")
print(names)

Expected behavior
names should equal ['ee_link']

Actual behavior
Exception is thrown "Exception: No chain found between the specified element"

[kaniket7209]

Hey @gonzalocasas I want to start my contribution in this good first issue .

[utam-1]

Hi @gonzalocasas, will you assign this issue to me? I have just began learning about open source.

[gonzalocasas]

Hi @gonzalocasas, will you assign this issue to me? I have just began learning about open source.

Done! Thanks!!!

[gonzalocasas]

I will update the example code to the latest version because the one on the description is very old

[gonzalocasas]

I've updated the snippet of code that will cause this bug to make it easier to reproduce. If you have problems while trying to fix this, feel free to post questions here!

[annapurna-gupta]

Hi @gonzalocasas ,

I just submitted a PR that addresses an issue with the get_link_names method in the compas_fab library. This fix allows the method to handle groups containing only one link without throwing exceptions.

Could you please take a look when you have a moment? Your feedback would be greatly appreciated!

Thank you!

[gonzalocasas]

hi @annapurna-gupta ! sorry it took quite long, but I've finally added feedback to your PR. Please feel free to rework and push your updated, and I will re-review
cheers

[gonzalocasas]

(btw, looking at the description I understand why you wrote the test like that, but that was just an example piece of code, not how a unit test is supposed to be written)

[Swastik-Verma]

Hi @gonzalocasas ,

I'd like to work on this issue — I've already looked into it a bit and think I can fix it. Could you please assign it to me?

[Swastik-Verma]

Hi @gonzalocasas @beverlylytle ,

Following up on my comment above — I've gone ahead and opened a pull request (#465) that fixes this issue. It adds a check in get_link_names() for the single-link group case, along with a regression test. Would appreciate a review when you have a chance. Thanks!