07/08: doc: Note that `guix shell` should contain base language packages.

[guix-commits]

jpoiret pushed a commit to branch master
in repository guix.

commit 9f68a2a9c41166ec5ac24c082bcd96c433dd2ede
Author: Josselin Poiret <dev@jpoiret.xyz>
AuthorDate: Thu Mar 30 22:42:10 2023 +0200

    doc: Note that `guix shell` should contain base language packages.
    
    * doc/guix.texi (Invoking guix shell): Explain that python must be included 
in
    the invocation even if it is already available in the external environment.
    
    Suggested-by: Skyler <skyvine@protonmail.com>
---
 doc/guix.texi | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index c60e0b87b2..6105195bd9 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -96,7 +96,7 @@ Copyright @copyright{} 2021 Domagoj Stolfa@*
 Copyright @copyright{} 2021 Hui Lu@*
 Copyright @copyright{} 2021 pukkamustard@*
 Copyright @copyright{} 2021 Alice Brenon@*
-Copyright @copyright{} 2021, 2022 Josselin Poiret@*
+Copyright @copyright{} 2021-2023 Josselin Poiret@*
 Copyright @copyright{} 2021, 2023 muradm@*
 Copyright @copyright{} 2021, 2022 Andrew Tropin@*
 Copyright @copyright{} 2021 Sarah Morgensen@*
@@ -6271,6 +6271,14 @@ building or downloading any missing package, and runs the
 guix shell python python-numpy -- python3
 @end example
 
+Note that it is necessary to include the main @code{python} package in
+this command even if it is already installed into your environment.
+This is so that the shell environment knows to set @env{PYTHONPATH} and
+other related variables.  The shell environment cannot check the
+previously installed environment, because then it would be
+non-deterministic.  This is true for most libraries: their corresponding
+language package should be included in the shell invocation.
+
 @quotation Note
 @cindex shebang, for @command{guix shell}
 @command{guix shell} can be also be used as a script interpreter, also