Mozilla Web App Validator
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requirements.txt Validator

The Apps Validator is a tool designed to scan open web apps for problems and invalid code. By using a combination of various techniques and detection mechanisms, the validator is capable of being both efficient as well as thorough.

Build Status


Clone the repository

git clone git://

(or your own fork if you want to contribute to the project).

System Prerequisites

To run the validator, you'll need some basic software installed beforehand.

  • If you're using Ubuntu, you'll first need to install the python-dev package using aptitude or apt-get.
  • You'll need openssl. You can install this with brew on OS X or your favorite Linux package manager.

If you're on Ubuntu, you'll also need M2Crypto installed, which you can get by running

pip install git+git://


You can install everything you need for running and testing by changing to the directory where you cloned the code, and running

pip install -r requirements.txt

It's recommended that you install the requirements in a virtualenv rather than globally.


To run the full test suite, a copy of Spidermonkey is needed. To install on OS X, you should use Homebrew on OS X:

brew install spidermonkey

The default options in Homebrew will work with the validator.


If you pass the --acorn command line flag, the validator will use Acorn instead of Spidermonkey to parse JavaScript. This requires node.js and Acorn to be installed. Once you've installed node.js in your system, you can install Acorn with the following:

npm install acorn

Acorn will also be used if no Spidermonkey installation is found, though some features of JavaScript will be unavailable (particularly around ES6), and some unit tests will be skipped.

Acorn is used to run the test suite on Travis CI.


Run the validator as follows:

python app-validator <path to app> [-o <output type>] [-v] [--boring] [--unlisted]

The path to the app should point to a packaged app (.zip file) or a hosted app manifest URL.

The type of output to generate. Types are listed below.
Enable verbose mode. Extra information will be displayed in verbose mode, namely notices (informational messages), extra error info (like contexts, file data, etc.), and error descriptions. This only applies to ``-o text``.
Disables messages that are specific to apps hosted on Marketplace.
Disables colorful shell output.


The output type may be either of the following:

text (default)
Outputs a textual summary of the addo-on analysis. Supports verbose mode.
Outputs a JSON snippet representing a full summary of the analysis.

Text Output Mode

In text output mode, output is structured in the format of one message per line. The messages are prefixed by their priority level (i.e.: "Warning: This is the message").

At the head of the text output is a block describing what the app type was determined to be.

JSON Output Mode

In JSON output mode, output is formatted as a JSON snippet containing all messages. The format for the JSON output is that of the sample document below.

    "detected_type": "packaged_app",
    "errors": 2,
    "warnings": 1,
    "notices": 1,
    "success": false,
    "ending_tier": 4,
    "messages": [
            "uid": "123456789",
            "id": ["module", "function", "error"],
            "type": "error",
            "message": "This is the error message text.",
            "description": ["Description of the error message.",
                            "Additional description text"],
            "file": "chrome/",
            "line": 12,
            "column": 50,
            "context": [
                "   if(foo = bar())",
                "       an_error_is_somewhere_on_this_line.prototy.eval('whatever');",
            "tier": 2

A copy of the app's manifest (packaged or hosted) will be included in the manifest field of the output.

Line Numbers and Columns

Line numbers are 1-based. Column numbers are 0-based. This can be confusing from a programmatic standpoint. "Line one" would refer to the first line of a file.


The context attribute of messages will either be a list or null. Null contexts represent the validator's inability to determine surrounding code. As a list, there will always be three elements. Each element represents a line surrounding the message's location.

The middle element of the context list represents the line of interest. If an element of the context list is null, that line does not exist. For instance, if an error is on the first line of a file, the context might look like:

    "This is the line with the error",
    "This is the second line of the file"

The same rule applies for the end of a file and for files with only one line.


Unit tests can be run with



Some regular maintenance needs to be performed on the validator in order to make sure that the results are accurate.

JS Libraries

A list of JS library hashes is kept to allow for whitelisting. This must be regenerated with each new library version. To update:

cd extras
mkdir jslibs
python jslibs/
mv whitelist_hashes.txt ../appvalidator/testcases/hashes.txt

To add new libraries to the mix, edit extras/ and add the version number to the appropriate tuple.


If you find any bug, please file them on Bugzilla under Marketplace::Validation.


I've installed all the dependencies but Python still can't find some modules.

  • It's possible that you're running two versions of Python locally. If you run which python and which pip, the two files should be in the same location. If they're not, you'll need to remove one of the Python versions.
  • You might not have the appropriate virtualenv set up. Make sure to run the workon command or source /path/to/venv/bin/activate if you don't use virtualenvwrapper.

I'm getting errors about my package missing a manifest.

  • You might have used your operating system's Archive functionality. This sometimes adds an extra directory inside your ZIP file. E.g.: instead of your path reading /manifest.webapp, it looks like /my_app/manifest.webapp.