sage.libs.singular: Do not fail if the Singular binary is not in PATH

[mkoeppe]

This code from #29024

    os.environ["SINGULAR_BIN_DIR"] = dirname(which("Singular"))

assumes that Singular is in PATH

This causes errors when users attempt to use sagelib outside of the environment set up by sage-env.

https://groups.google.com/g/sage-support/c/XBxpl-JjaNU/m/FtRvcoW0AgAJ

Depends on #31292
Depends on #31296

CC: @orlitzky @dimpase @koffie

Component: refactoring

Author: Matthias Koeppe

Branch/Commit: 4cd3130

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/33440

[mkoeppe]

comment:1

Fix should be via sage.features / #31296

[mkoeppe]

Dependencies: #31292, #31296

[orlitzky]

comment:3

We have this problem in a lot of packages and we usually usesage_confto store one of two values: the system location, or the sage location -- depending on what's detected at ./configure time. The spkg-configure.m4 for singular already detects SINGULAR_BIN; we probably just need to record its dirname() if it's not in the system's PATH.

[mkoeppe]

comment:4

I don't know if we need it as a configuration variable because the configure script just searches for it in PATH.

[orlitzky]

comment:5

Replying to @mkoeppe:

I don't know if we need it as a configuration variable because the configure script just searches for it in PATH.

The SAGE_LOCAL location will be prepended to PATH during ./configure though, so that's the time to write it down. Then later the location is known regardless of what PATH contains.

[orlitzky]

comment:6

Replying to @orlitzky:

The SAGE_LOCAL location will be prepended to PATH during ./configure though, so that's the time to write it down. Then later the location is known regardless of what PATH contains.

Sorry, that's half nonsense. If we don't find Singular in the PATH, we know that it's in the SAGE_LOCAL location, and we put that value into sage_conf so that later we don't need to rely on PATH.

[mkoeppe]

Branch: u/mkoeppe/sage_libs_singular__do_not_fail_if_the_singular_binary_is_not_in_path

[orlitzky]

Commit: f44f426

[orlitzky]

comment:8

I know you know this already, but I think adding geographically varied runtime checks for things that are known at build time is the wrong solution.

---

New commits:

6a63fa0	src/sage/features/singular.py: New
f44f426	src/sage/libs/singular/singular.pyx: Use sage.features.singular, do not fail on FeatureNotPresentError

[sagetrac-git]

Changed commit from f44f426 to 13649b8

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

32ce831	sage.features.Executable.absolute_path: New
88860d3	sage.features.Executable.absolute_path: If SAGE_LOCAL != SAGE_VENV, search first in SAGE_VENV/bin, SAGE_LOCAL/bin, then PATH
fb00b68	Merge #31296
13649b8	src/sage/interfaces/singular.py: Use sage.features.singular.Singular().absolute_path()

[mkoeppe]

comment:10

No objection if you want to provide SINGULAR_BIN via sage_conf

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

8801359	src/sage/features/__init__.py: Fix import
403bcc1	sage.features.Executable: Fix up
16bc8dd	src/sage/features/singular.py: New
97c4eb4	src/sage/libs/singular/singular.pyx: Use sage.features.singular, do not fail on FeatureNotPresentError
09f710f	src/sage/interfaces/singular.py: Use sage.features.singular.Singular().absolute_path()
9ed65d8	src/sage/features/singular.py: Fix doctest output

[sagetrac-git]

Changed commit from 13649b8 to 9ed65d8

[mkoeppe]

comment:12

Replying to @mkoeppe:

No objection if you want to provide SINGULAR_BIN via sage_conf

This variable would be used in src/sage/features/singular.py

[mkoeppe]

Author: Matthias Koeppe, ...

[sagetrac-git]

Changed commit from 9ed65d8 to 727ec53

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

8bb7e3a	src/sage/features/__init__.py: Relax doctest
9fad95e	Merge #31292
727ec53	Merge #31296

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

001f92a	configure, pkgs/sage-conf, sage.env, sage.features.singular: Handle SINGULAR_BIN
a2a061c	src/sage/features/singular.py: Fix up doctest output

[sagetrac-git]

Changed commit from 727ec53 to a2a061c

[mkoeppe]

Changed author from Matthias Koeppe, ... to Matthias Koeppe

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

a93e9af	src/sage/features/__init__.py: Simplify Executable.absolute_path
5b25c1d	sage.features: Refactor StaticFile, Executable through a new base class FileFeature
6c35717	sage.features.FileFeature: Replace method absolute_path by absolute_filename, with deprecation
9266709	Merge #31292
ffead1d	Merge #31296
4cd3130	sage.interfaces.singular, sage.libs.singular: Use Singular().absolute_filename()

[sagetrac-git]

Changed commit from a2a061c to 4cd3130

[mkoeppe]

comment:18

Let's get this in please

[dimpase]

comment:19

How does one test this? I tried the way given in the link, but it ends up as follows:

ima@hilbert /mnt/opt/Sage $ ./sage-dev/sage -python3 -m venv --system-site-packages venv
dima@hilbert /mnt/opt/Sage $ source venv/bin/activate
(venv) dima@hilbert /mnt/opt/Sage $ python3
Python 3.9.10 (main, Mar  4 2022, 14:46:20) 
[GCC 11.2.1 20211127] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from sage.all import *
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'sage'
>>> 

Am I doing something wrong?

[mkoeppe]

comment:20

The method of setting up the venv that was tried in that post only works when Sage has built its own Python. One cannot make a venv from a venv.

[mkoeppe]

comment:21

You can test it by just using command lines like the ones I showed in #31296

[dimpase]

Reviewer: Dima Pasechnik

[dimpase]

comment:22

OK, this works.

[mkoeppe]

comment:23

Thank you!

[vbraun]

Changed branch from u/mkoeppe/sage_libs_singular__do_not_fail_if_the_singular_binary_is_not_in_path to 4cd3130