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Concurrently detect the minimum Python versions needed to run code

Project description

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Vermin

Concurrently detect the minimum Python versions needed to run code. Additionally, since the code is vanilla Python, and it doesn’t have any external dependencies, it works with v2.7+ and v3+.

It functions by parsing Python code into an abstract syntax tree (AST), which it traverses and matches against internal dictionaries with 1205 rules, covering v2.0-2.7 and v3.0-3.8, divided into 131 modules, 852 classes/functions/constants members of modules, 193 kwargs of functions, 4 strftime directives, 2 array typecodes, 3 codecs error handler names, and 20 codecs encodings. Including looking for v2/v3 print expr and print(expr), long, f-strings, self-documenting f-strings, coroutines (async and await), asynchronous generators (await and yield in same function), asynchronous comprehensions, await in comprehensions, boolean constants, named expressions, positional-only parameters, yield from, exception context cause (raise .. from ..), dict comprehensions, infix matrix multiplication, "..".format(..), imports (import X, from X import Y, from X import *), function calls wrt. name and kwargs, strftime + strptime directives used, and function, function and variable annotations, continue in finally block, modular inverse pow(), array typecodes, codecs error handler names and encodings. It tries to detect and ignore user-defined functions, classes, arguments, and variables with names that clash with library-defined symbols.

The project is fairly well-tested with 1314 unit and integration tests.

Usage

It is fairly straightforward to use Vermin:

./vermin.py /path/to/your/project

Or via PyPi:

% pip install vermin
% vermin /path/to/your/project

When using continuous integration (CI) tools, like Travis CI, Vermin can be used to check that the minimum required versions didn’t change. The following is an exerpt:

install:
- ./setup_virtual_env.sh
- pip install vermin
script:
- vermin -t=2.7 -t=3 project_package otherfile.py

Examples

% ./vermin.py
Vermin 0.8.0
Usage: ./vermin.py [options] <python source files and folders..>

Options:
  -q    Quite mode. It only prints the final versions verdict.
  -v..  Verbosity level 1 to 4. -v, -vv, -vvv, and -vvvv shows increasingly more
        information.
        -v     will show the individual versions required per file.
        -vv    will also show which modules, functions etc. that constitutes
               the requirements.
        -vvv   will also show line/col numbers.
        -vvvv  will also show user-defined symbols being ignored.
  -t=V  Target version that files must abide by. Can be specified once or twice.
        If not met Vermin will exit with code 1.
  -p=N  Use N concurrent processes to analyze files (defaults to all cores = 8).
  -i    Ignore incompatible version warnings.
  -l    Lax mode: ignores conditionals (if, ternary, for, while, try, bool op) on AST
        traversal, which can be useful when minimum versions are detected in
        conditionals that it is known does not affect the results.
  -d    Dump AST node visits.

  --hidden
        Analyze 'hidden' files and folders starting with '.' (ignored by default).

  --versions
        In the end, print all unique versions required by the analysed code.

  [--exclude <name>] ...
        Exclude full names, like 'email.parser.FeedParser', from analysis. Useful to
        ignore conditional logic that can trigger incompatible results. It's more fine
        grained than lax mode.

        Examples:
          Exclude 'foo.bar.baz' module/member: --exclude 'foo.bar.baz'
          Exclude 'foo' kwarg:                 --exclude 'somemodule.func(foo)'
          Exclude 'bar' codecs error handler:  --exclude 'ceh=bar'
          Exclude 'baz' codecs encoding:       --exclude 'ce=baz'

  [--exclude-file <file name>] ...
        Exclude full names like --exclude but from a specified file instead. Each line
        constitues an exclusion with the same format as with --exclude.

Results interpretation:
  ~2       No known reason it won't work with py2.
  !2       It is known that it won't work with py2.
  2.5, !3  Works with 2.5+ but it is known it won't work with py3.
  ~2, 3.4  No known reason it won't work with py2, works with 3.4+

% ./vermin.py -q vermin
Minimum required versions: 2.7, 3.0

% ./vermin.py -q -t=3.3 vermin
Minimum required versions: 2.7, 3.0
Target versions not met:   3.3
% echo $?
1

% ./vermin.py -q --versions vermin
Minimum required versions: 2.7, 3.0
Version range:             2.0, 2.2, 2.5, 2.7, 3.0

% ./vermin.py -v examples
Detecting python files..
Analyzing 6 files using 8 processes..
             /path/to/examples/formatv2.py
2.7, 3.2     /path/to/examples/argparse.py
2.7, 3.0     /path/to/examples/formatv3.py
2.0, 3.0     /path/to/examples/printv3.py
!2, 3.4      /path/to/examples/abc.py
             /path/to/examples/unknown.py
Minimum required versions:   3.4
Incompatible versions:         2

% ./vermin.py -vv /path/to/examples/abc.py
Detecting python files..
Analyzing using 8 processes..
!2, 3.4      /path/to/examples/abc.py
  'abc' requires (2.6, 3.0)
  'abc.ABC' requires (None, 3.4)

Minimum required versions: 3.4
Incompatible versions:     2

% ./vermin.py -vvv /path/to/examples/abc.py
Detecting python files..
Analyzing using 8 processes..
!2, 3.4      /path/to/examples/abc.py
  L1 C7: 'abc' requires (2.6, 3.0)
  L2: 'abc.ABC' requires (None, 3.4)

Minimum required versions: 3.4
Incompatible versions:     2

Lax Mode

Vermin parses Python source code into abstract syntax trees (ASTs) which it traverses to do analysis. However, it doesn’t do conditional logic, i.e. deciding which branches will be taken at runtime, since it can cause unexpected side-effects to actually evaluate code. As an example, analysis of the following:

if False:
  print(f"..but I won't be evaluated")

Will yield “f-strings require 3.6+” even though the branch will not be evaluated at runtime.

The lax mode, via argument -l, was created to circumvent cases like this. But it’s not a perfect solution since it will skip all if, ternarys, for, while, try, and boolean operations. Therefore it is recommended to run with and without lax mode to get a better understanding of individual cases.

Analysis Exclusions

Another approach to conditional logic than lax mode, is to exclude modules, members, kwargs, codecs error handler names, or codecs encodings by name from being analysed via argument --exclude <name> (multiple can be specified). Consider the following code block that checks if PROTOCOL_TLS is an attribute of ssl:

import ssl
tls_version = ssl.PROTOCOL_TLSv1
if hasattr(ssl, "PROTOCOL_TLS"):
  tls_version = ssl.PROTOCOL_TLS

It will state that “‘ssl.PROTOCOL_TLS’ requires (2.7, 3.6)” but to exclude that from the results, use --exclude 'ssl.PROTOCOL_TLS'. Afterwards, only “‘ssl’ requires (2.6, 3.0)” will be shown and the final minimum required versions are v2.6 and v3.0 instead of v2.7 and v3.6.

Code can even be excluded on a more fine grained level using the # novermin or # novm comments at line level. The following yields the same behavior as the previous code block, but only for that particular if and its body:

import ssl
tls_version = ssl.PROTOCOL_TLSv1
if hasattr(ssl, "PROTOCOL_TLS"):  # novermin
  tls_version = ssl.PROTOCOL_TLS

Contributing

Contributions are very welcome, especially adding and updating detection rules of modules, functions, classes etc. to cover as many Python versions as possible. For PRs, make sure to keep the code vanilla Python and run make test first. Note that code must be remain valid and working on Python v2.7+ and v3+.

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