Comparing Semantic Versions

This repository contains a fully tested and easily extendable function to compare semantic versions. See the corresponding presentation for more details on the function as well as semantic versioning.

Implemented Functionality

A semantic versioning comparator compare(version_1, version_2) is implemented which

accepts two version strings, referred to as version_1 and version_2
every version string may only contain integer numbers and dots
every version string must start with an integer
version_1 must also contain a leading comparator out of a list of known comparators
known comparators are =, >, and >=
return values are only True or False

Assumptions

The following assumptions were made:

version_1 is the only version string which contains a comparator
The question answered by compare(version_1, version_2) is "version_2 version_1"; i.e. compare('>=1.0', '1.1') answers the question of '1.1''>=1.0'
versions cannot be empty
Version numbers are compared from left to right, split at "."

Implementation Notes

The compare(version_1, version_2) was implemented in standard Python 2.7 by

Splitting the comparator from version_1 and passing it on the corresponding comparator class
Parsing version_1 and version_2 into lists of integers, splitting them at the "." symbol
Handing the two parsed versions to the previously detected comparator and return the result

Should any of the above steps fail, a detailed error message is being displayed.

Known Limitations and Assumptions

As the implementation relies on list comparison, all limitations of standard Python 2.7.13 list comparision apply.

Extensions

The task was implemented with extendability in mind. Adding a new comparator is fairly straightforward. All that needs to be done is use of the existing comparators as a template and provide the comparator specific

SYMBOL as well as
compare method.

The comparator is then made available by adding it to the KNOWN_SYMBOLS_TO_COMPARATORS_MAPPING in the VersionComparator class. Should the power of the Version class be leveraged, then the corresponding magic method in the Version class has to be provided.

Testing

As the compare(version_1, version_2) function does not provide any main functionality, the tests (and associated logging output) provide some insight.

Run the tests from the base directory of this project via

python -m unittest discover tests/

Note: Base Class tests are skipped on purpose as the tests require a comparator to be meaningful.

Just as the actual application is written with extendability in mind, so are the tests. Adding a new comparator is again fairly straightforward. All that needs to be done is use of the existing comparator test cases as a template and provide the comparator specific private methods. All other functional tests are included in the base version test as they are common across all comparators.

Using the Comparator

The function compare(version_1, version_2) can be used directly after importing as outlined in the minimum example

from main import compare

print compare('>3.14.159', '3.14.159.2653')

When run via

python minimum_example.py

the following output is printed

2017-09-17 19:21:06,057 - root - INFO - Found comparator ">" and version "3.14.159" in string ">3.14.159"
2017-09-17 19:21:06,058 - root - INFO - Found matching class "<class 'comparators.strictly_greater.StrictlyGreater'>" for string ">"
2017-09-17 19:21:06,058 - root - INFO - Comparing Versions:  3.14.159.2653 > 3.14.159 : True
True

Here, the last True corresponds to the expected output of the compare('>3.14.159', '3.14.159.2653') function as also indicated by the preceding info log message.

Settings

The application does come with a settings.py module which mainly provides logging setup. It expects to be able to create a directory .logs (if not already present) and writes its logs to that directory as well.

dumrauf/semantic_versioning