# [PyCalVer: Automatic CalVer Versioning for Python Packages][repo_ref]

PyCalVer is a simple calendar based versioning system. With a single
`pycalver bump` command it will:

 - Automatically update version strings across files in your project.
 - Commit those changes and tag the commit with the new version.

Version strings generated by pycalver are compatible with python
packaging software
[setuptools](https://setuptools.readthedocs.io/en/latest/setuptools.html#specifying-your-project-s-version>)
[PEP440](https://www.python.org/dev/peps/pep-0440/).


Project/Repo:

[![MIT License][license_img]][license_ref]
[![Supported Python Versions][pyversions_img]][pyversions_ref]
[![PyCalVer v201809.0002-beta][version_img]][version_ref]
[![PyPI Releases][pypi_img]][pypi_ref]
[![PyPI Downloads][downloads_img]][downloads_ref]

Code Quality/CI:

[![Type Checked with mypy][mypy_img]][mypy_ref]
[![Code Style: sjfmt][style_img]][style_ref]
[![Code Coverage][codecov_img]][codecov_ref]
[![Build Status][build_img]][build_ref]


|            Name            |        role       |  since  | until |
|----------------------------|-------------------|---------|-------|
| Manuel Barkhau (@mbarkhau) | author/maintainer | 2018-09 | -     |


<!--
  To update the TOC:
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  $ md_toc -i gitlab README.md
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[](TOC)

  - [Introduction](#introduction)
      - [Format](#format)
      - [Versioning Behaviour](#versioning-behaviour)
      - [Lexical Ids](#lexical-ids)
  - [Usage](#usage)
      - [Configuration](#configuration)
      - [Bump It Up](#bump-it-up)
      - [Pattern Search and Replacement](#pattern-search-and-replacement)
  - [Rational](#rational)
      - [Other Versioning Software](#other-versioning-software)
      - [Some Details](#some-details)
      - [Realities of Version Numbers](#realities-of-version-numbers)
      - [Should I use PyCalVer for my Project?](#should-i-use-pycalver-for-my-project)
      - [Marketing/Vanity](#marketing-vanity)
      - [Rational](#rational-1)
      - [Breaking Things is a Big Deal](#breaking-things-is-a-big-deal)
      - [A Word on Marketing](#a-word-on-marketing)
      - [Commitment to Compatibility](#commitment-to-compatibility)
      - [The Life of a Library](#the-life-of-a-library)
      - [FAQ](#faq)

[](TOC)


## Introduction

The PyCalVer package provides the `pycalver` command to generate
version strings. The version strings have three parts:

```

    o Year and Month of Build
    |       o Sequential Build Number
    |       |      o Release Tag (optional)
    |       |      |
 ---+---  --+--  --+--
 v201812  .0123  -beta


```

Some examples:

```
v201711.0001-alpha
v201712.0027-beta
v201801.0031
v201801.0032-post
...
v202207.18133
v202207.18134
```

### Version String Format

The format for PyCalVer version strings can be parsed with this
regular expression:

```python
import re

# https://regex101.com/r/fnj60p/10
PYCALVER_PATTERN = r"""
\b
(?P<version>
    (?P<calver>
       v                        # "v" version prefix
       (?P<year>\d{4})
       (?P<month>\d{2})
    )
    (?P<build>
        \.                      # "." build nr prefix
        \d{4,}
    )
    (?P<release>
        \-                      # "-" release prefix
        (?:alpha|beta|dev|rc|post)
    )?
)(?:\s|$)
"""
PYCALVER_RE = re.compile(PYCALVER_PATTERN, flags=re.VERBOSE)

version_str = "v201712.0001-alpha"
version_info = PYCALVER_RE.match(version_str).groupdict()

assert version_info == {
    "version" : "v201712.0001-alpha",
    "calver"  : "v201712",
    "year"    : "2017",
    "month"   : "12",
    "build"   : ".0001",
    "release" : "-alpha",
}

version_str = "v201712.0033"
version_info = PYCALVER_RE.match(version_str).groupdict()

assert version_info == {
    "version" : "v201712.0033",
    "calver"  : "v201712",
    "year"    : "2017",
    "month"   : "12",
    "build"   : ".0033",
    "release" : None,
}
```

### Versioning Behaviour

To see how version strings are incremented, we can use
`pycalver incr`:

```shell
$ pip install pycalver
...
$ pycalver incr v201801.0033-beta
PyCalVer Version: v201809.0034-beta
PEP440 Version: 201809.34b0
```

This is the simple case:

 - The calendar component is update to the current year and month.
 - The build number is incremented by 1.
 - The optional release tag is preserved as is.

You can explicitly update the release tag using the
`--release=<tag>` argument:

```shell
$ pycalver incr v201801.0033-alpha --release=beta
PyCalVer Version: v201809.0034-beta
PEP440 Version: 201809.34b0
$ pycalver incr v201809.0034-beta --release=final
PyCalVer Version: v201809.0035
PEP440 Version: 201809.35
```

The version number is padded with extra zeros, to maintain the
lexical ordering of version numbers. What happens when the
padding is exhausted?

```shell
$ pycalver incr v201809.0999
PyCalVer Version: v201809.11000
PEP440 Version: 201809.11000
```

This is because the build number is generated as a sequence of
lexical ids.


### Lexical Ids

The build number padding may eventually be exhausted. In order to
preserve both lexical ordering, build numbers are incremented in
a special way. Examples will perhaps illustrate more clearly.

```python
"0001"
"0002"
"0003"
...
"0999"
"11000"
"11001"
...
"19998"
"19999"
"220000"
"220001"
```

What is happening here is that the left-most digit is incremented
early/preemptively. Whenever the left-most digit would change,
the padding of the id is expanded using this simple formula:

```python
prev_id = "0999"
next_id = str(int(prev_id, 10) + 1)           # "1000"
if prev_id[0] != next_id[0]:                  # "0" != "1"
    next_id = str(int(next_id, 10) * 11)      # 1000 * 11 = 11000
```

This behaviour ensures that the following semantic is always
preserved: `old_version < new_version`. This will be the case,
even if the padding was expanded and the version number was
incremented multiple times in the same month. To illustrate the
issue, imagine we did not expand the padding and instead just
incremented numerically.

```python
"0001"
"0002"
"0003"
...
"0999"
"1000"
...
"9999"
"10000"
```

Here we eventually run into a build number where the lexical
ordering is not preserved, since `"9999" < "10000" == False`.
This is a very rare corner case, but it's better to not have
to think about it.

Just as an example of why lexical ordering is a nice property to
have, there are lots of software which read git tags, but which
have no logic to parse version strings, which can nonetheless
order the version tags correctly.


## Usage

### Configuration

The fastest way to setup a project is to use `pycalver init`.


```shell
$ cd my-project
~/my-project$ pycalver init
Updated setup.cfg
```

This will add the something like the following to your
`setup.cfg` (depending on what files you have in your project):

```ini
[pycalver]
commit = True
tag = True
push = True

[pycalver:file_patterns]
setup.cfg =
    current_version = {version}
setup.py =
    "{version}",
    "{pep440_version}",
README.md =
    {version}
    {pep440_version}
```

This may or may not cover all version numbers across your
repository. Something like the following may illustrate
additional changes you might need to make.

```ini
[pycalver]
current_version = v201809.0001-beta
commit = True
tag = True
push = True

[pycalver:file_patterns]
setup.cfg =
    current_version = {version}
setup.py =
    version="{pep440_version}"
src/myproject.py =
    __version__ = "{version}"
README.md =
    [PyCalVer {calver}{build}-{release}]
    img.shields.io/badge/PyCalVer-{calver}{build}--{release}-blue
```

### Bump It Up

To increment and publish a new version, you can use the
`pycalver bump` command:

```shell
$ pycalver bump
```

This will do a few things

 0. Check that you don't have any non-committed local changes.
 1. Fetch the most recent global vcs tags from origin.
 2. Generate a new version, incremented from on the most recent
    tag on any branch.
 3. Update version strings in all configured files.
 4. Commit the updated version strings.
 5. Tag the new commit.
 6. Push the new commit to origin.

The current version is defined either as

 - The lexically largest git/mercurial tag in the repository.
 - The value of `pycalver.current_version` in setup.cfg

The git/mercurial tags are used to minimize the chance that the
same version will be generated for different revisions. As part
of doing `pycalver bump`, your local repository is updated
using `git fetch --tags`/`hg pull`, to ensure that all tags are
known locally
git push --follow-tags

the version To
avoid this completely you n
The value in setup.cfg is only used on projects that don't use
revision control.
If your project does not use git or mercurial for version
control, then the current_version will be set by `pycalver init`.


```shell
$ pycalver show
Current Version: v201809.0001-beta
PEP440 Version: 201809.1b0

$ pycalver bump --dry
TODO: diff output
Don't forget to do $ git push --tags
```

TODO: commits and tags


### Pattern Search and Replacement

`patterns` is used both to search for version strings and to
generate the replacement strings. The following placeholders are
available for use, everything else in a pattern is treated as
literal text.


|   placeholder    |      example       |
|------------------|--------------------|
| `pep440_version` | 201809.1b0         |
| `version`        | v201809.0001-alpha |
| `calver`         | v201809            |
| `year`           | 2018               |
| `month`          | 09                 |
| `build`          | .0001              |
| `release`        | -alpha             |


Note that the separator/prefix characters are part of what is
matched and generated for a given placeholder, and they should
not be included in your patterns.

A further restriction is, that a version string cannot span
multiple lines in your source file.

Now we can call `pycalver bump` to bump all occurrences of
version strings in these files. Normally this will change local
files, but the `--dry` flag will instead display a diff of the
changes that would be applied.


## Rational

### Other Versioning Software

This project is very similar to
[bumpversion](https://github.com/peritus/bumpversion), upon which
it is partially based. So why another library?
PyCalVer version strings can be
generated automatically, usage is a bit more simple.


### Some Details

 - Version numbers are for public releases. For the purposes of
   development of the project itself, reference VCS branches and
   commit ids are more appropriate.
 - There should be only one person or system responsible for
   updating the version number at the time of release, otherwise
   the same version number may be generated for different builds.
 - Lexical order is


Canonical PyCalVer version strings can be parsed with this
regular expression:


These are the full version strings, for public announcements and
conversations it will often be sufficient to refer simply to
`v201801`, by which the most recent `post` release build of
that month is meant.


```
version_str = "v201712.0027-beta"
version_dict = pycalver_re.match("v201712.0027-beta").groupdict()
import pkg_resources    # from setuptools
version = pkg_resources.parse_version(version_str)
--

In [2]: version_dict
{'year': '2017', 'month': '12', 'build_nr': '0027', 'tag': 'beta'}
>>> str(version)
201712.27b0
```



### Realities of Version Numbers

Nobody knows what the semantics of a version number are, because
nobody can guarantee that a given release adheres to whatever
convention one would like to imbibe it with. Lets just keep things
simple.

 - Version numbers should be recognizable as such, that's what
   the "v" prefix does.
 - A number like 201808 is recognizable to many as a number
   derived from a calendar.
 - alpha, beta are common parlance indicating software which is
   still under development.

Some additional constraints are applied to conform with PEP440


### Should I use PyCalVer for my Project?

If your project is 1. not useful by itself, but only when used
by other software, 2. has a finite scope/a definition of "done",
3. your project has CI, a test suite with and decent code
coverage, then PyCalVer is worth considering.
You release at most once per month.


### Marketing/Vanity

Quotes from http://sedimental.org/designing_a_version.html


### Rational

PyCalVer is opinionated software. This keeps things simple,
when the opinion match yours, but makes it useless for
everybody else.

The less semantics you put in your version string, the better.
The ideal would be to only have a single semantic: newer ==
better.

Some projects depend recursively on hundreds of libraries, so
compatibility issues generated by your project can be a heavy
burden on thousands of users; users who learn of the existence
of your library for the first time in the form of a stack-trace.
PyCalVer is for projects that are committed to and can maintain
backward compatibility. Newer versions are always better,
updates are always safe, an update won't break things, and if it
does, the maintainer's hair is on fire and they will publish a
new release containing a fix ASAP.

Ideally, your user can just declare your library as a
dependency, without any extra version qualifier, and never have
to think about it again. If you do break something by accident,
their remedy is not to change their code, but to temporarily pin
an earlier version, until your bugfix release is ready.

PyCalVer is for projects which are the mundane but dependable
foundations of other big shiny projects, which get to do their
big and exciting 2.0 major releases.


### Breaking Things is a Big Deal

Using an increment in a version string to express that a release
may break client code is not tenable. A developer cannot be
expected to think about how their code may or may not break as a
consequence of your decision to rename some functions. As the
author of any software, there is a great temptation to move fast
and break things. This is great when no other software depends
on yours. If something breaks, you jump up and fix it. The story
is quite different even when only a few dozen people depend on
your software.


The less the users of your library have to know about your
project, the better. The less they have to deal with issues
of compatibility, the better. SemVer can be overly specific
for some kinds of projects. If you are writing a library
and you have a commitment to backward compatibility

PyCalVer version strings can be parsed according to PEP440
https://www.python.org/dev/peps/pep-0440/


### A Word on Marketing

This setup of expectations for users can go one of two ways,

We use version numbers to communicate between the authors
of software and its users. For users of libraries Particularly
for libraries, it pays to keep things as simple as possible for
your human users.


### Commitment to Compatibility

Software projects can depend on many libraries. Consider that one
package introducing a breaking change is enough to mess up your
day. Especially in the case of libraries, your users should be
able to write code that uses it and not have that code break at
any point in the future. Users cannot be asked to keep track of
all the changes to every little library that they use.

PyCalVer is explicitly non semantic. A PyCalVer version number does
not express anything about

    - Don't ever break things. When users depend on your
      software, backward compatibility matters and the way to
      express backward incompatible changes is not to bump a
      version number, but to change the package name. A change
      in the package name clearly communicates that a user must
      change their code so that it will work with the changed
      API. Everybody who does not have the bandwidth for those
      changes, doesn't even have to be aware of your new
      release.

    - When you do break something, that should be considered a
      bug that has to be fixed as quickly as possible in a new
      version. It should always be safe for a user to update
      their dependencies. If something does break, users have to
      temporarily pin an older (known good) version, or update
      to a newer fixed version.

    - Version numbers should not require a parser (present
      package excluded of course). A newer version number should
      always be lexically greater than an older one.
      TODO:
      https://setuptools.readthedocs.io/en/latest/setuptools.html#specifying-your-project-s-version


The main component of the version number is based on the
calendar date. This is allows you to show your commitment (or
lack thereof) to the maintenance of your library. It also
allows users to see at a glance that their dependency might be
out of date. In this versioning scheme it is completely
reasonable to bump the version number without any changes,
simply to express to your users, that you are still actively
maintaining the software and that it is in a known good state.


For a much more detailed exposition of CalVer, see
http://sedimental.org/designing_a_version.html
https://calver.org/

from pkg_resources import parse_version


### The Life of a Library

```
mylib      v201711.001-alpha     # birth of a project (in alpha)
mylib      v201711.002-alpha     # new features (in alpha)
mylib      v201712.003-beta      # bugfix release (in beta)
mylib      v201712.004-rc        # release candidate
mylib      v201712.005           # stable release
mylib      v201712.006           # stable bugfix release

mylib2     v201712.007-beta      # breaking change (new package name!)
mylib2     v201801.008-beta      # new features (in beta)
mylib2     v201801.009           # stable release

mylib      v201802.007           # security fix for legacy version
mylib2     v201802.010           # security fix

mylib2     v202604.9900           # threshold for four digit build numbers
mylib2     v202604.9901           # still four digits in the same month
mylib2     v202604.9911           # last build number with four digits
mylib2     v202605.09912          # build number zero padding added with date turnover
mylib2     v202605.09913          # stable release

mylib2     v203202.16051-rc       # release candidate
mylib2     v203202.16052          # stable release

...
v202008.500    # 500 is the limit for four digit build numbers, but
v202008.508    # zero padding is added only after the turnover to
v202009.0509   # a new month, so that lexical ordering is preserved.
```


The date portion of the version, gives the user an indication of
how up their dependency is, whether or not a project is still
being maintained.

The build number, gives the user an idea of the maturity of the
project. A project which has been around long enough to produce
hundreds of builds, might be considered mature, or at least a
project that is only on build number 10, is probably still in
early development.


### FAQ

Q: "So you're trying to tell me I need to create a whole new
package every time I introduce a introduce a breaking change?!".

A: First of all, what the hell are you doing? Secondly, YES!
Let's assume your little package has even just 100 users. Do you
have any idea about the total effort that will be expended
because you decided it would be nice to change the name of a
function? It is completely reasonable introduce that the
friction for the package author when the price to users is
orders of magnitude larger.


1801

https://calver.org/

I have given up on the idea that version numbers express
anything about changes made between versions. Trying to
express such information assumes 1. that the author of a package
is aware of how a given change needs to be reflected in a
version number and 2. that users and packaging software correctly
parse that meaning. When I used semantic versioning, I realized that
the major version number of my packages would never change,
because I don't think breaking changes should ever be



[repo_ref]: https://gitlab.com/mbarkhau/pycalver

[build_img]: https://gitlab.com/mbarkhau/pycalver/badges/master/pipeline.svg
[build_ref]: https://gitlab.com/mbarkhau/pycalver/pipelines

[codecov_img]: https://gitlab.com/mbarkhau/pycalver/badges/master/coverage.svg
[codecov_ref]: https://mbarkhau.gitlab.io/pycalver/cov

[license_img]: https://img.shields.io/badge/License-MIT-blue.svg
[license_ref]: https://gitlab.com/mbarkhau/pycalver/blob/master/LICENSE

[mypy_img]: https://img.shields.io/badge/mypy-checked-green.svg
[mypy_ref]: http://mypy-lang.org/

[style_img]: https://img.shields.io/badge/code%20style-%20sjfmt-f71.svg
[style_ref]: https://gitlab.com/mbarkhau/straitjacket/

[downloads_img]: https://pepy.tech/badge/pycalver
[downloads_ref]: https://pepy.tech/project/pycalver

[version_img]: https://img.shields.io/badge/PyCalVer-v201809.0002--beta-blue.svg
[version_ref]: https://pypi.org/project/pycalver/

[pypi_img]: https://img.shields.io/badge/PyPI-wheels-green.svg
[pypi_ref]: https://pypi.org/project/pycalver/#files

[pyversions_img]: https://img.shields.io/pypi/pyversions/pycalver.svg
[pyversions_ref]: https://pypi.python.org/pypi/pycalver