Versioning

class: center, middle

# We are still bad at versioning

a ☇ talk

pygraz, meisterluk, 2018/03/06

---

# Hey, I want to implement X. How?

Use python!

```
user@shell ~ % python
Python 3.5.2 (default, Nov 23 2017, 16:37:01) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> print "Hello World"
  File "<stdin>", line 1
    print "Hello World"
                      ^
SyntaxError: Missing parentheses in call to 'print'
>>> 
```

We (people in IT) are not beginners-friendly.

---

# What is the problem?

Version management.

---

# Fact: Py3k was backwards-incompatible

Why?

- long versus int
- unicode mess
- relative imports
- int vs float division
- nonlocal variables
- ...

via Guido's PyCascades slides (Jan 2018)

> Not all warts could be fixed without breaking compatibility
>
> esp. the unicode mess

---

# Question: Is this okay?

Should software change? If it changes, what changes?

- TeX: frozen and converging towards 𝛑
- pretty much every other software: new features, refactoring, improvements, security patches.

I personally advocate, that software _changes_ over time.
If there is a need for this software, it will improve and **refactoring** and **patching** is an essential part of the development.

---

# Claim: Version numbers are good

If software changes, the version number changes.

Example `requirements.txt`:

```
et-xmlfile==1.0.1
jdcal==1.3
openpyxl==2.4.9
pytest==3.2.3
ruamel.yaml<=0.15
```

Yay, version numbers!
Wait... does it require python 2.7 or python 3.5?

Maybe setup.py will tell you:

```
  classifiers=['Programming Language :: Python :: 3']
```

---

# My point today

- if the software behavior changes, the identifier changes
    * TeX uses name as identifier
        - everything okay!
        - but TeX did not evolve and few forks
        - maybe not a good example

* identifier for every other software:
        1. name
        2. version number

---

# Fact: Semantic Versioning exists

Release 1.5.2

- MAJOR version when you make incompatible API changes
- MINOR version when you add functionality in a backwards-compatible manner
- PATCH version when you make backwards-compatible bug fixes

MAJOR=1 MINOR=5 PATCH=2

Non-chronological.

https://semver.org/

---

# Best approach?

Rolling releases? Timestamp as version number?

Desired as developer:

- dependencies never change (even for security fixes, they might break something)
- publish it to a centralised host
- it is easy to publish a new version

Desired as sysadmin:

- all software is kept up2date
- retrieval from decentralised/many hosts
- it is easy to deploy an arbitrary version

For both:
- Easy migration from creator to creator, distributor to distributor, hoster to hoster

In general:
We need reproducible builds. We need origin integrity. Both are widely adopted today. Thanks!

Semantic versioning does not all problems. But it helps.

---

# Fact: go is starting to advocate Semantic Versioning

Rationale by Russ Cox: https://research.swtch.com/vgo

Introducing a `mod.go` file:

```
module "github.com/you/hello"

require "rsc.io/quote" v1.5.2
```

---

# Fact: we ignore versioning

Python was designed in 1991. `requirements.txt` was invented much later. Semantic versioning appeared much later.

Go was designed in **2009**. Go could have done better from the beginning. No lessons learned.

---

# Issue 1: On UNIX commands are called by name, not (name, version)

We still say `python`. Is it `python3` oder `python`?

```
#!/usr/bin/env python
```

```
#!/usr/bin/env python3
```

Specify!

---

# Issue 2: ALWAYS think about the version

Do I import the correct version of the library?
Did I pick the correct version number for this release?

Provide executables with version numbers in the name.
Embed a version number when designing a network protocol.
Or simply, in any protocol.

---

# Will we become beginners-friendly?

~~I learned to program in python~~.

I learned to program in python 3.

At least, the previous issue won't happen again.

---

# Homework

- Guido van Rossum: [BDFL Python 3 retrospective](https://www.youtube.com/watch?v=Oiw23yfqQy8)
- Read [semver.org](https://semver.org/)
- Advocate 'think of the version number'

---

# Cheers

Thank you!

<p style="margin-top:100px; font-size:small">Slides version 1.0.2</p>