| 
									
										
											  
											
												prefer Python 3 to Python 2 for running Spack
The Python landscape is going to be changing in 2020, and Python 2 will
be end of life. Spack should *prefer* Python 3 to Python 2 by default,
but we still need to run on systems that only have Python2 available.
This is trickier than it sounds, as on some systems, the `python` command
is `python2`; on others it's `python3`, and RHEL8 doesn't even have the
`python` command.  Instead, it makes you choose `python3` or
`python2`. You can thus no longer make a simple shebang to handle all the
cases.
This commit makes the `spack` script bilingual.  It is still valid
Python, but its shebang is `#!/bin/sh`, and it has a tiny bit of shell
code at the beginning to pick the right python and execute itself with
what it finds.
This has a lot of advantages.  I think this will help ensure that Spack
works well in Python3 -- there are cases where we've missed things
because Python2 is still the default `python` on most systems.  Also,
with this change, you do not lose the ability to execute the `spack`
script directly with a python interpreter.  This is useful for forcing
your own version of python, running coverage tools, and running profiling
tools.  i.e., these will not break with this change:
```console
$ python2 $(which spack) <args>
$ coverage run $(which spack) <args>
$ pyinstrument $(which spack) <args>
```
These would not work if we split `spack` into a python file and a shell
script (see #11783).  So, this gives us the best of both worlds.  We get
to control our interpreter *and* remain a mostly pure python executable.
											
										 
											2019-09-28 20:59:02 -07:00
										 |  |  | #!/bin/sh | 
					
						
							|  |  |  | # -*- python -*- | 
					
						
							| 
									
										
										
										
											2014-01-08 10:21:02 +01:00
										 |  |  | # | 
					
						
							| 
									
										
										
										
											2019-12-30 22:36:56 -08:00
										 |  |  | # Copyright 2013-2020 Lawrence Livermore National Security, LLC and other | 
					
						
							| 
									
										
										
										
											2018-10-07 13:52:23 -07:00
										 |  |  | # Spack Project Developers. See the top-level COPYRIGHT file for details. | 
					
						
							| 
									
										
										
										
											2014-01-08 10:21:02 +01:00
										 |  |  | # | 
					
						
							| 
									
										
										
										
											2018-10-07 13:52:23 -07:00
										 |  |  | # SPDX-License-Identifier: (Apache-2.0 OR MIT) | 
					
						
							|  |  |  | 
 | 
					
						
							| 
									
										
											  
											
												prefer Python 3 to Python 2 for running Spack
The Python landscape is going to be changing in 2020, and Python 2 will
be end of life. Spack should *prefer* Python 3 to Python 2 by default,
but we still need to run on systems that only have Python2 available.
This is trickier than it sounds, as on some systems, the `python` command
is `python2`; on others it's `python3`, and RHEL8 doesn't even have the
`python` command.  Instead, it makes you choose `python3` or
`python2`. You can thus no longer make a simple shebang to handle all the
cases.
This commit makes the `spack` script bilingual.  It is still valid
Python, but its shebang is `#!/bin/sh`, and it has a tiny bit of shell
code at the beginning to pick the right python and execute itself with
what it finds.
This has a lot of advantages.  I think this will help ensure that Spack
works well in Python3 -- there are cases where we've missed things
because Python2 is still the default `python` on most systems.  Also,
with this change, you do not lose the ability to execute the `spack`
script directly with a python interpreter.  This is useful for forcing
your own version of python, running coverage tools, and running profiling
tools.  i.e., these will not break with this change:
```console
$ python2 $(which spack) <args>
$ coverage run $(which spack) <args>
$ pyinstrument $(which spack) <args>
```
These would not work if we split `spack` into a python file and a shell
script (see #11783).  So, this gives us the best of both worlds.  We get
to control our interpreter *and* remain a mostly pure python executable.
											
										 
											2019-09-28 20:59:02 -07:00
										 |  |  | # This file is bilingual. The following shell code finds our preferred python. | 
					
						
							|  |  |  | # Following line is a shell no-op, and starts a multi-line Python comment. | 
					
						
							|  |  |  | # See https://stackoverflow.com/a/47886254 | 
					
						
							|  |  |  | """:" | 
					
						
							|  |  |  | # prefer python3, then python, then python2 | 
					
						
							|  |  |  | for cmd in python3 python python2; do | 
					
						
							|  |  |  |    command -v > /dev/null $cmd && exec $cmd $0 "$@" | 
					
						
							|  |  |  | done | 
					
						
							|  |  |  | 
 | 
					
						
							|  |  |  | echo "==> Error: spack could not find a python interpreter!" >&2 | 
					
						
							|  |  |  | exit 1 | 
					
						
							|  |  |  | ":""" | 
					
						
							|  |  |  | # Line above is a shell no-op, and ends a python multi-line comment. | 
					
						
							|  |  |  | # The code above runs this file with our preferred python interpreter. | 
					
						
							|  |  |  | 
 | 
					
						
							| 
									
										
										
										
											2017-03-07 14:25:48 -08:00
										 |  |  | from __future__ import print_function | 
					
						
							|  |  |  | 
 | 
					
						
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										 |  |  | import os | 
					
						
							| 
									
										
										
										
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										 |  |  | import sys | 
					
						
							| 
									
										
										
										
											2017-05-08 13:18:29 -07:00
										 |  |  | 
 | 
					
						
							| 
									
										
										
										
											2017-03-07 09:31:15 -08:00
										 |  |  | if sys.version_info[:2] < (2, 6): | 
					
						
							| 
									
										
										
										
											2014-12-19 11:09:37 -08:00
										 |  |  |     v_info = sys.version_info[:3] | 
					
						
							| 
									
										
										
										
											2017-03-07 09:31:15 -08:00
										 |  |  |     sys.exit("Spack requires Python 2.6 or higher." | 
					
						
							| 
									
										
										
										
											2016-08-09 13:23:53 -07:00
										 |  |  |              "This is Python %d.%d.%d." % v_info) | 
					
						
							| 
									
										
										
										
											2013-02-13 17:50:44 -08:00
										 |  |  | 
 | 
					
						
							|  |  |  | # Find spack's location and its prefix. | 
					
						
							| 
									
										
										
										
											2017-05-08 13:18:29 -07:00
										 |  |  | spack_file = os.path.realpath(os.path.expanduser(__file__)) | 
					
						
							|  |  |  | spack_prefix = os.path.dirname(os.path.dirname(spack_file)) | 
					
						
							| 
									
										
										
										
											2013-02-13 17:50:44 -08:00
										 |  |  | 
 | 
					
						
							|  |  |  | # Allow spack libs to be imported in our scripts | 
					
						
							| 
									
										
										
										
											2017-05-08 13:18:29 -07:00
										 |  |  | spack_lib_path = os.path.join(spack_prefix, "lib", "spack") | 
					
						
							|  |  |  | sys.path.insert(0, spack_lib_path) | 
					
						
							| 
									
										
										
										
											2016-10-12 18:25:18 -07:00
										 |  |  | 
 | 
					
						
							|  |  |  | # Add external libs | 
					
						
							| 
									
										
										
										
											2017-05-08 13:18:29 -07:00
										 |  |  | spack_external_libs = os.path.join(spack_lib_path, "external") | 
					
						
							| 
									
										
										
										
											2018-01-16 07:00:39 +01:00
										 |  |  | 
 | 
					
						
							|  |  |  | if sys.version_info[:2] == (2, 6): | 
					
						
							|  |  |  |     sys.path.insert(0, os.path.join(spack_external_libs, 'py26')) | 
					
						
							|  |  |  | 
 | 
					
						
							| 
									
										
										
										
											2017-05-08 13:18:29 -07:00
										 |  |  | sys.path.insert(0, spack_external_libs) | 
					
						
							| 
									
										
										
										
											2013-02-13 17:50:44 -08:00
										 |  |  | 
 | 
					
						
							| 
									
										
										
										
											2018-11-07 01:06:18 +01:00
										 |  |  | # Here we delete ruamel.yaml in case it has been already imported from site | 
					
						
							|  |  |  | # (see #9206 for a broader description of the issue). | 
					
						
							|  |  |  | # | 
					
						
							|  |  |  | # Briefly: ruamel.yaml produces a .pth file when installed with pip that | 
					
						
							| 
									
										
										
										
											2019-05-18 21:00:46 -05:00
										 |  |  | # makes the site installed package the preferred one, even though sys.path | 
					
						
							| 
									
										
										
										
											2018-11-07 01:06:18 +01:00
										 |  |  | # is modified to point to another version of ruamel.yaml. | 
					
						
							|  |  |  | if 'ruamel.yaml' in sys.modules: | 
					
						
							|  |  |  |     del sys.modules['ruamel.yaml'] | 
					
						
							|  |  |  | 
 | 
					
						
							|  |  |  | if 'ruamel' in sys.modules: | 
					
						
							|  |  |  |     del sys.modules['ruamel'] | 
					
						
							|  |  |  | 
 | 
					
						
							| 
									
										
										
										
											2017-05-08 13:18:29 -07:00
										 |  |  | # Once we've set up the system path, run the spack main method | 
					
						
							|  |  |  | import spack.main  # noqa | 
					
						
							|  |  |  | sys.exit(spack.main.main()) |