Perforce. P4CONCIG is set, but Rider reports variables as "is not defined"

Problem

Can't establish connection to perforce server. p4config is set properly and all the variables should be discovered. But Rider doesn't resolve them:

Server unknown. P4PORT is not defined
Client unknown. P4CLIENT is not defined

Cause

Such an issue is likely to happen when you need to work in several workspaces simultaneously and trying to use per-workspace or per-project .p4config file. The issue is likely caused by specific setting in P4V client.

Resolution

• OpenP4V;
• Open the “Connection” tab;
• Open “Enviroment Settings…”;
• Untick the checkbox for “Use current connection for environment settings”;
• Click OK;
• Restart Rider;