fix(pipenv): keep activation and the project directory in sync (#14021)

* fix(pipenv): don't activate or leak errors when virtualenv is missing

* fix(pipenv): compare whole path components when deactivating

$PWD
$pipfile_dir is a string-prefix test, so moving from a project to an
unrelated sibling whose path merely starts with the same text (…/proj ->
…/proj-archive, …/projX) does not deactivate: the project's virtualenv
stays active in a directory that has no Pipfile. Require an exact match or
a component boundary instead. Subdirectories of the project keep their
current behaviour, and a project at / still matches everything.

plugins/pipenv/pipenv.plugin.zsh

@@ -56,19 +56,26 @@ if zstyle -T ':omz:plugins:pipenv' auto-shell; then
     # deactivate shell if Pipfile doesn't exist and not in a subdir
     if [[ ! -f "$PWD/Pipfile" ]]; then
       if [[ "$PIPENV_ACTIVE" == 1 ]]; then
-        if [[ "$PWD" != "$pipfile_dir"* ]]; then
+        # Compare whole path components: `$pipfile_dir"*` also matches unrelated
+        # siblings that merely start with the same text (…/proj -> …/proj-docs),
+        # which would keep the virtualenv active outside the project.
+        local project_dir="${pipfile_dir%/}"
+        if [[ "$PWD" != "$project_dir" && "$PWD" != "$project_dir"/* ]]; then
           unset PIPENV_ACTIVE pipfile_dir
           deactivate
         fi
       fi
     fi
 
-    # activate the shell if Pipfile exists
+    # activate the shell if Pipfile exists and its virtualenv is usable
     if [[ "$PIPENV_ACTIVE" != 1 ]]; then
       if [[ -f "$PWD/Pipfile" ]]; then
-        export pipfile_dir="$PWD"
-        source "$(pipenv --venv)/bin/activate"
-        export PIPENV_ACTIVE=1
+        local venv_path
+        if venv_path="$(pipenv --venv 2>/dev/null)" && [[ -n "$venv_path" && -f "$venv_path/bin/activate" ]]; then
+          export pipfile_dir="$PWD"
+          source "$venv_path/bin/activate"
+          export PIPENV_ACTIVE=1
+        fi
       fi
     fi
   }