non-package rosdep keys

[Noam-Dori]

as expected, some rosdep keys are not packages (for example, cmake, eigen). These need to be tracked using the ROS git, preferably automatically and without relying on commands. If a dependency links to one of these rosdep keys, it should not mark it as an error, somehow.

This is the list of rosdep keys and what they resolve to:

https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/base.yaml
https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/python.yaml
https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/ruby.yaml

You can read files directly from the internet or download them per version and read them there, or try to decipher the .pickle files available on the computer in ~/.ros/rosdep/sources.cache

caching could also be possible.

[Noam-Dori]

Strategy:

• There will be a new project-level component called ROSDepKeyCache that will be responsible for handling rosdep keys that are not handled directly by ROSPackageManager
• The cache may have initial values for common keys (like boost, cmake, eigen, opencv). This list, if it exists, may be updated in the future depending on user input.
• To get the rest on the keys, the cache will attempt to connect to the internet and read the rosdep files mentioned above. If it suceeds, the values are parsed and stored in the cache for use.
• the cache also stores whether or not it suceeded in fetching the files.
• the cached keys will be in the form of class ROSDepKey which inherits from ROSPackage for polymorphism (and potentially from ROSCompiledPackage). This class has a unique icon but will not resolve to any folder similar to the orphan package.
• the main exposed API of the cache is to:
  1. fetch the keys. If the offline database was never loaded, it will first load that and ONLY that (always suceeds). If the fetch failed and internet connection was never attempted, it will attempt to cache from the internet.
  2. check if there was ever internet connection.
  3. force a key cache from the internet.
  4. save a used key into the offline database.
• Key fetches currently only happen during autocompletion and dependency resolution, which trigger when either editing a manifest file or when one of the dependencies does not resolve. This happens to minimize internet connections.
• If there was no internet connection and a dependency does not resolve, a new intention will be added to try to force a new cache. This intention is available as long as there was no internet connection.
• forcing a new cache could always be triggered from the ROS settings page using a new button, no matter the internet connectivity.
• If a key is either resolved to or chosen from the autocompletion (might be redundent), the key is saved into an offline database that will be loaded the next time the user open the IDE (saving precious internet connections)