Lesson 15: Dev Processes & Tools

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Overview

Code Analysis

Code analysis tools are some of the most important tools in a developer's arsenal when it comes to finding and fixing bugs. Code analysis tools come in two flavors:

Static Analysis:
A tool performs static analysis if it works without running your code. Examples include linters and type checks.
Dynamic Analysis:
Dynamic Code Analysis tools actually run your code and verify it by watching how the program acts. Examples include rspec for Ruby.

Debugging Tools

Debuggers are interactive dynamic analysis tools that are used to inspect your code as it runs.

CLI Debugging Tools

C/C++ Tools

Python Tools

NodeJS Tools

Web Consoles

Firefox Console

Linters

Linters inspect your code and flags suspicious usage. This can be to enforce a style guide or to flag code which will probably not compile or break the program when it is running.

Examples:
  • flake8 (Python)
  • rubocop (Ruby)
  • splint (C)
  • jshint (NodeJS)
src/times.js: line 407, col 20, Expected '{' and instead saw 'return'.
src/times.js: line 415, col 49, Missing semicolon.
src/times.js: line 407, col 58, 'error' is not defined.

Code Coverage

Code Coverage is the process of running your tests and keeping track of which lines, logic branches, and files are used in the test suite.

This is useful because it demonstrates how much your tests are actually doing (proving your program does what it should) and proves if you're carrying around a bunch of dead code.

Name                      Stmts   Miss  Cover   Missing
-------------------------------------------------------
my_program.py                20      4    80%   33-35, 39
my_other_module.py           56      6    89%   17-23
-------------------------------------------------------
TOTAL                        76     10    87%

Integrated Development Environments (IDE)

Debugging in Minecraft

IDEs are programs used to help developers get their job done by integrating many essential tools into one ecosystem.

Integrated Development Environments (IDE)

Examples:
  • Netbeans (Java)
  • Visual Studio (.NET)
  • PyCharm (Python)
  • Eclipse (Many)
  • Atom (Many)

Style Guides

XKCD Code Quality comic

Style Guides are rules for formatting your code in a consistent way. This is to avoid differences in aesthetic as well as functional style of a program.

Style Guides, when enforced correctly, make the code-base of a project more readable and understandable.

Example: Real-World Style Guides

The Linux kernel style guidelines are actually fun to read:

"First off, I’d suggest printing out a copy of the GNU coding standards, and NOT read it. Burn them, it’s a great symbolic gesture."

—Linux Kernel Coding Style

NASA’s Jet Propulsion Laboratory style guidelines are very short and are concerned with automated tooling to do code analysis:

"All loops shall have a statically determinable upper-bound on the maximum number of loop iterations."

—JPL Coding Standard

Dependency Isolation

Dependency isolation is the process of -- wait for it -- isolating the dependencies of a project. This is a surprisingly hard problem and many consider it largely unsolved.

TODO: Python Virtualenvs

Setup and enter the virtual environment.

$ virtualenv <virtualenv name>
New python executable in /path/to/<venv name>/bin/python
Installing setuptools, pip, wheel...
done.
$ source <venv name>/bin/activate

Install a package. This installs it in the current working directory and so does not ask for root permissions.

(<venv name>) $ pip install flask
[...]

TODO: Python Virtualenvs

To list all packages in the venv:

(<venv name>) $ pip freeze
click==6.7
Flask==1.0.2
itsdangerous==0.24
Jinja2==2.10
MarkupSafe==1.0
Werkzeug==0.14.1

Deactivate (leave) the venv.

(<venv name>) $ deactivate
$

Other Examples

Node.js:
Creates a node_modules directory and tracks dependencies in package.json.
Go:
Dependencies are tracked via git repositories and using the go get command.
Rust:
Dependencies and versions are specified in Cargo.toml. All compiled code (and dependencies) are stored in a target directory.

Development Servers

A Carbon Copy of the Production Environment(s)

Development servers are used to test that your code works in a real environment, with a real server, and real data. You shouldn't throw your code up on a production website to see if it works, so a development server is as close to the real thing as you can get.

Further Reading