coala Tutorial¶
Welcome to this little tutorial. It is meant to be a gentle introduction to the usage of coala.
Prerequisites¶
In order to complete this tutorial you will need coala installed. (Installation is actually not required but it’s more convenient and recommended.)
Get Some Code¶
In order to perform a static code analysis on your code you will need some code to check. If you do not have own code you want to check, you can retrieve our tutorial samples:
git clone https://github.com/coala-analyzer/coala-tutorial.git
Please note that the commands given in this tutorial are intended for use with this sample code and may need minor adjustments.
Let’s Start!¶
There are two options how to let coala know what kind of analysis it should perform on which code.
Command Line Interface¶
In order to specify the files to analyze, you can use the --files
argument of coala like demonstrated below. For all file paths, you can
specify (recursive) globs.
Because analysis routines can do many various things we named them
Bears. Thus you can specify the kind of analysis with the --bears
argument.
Please type the following commands into the console:
cd coala-tutorial
coala --files=src/\*.c --bears=SpaceConsistencyBear --save
coala will now ask you for missing values that are needed to perform the
analysis, which in this case is only the use_spaces
setting. We
recommend setting it to true
.
coala will now check the code and, in case you use the tutorial code, yield two results. In the case of the SpaceConsistencyBear you will see trailing whitespace errors on your console.
Feel free to experiment a bit. You’ve successfully analysed some code! But don’t stop reading - you don’t have to enter all those values again!
Configuration Files¶
coala supports a very simple configuration file. If you’ve executed the instructions from the CLI section above, coala will already have such a file readily prepared for you. Go, take a look at it:
cat .coafile
This should yield something like this:
[Default]
bears = SpaceConsistencyBear
files = src/*.c
use_spaces = yeah
If you now invoke coala
it will parse this .coafile
from your
current directory. This makes it easy to specify once for your project
what is checked with which bears and make it available to all
contributors.
Feel free to play around with this file. You can either edit it manually
or add/edit settings via coala --save ...
invocations. If you want
coala to save settings every time, you can add save = True
manually
into your .coafile
.
Sections¶
Thats all nice and well but we also have a Makefile for our project we want to check. So let us introduce another feature of our configuration syntax: sections.
The line [Default]
specifies that everything below will belong to
the Default section. If nothing is specified, a setting will implicitly
belong to this section.
Let’s check the line lengths of our Makefile:
coala -S Makefiles.bears=LineLengthBear Makefiles.files=Makefile --save
As you can see, the -S
(or --settings
) option allows to specify
arbitrary settings. Settings can be directly stored into a section with
the section.setting
syntax.
By default the LineLengthBear
checks whether each line contains
80
chars or less in a line. To change this value, use the
max_line_length
inside the .coafile
.
coala will now yield any result you didn’t correct last time plus a new
one for the Makefile. This time coala (or better, the
LineLengthBear
) doesn’t know how to fix the issue but still tries to
provide as much helpful information as possible and provides you the
option to directly open the file in an editor of your choice.
Note
If your editor is already open this may not work, because the other process will shortly communicate with the existent process and return immediately. coala handles this for some editors automatically, if your’s does not work yet - please file a bug so we can include it!
If you changed one file in multiple results, coala will merge the changes if this is possible.
coala should have appended something like this to your .coafile
:
[Makefiles]
bears = LineLengthBear
files = Makefile
As you see, sections provide a way to have different configurations for possibly different languages in one file. They are executed sequentially.
Auto-applying results¶
Often you don’t want to look at trivial results like spacing issues. For
that purpose coala includes a special setting called default_actions
that allows you to set the action for a bear that shall be automatically
applied on run.
Let’s automatically fix python code. Take a look at our sample python code:
$ cat src/add.py
"""
This is a simple library that provide a function that can add numbers.
Cheers!
"""
def add(a,b):
return a+b;
import sys
That looks horrible, doesn’t it? Let’s fix it!
$ coala -S python.bears=PEP8Bear python.files=\*\*/\*.py \
python.default_actions=PEP8Bear:ApplyPatchAction --save
# other output ...
Executing section python...
[INFO][11:03:37] Applied 'ApplyPatchAction' for 'PEP8Bear'.
[INFO][11:03:37] Applied 'ApplyPatchAction' for 'PEP8Bear'.
coala would now fix all spacing issues and without bothering you again.
Currently following actions are available:
ApplyPatchAction
: Applies a given patch (if existent).ShowPatchAction
: Just displays a given patch (if existent) without doing something.
For debugging purposes:
PrintDebugMessageAction
: Prints a debug message for the appearing result.
Setting Inheritance¶
All settings in the default section are implicitly inherited to all other sections (if they do not override their values). We can use that to save a few lines!
Lets add the following section to our .coafile
:
[TODOS]
bears = KeywordBear
And execute coala with the -s
argument which is the same as
--save
. I recommend setting case insensitive keywords to
TODO, FIXME
and case sensitive keywords empty.
After the results we’ve already seen, we’ll see a new informational one which informs us that we have a TODO in our code.
Did you note that we didn’t specify which files to check this time? This
is because all settings, including files = src/*.c
, from the Default
section are already available in every other section implicitly. Thus
the default section is a good point to set things like logging and
output settings or specifying a default set of files to check.
Ignoring Issues¶
There are several ways to ignore certain issues, so you aren’t lost if any routines yield false positives.
Ignoring Files¶
coala lets you ignore whole files through the ignore
setting:
files = **/*.h
ignore = **/resources.h
This configuration would include all header (.h
) files but leaves
out resource headers.
Ignoring code Inside Files¶
Sometimes you need finer-graded ignores. Imagine you have a
LineLengthBear
that shall not run on some code segments, because you
can’t wrap them:
code = "that's checked normally"
# Ignore LineLengthBear
unwrappable_string = "some string that is long and would exceed the limit"
You can also skip an area:
# Start ignoring LineLengthBear
unwrappable_string_2 = unwrappable_string + "yeah it goes even further..."
another_unwrappable_string = unwrappable_string + unwrappable_string_2
# Stop ignoring
You can also conditionally combine ignore rules! Bear names will be
split by comma and spaces, invalid bear names like and
will be
ignored.
Also note that in the bear names delimited by commas and spaces, you may specify glob wildcards that match several bears:
# Start ignoring Line*, Py*
unwrappable_string_2 = unwrappable_string + "yeah it goes even further..."
another_unwrappable_string = unwrappable_string + unwrappable_string_2
# Stop ignoring
In the above example all bears matching the glob Line* and Py* will be ignored. You may also specify more complex globs here such as # Start ignoring (Line*|P[yx]*) which will ignore all bears start with Line, Py, and Px.
# Ignore LineLengthBear and SpaceConsistencyBear
variable = "Why the heck are spaces used instead of tabs..." + "so_long"
If you put an all
instead of the bear names directly after the
ignore
/ignoring
keyword, the results of all bears affecting
those lines will be ignored.
Enabling/Disabling Sections¶
Now that we have sections we need some way to control, which sections are executed. coala provides two ways to do that:
Manual Enabling/Disabling¶
If you add the line TODOS.enabled=False
to some arbitrary place to
your .coafile
or just enabled=False
into the TODOS
section,
coala will not show the TODOs on every run.
Especially for those bears yielding informational messages which you might want to see from time to time this is a good way to silence them.
Specifying Targets¶
If you provide positional arguments, like coala Makefiles
, coala
will execute exclusively those sections that are specified. This will
not get stored in your .coafile
and will take precedence over all
enabled settings. You can specify several targets seperated by a space.
What was that TODO again?
Show bears’ information¶
To get help on using a bear or to get a description of the bear, use the
--show-bears
argument:
coala --bears=SpaceConsistencyBear --show-bears
This will display a large amount of information regarding the bears that
have been specified (in the .coafile
of in the CLI arguments). It
shows:
- A description of what the bear does
- The sections which uses it
- The settings it uses (optional and required)
Integrating coala into Your Project¶
It’s easy to add coala to your project in a way that does not force your developers even to install coala using git submodules. This also has the advantage that all your developers are using exactly the same version of coala. You can try it out in the coala-tutorial repository:
git submodule add https://github.com/coala-analyzer/coala.git
git commit -m 'Add coala submodule'
git add .coafile
git commit -m 'Add .coafile'
You can now use coala/coala
as if it were the installed binary.
Here’s the instructions for your developers:
git submodule init
git submodule update
coala/coala
Continuing the Journey¶
If you want to know about more options, take a look at our help with
coala -h
. If you liked or disliked this tutorial, feel free to drop
us a note at our bug tracker (github) or mailing list
(https://groups.google.com/forum/#!forum/coala-devel).
If you need more flexibility, know that coala is extensible in many ways due to its modular design:
- If you want to write your own bears, take a look at sources lying in
bears
andcoalib/bearlib
. - If you want to add custom actions for results, take a look at the
code in
coalib/results/results_actions
. - If you want to have some custom outputs (e.g. HTML pages, a GUI or
voice interaction) take a look at modules lying in
coalib/output
.
Happy coding!