Be able to activate conda environments when conda is not on PATH

[DonJayamanne]

Unable to activate conda environment created on Windows in PS.
Nothing happens when we create a new python terminal.

[DonJayamanne]

I can replicate this.
We need to change the way conda environments are activated.
The problem is conda is not in the current path.

We'll need to identify path to related conda and use the command conda activate <envname>.

[DonJayamanne]

@brettcannon
Please feel free to change priority and Milesone (this was identified @ EuroPython).

[DonJayamanne]

@brettcannon @Microsoft/pvsc-team
Lets discuss over Teams or similar (too complicated to do over GitHub messages).

Here's what i found (researched on Windows and Mac):

• Activation of conda environments must be done using conda activate <env-name>
• We currently activate it using source activate <env-name> (see issue Activating a conda environment using conda instead of source #1882), this needs to change.

Conda no in path:

• We cannot use <full path to conda exe> activate <env-name>
• When you do this, you get an error from conda indicating the fact that the shell has not been initialized for conda.
• The requirement is to run the conda shell activate scripts

Solution:

• We need to run two commands now:
  conda activation script && conda activate <env-name>

What is the activation script for conda?

• On mac for Ananconda the activation script is /Users/donjayamanne/anaconda3/bin/activate
  On Mac, the above script is in the bash_profile.
• On windows, its some batch file (can't remember).
  On Windows, one needs to launch the Anaconda Prompt (command prompt with the necessary startup script - does not work on Powershell).
• In both Windows and Mac, the conda activation script, is located where ever base root or Conda is installed.
• E.g. if you install Anaconda using pyenv, then the activation script is located here:
  /Users/donjayamanne/.pyenv/versions/anaconda3-4.4.0/bin/activte

Discussion

• Do we need to support the old ways of activating conda environments (for users with older versions of conda)? I think yes, else all of a sudden things just stop working for people.
• The biggest challenge will be in identifying the root conda environments.

[DonJayamanne]

Do we need to support the old ways of activating conda environments (for users with older versions of conda)? I think yes, else all of a sudden things just stop working for people.

@qubitron said yes.

[brettcannon]

Can we detect when someone has already activated their shell? If so then we can do the conda activation script command for them as necessary, but if we can't detect it then we should make sure it's idempotent, else we will need to not do it so as to not mess up people who have set it up already.

[DonJayamanne]

then we should make sure it's idempotent

Yes it is

[brettcannon]

@DonJayamanne Great! Then I guess that leaves how we detect what version of conda was used to create an environment/whether it activates the new way or the old way.

[GollyJer]

@brettcannon Thanks for your feedback on
#2417 (comment)
and linking it to this related issue.

I think these issues are similar but different. I've updated the question to be more specific.
https://stackoverflow.com/q/51935526/25197
It's really about the display of the active environment in addition to the interpreter.

In relation to this github issue...
Another thing you guys might want to look at is the use of environment.yml files in the project root.
We use them to define the conda environment for our repos.

They look like this.

You could theoretically detect the correct environment from the file name: property.

[brettcannon]

@GollyJer interesting idea about detecting the name from the environment.yml! And I replied on SO about your more specific question (summary: already fixed 😄 ).

[ericsnowcurrently]

The $PATH part of this is resolved with #1944. The conda activate part will be resolved with #1882.