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Naveen Naidu

GSOC - Phase 1 Overview

gsoc4 min read

Hiya crawlers!

This post will cover my learnings of phase 1 of GSoC with coala. As I explained in my previous GSOC post about the 4 different phases of my project. For the uninitatied, the project for my GSoC is to add functionality into coala which would enable it into Linting files that have nested languages.

I divided my project into 4 phases:

  • Information Gathering
  • Segregating the nested file
  • Linting the file
  • Assembling

For the newbies here, I highly suggest that you read the previous blog about the project. If you do feel lazy(when don't we :P) to go through the 700+ lines of content, I better give you a very high level view of the project:

A higher level view of the implementation

A source file containing multiple programming languages is loaded up by coala. The original nested file is broken/split into n temporary files, where n is the number of languages present in the original file. Each temporary file only contains the snippets belonging to one language.

These temporary files would then be passed to their respective language bears ( chosen by the user) where the static analysis routines would run. The temporary files after being linted would then be assembled. The above process creates the illusion that the original file is being linted, but in reality we divide the files into different parts and lint them one by one.

The figure below, would help give a clear picture


If it's hard for you imagine - Think of it something like this, You are a factory worker working in a ball manufacturing company. This company produces two kind of balls - One red and one blue. Both these balls have differnt properties and shapes. This factory is equipped with a Big Ball Production Unit, but alas - This unit produces both red and blue balls at the same time.As a result of which after one production cycle the output box/carton has mixture of Red and Blue balls.

Your taks as a factory worker is to segregate the red and blue balls into different boxes and take these to the Ball Testers. Since the balls have different properties, you cannot take it to the same testers, hence you will take the Blue Ball to the Blue Ball Validator and Red Ball to the Red Ball Validator.

These Validator validates the quality of the ball and discard the bad quality balls and replaces them with a nice quality balls.

Once the Validation is done, You now have two boxes - One for Red balls with no defects and one for Blue Balls with no defects. Your final job is to combine both these boxes. (Factory worker thinks: Duh! Why did you make me segregate the ball in the first place -.-)

The above analogy is what my work is all about. The factory worker is the coala tool. The ball tester are the coala bears/linters. The carton/box is the nested file that had mixture of languages(read balls). The nested file(the box with the mixture of two different color balls) is seperated into two different section where each section contains the lines of only one language(read, the red and blue ball from the box is segeragated into red box and Blue Box).

These sections that contain purely only one language(boxes with only one single color ball) is then taken to the respective coala-bears(read Ball validators), these coala bears validates the files and fixes the file if any change needs to be done (Note: coala-bears are linters) and then send theses validated/linted file back to coala(the two box with proper quality balls are handed back to factory worker). coala then finally mereges back both the files (read: Factory worker then puts both the validated balls back into the same box)

Phase 1 Work

In Phase 1 of GSoC I decided to first handle the task of segregating the nested file into different sections. My aim in this phase was to be able to identify the sections that belongs to a particular language.

Let's understand what this means:

Suppose we have the following nested file which has both Jinja and Python.

1import sys
2import thanos
4x = "hulk"
6{% raw %}{% if x == "hulk" %}
7 print("Thanos is meat")
8{% else %}
9 print("Bhubyee! Earth")
10{% endif %}{% endraw %}
12if(y is not x):
13 "Some gibberish"

As you see in the above snippet - We have a mixture of Python and Jinja. And if we have to be able to lint these files seprately i.e if we have to convert the above file into pure jinja and pure python file, we would need to maintain the information about what lines belong to which language.

We do this, by divinding the files into different section. I call these section NlSection which stand for Nested language Section.

The above snippet can be divided into three sections:

  1. Section 1
1import sys
2import thanos
4x = hulk
  1. Section 2 {% raw %}
1{% if x == "hulk" %}
2 print("Thanos is meat")
3{% else %}
4 print("Bhubyee! Earth")
5{% endif %}

{% endraw %}

  1. Section 3
1if(y is not x):
2 print("Some gibberish")

Divinding the files into various sections, makes the work of linting the file easier. What we do after creating sections is that we group the sections on the basis of their language and then make pure python and a pure jinja file. These pure files would then be passed upon to the respective language bears.

NOTE: Creating sections does mean that we create new sections rather I mean that we maintain the infromation such as the line_start and line_end in the original file.


Each of the section we made in the nested language file is termed as NlSection. A NlSection has the following information:

  • Start line number of the section
  • Start column number of the section
  • End line number of the section
  • End column number of the section
  • The path of the nestedfile

The start and end information of the sections are inturn a NlSectionPosition object.

That means NlSection comprises of two object start and end, and these objects are of the type NlSectionPosition.

NlSectionPosition has better functionality to store line numbers and column numbers along with proper testing.


Parsers are responsible to take in the input nested file and split out the NlSections list. For my case - I have as of now only made a parser that can for the combination of Jinja and Python. I named it as PyJinjaParser.

This parser can take in a nested Jinja and Python file and emit out the list of NlSections of Python and Jinja.

The above explanation sums up pretty much my work for Phase 1. I wish to write about this in more details - but time bounds me :/

The Link to Phase 1 PR

For now, I would refer you to the above PR link, I have seen to that it is well documented. Thanks to my mentor Virresh - I did write enough tests to give me peace of mind that the work until now works.


I have passed Phase 1. Hurrah!. I must thank my mentor for his valuable feedback and his patient reviews. Honestly I myself was skeptical of making it this far. You know, handling OMP, Exams and GSOC. But everything did work out fine. My final exam would be on 3rd of July. It's python - So it's pretty chill.

So unofficially - My exams have already ended today :P

Also, the community bonding of Open mainframe is done too. Stipend of both GSoC and OMP have been released. It kinda feel good. My Second salary :)

Ahaaahhh! I gotta go now - How I wish I can write more. Alas! that's it for now my dear bots. Saynora until next post :)