x.py build: error: XZ support is required to download LLVM

[Walther]

Steps:

• Follow instructions at https://rustc-dev-guide.rust-lang.org/getting-started.html
• git clone https://github.com/rust-lang/rust.git (at commit e38fb30 )
• git submodule update --init --recursive
• ./x.py setup, select b) compiler: Contribute to the compiler or rustdoc
• ./x.py build

./x.py build
Updating only changed submodules
Submodules updated in 0.14 seconds
error: XZ support is required to download LLVM
help: consider disabling `download-ci-llvm` or using python3
Build completed unsuccessfully in 0:00:00

Both python and python3 exist

which python
/usr/bin/python

which python3
/usr/bin/python3

Note:

rust/x.py

Line 1 in e38fb30

#!/usr/bin/env python

# Running the same command defaults to python 2 on the OS
/usr/bin/env python
Python 2.7.16 (default, Oct 10 2019, 22:02:15)
[GCC 8.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.

Environment: WSL2 Debian 10 buster

cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux 10 (buster)"
NAME="Debian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
VERSION_CODENAME=buster
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

uname -a
Linux matcha 4.4.0-19041-Microsoft #488-Microsoft Mon Sep 01 13:43:00 PST 2020 x86_64 GNU/Linux

Workaround:

python3 x.py build

---

Three thoughts:

• Should x.py be smarter about python vs python3 detection & execution, to fix this without user action?
• Should the error message be improved, in a way that helps a user to work around this? (for example, "python3 detected, edit x.py to use python3 instead" or other suggestion)
• Should the contribution guide have an updated mention of python3 requirement? Currently: "Most notably, you will need Python 2 or 3 to run x.py."

[Walther]

Additional note: on a server with a Ubuntu 20.04 focal fossa installation, where python is not even present:

./x.py setup
/usr/bin/env: ‘python’: No such file or directory

which python
python not found

which python3
/usr/bin/python3

cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04.1 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.1 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal

[cuviper]

See also #71818 and #80625 -- cc @jyn514

[Walther]

Ah my bad, was searching with the full error and didn't find those two. Closing as duplicate 👍

[jyn514]

There is not a good way to fix #71818 (see https://rust-lang.zulipchat.com/#narrow/stream/122651-general/topic/x.2Epy.20.2B.20download-ci-llvm.20-.3E.20explicit.20python3.20needed.3F/near/221414355 for more discussion). #80625 should be merged as soon as I rebase it.

[willus10245]

I'm getting this error, even when calling python3 ./x.py check

[jyn514]

@willus10245 it's unlikely it's the same error - can you open a new issue with the full output of x.py?

[willus10245]

The error is identical to the original post on this issue

$ python3 x.py check
Updating only changed submodules
Submodules updated in 0.06 seconds
error: XZ support is required to download LLVM
help: consider disabling `download-ci-llvm` or using python3
Build completed unsuccessfully in 0:00:00

[willus10245]

@jyn514 do you mean the contents of x.py?

[willus10245]

@jyn514 opened #85476