Coding Standards — pgAdmin 4 2.0 documentation

# Coding Standards

pgAdmin uses multiple technologies and multiple languages, each of which have their own coding standards.

## General

In all languages, indentations should be made with 4 spaces, and excessively long lines wrapped where appropriate to ensure they can be read on smaller displays (80 characters is used in many places, but this is not a required maximum size as it’s quite wasteful on modern displays). Typically lines should not be longer than 120 characters.

Comments should be included in all code where required to explain its purpose or how it works if not obvious from a quick review of the code itself.

## CSS 3

CSS3 is used for styling and layout throughout the application. Extensive use is made of the Bootstrap Framework to aid in that process, however additional styles must still be created from time to time.

Most custom styling comes from individual modules which may advertise static stylesheets to be included in the module that is loading them via hooks.

Styling overrides (for example, to alter the Bootstrap look and feel) will typically be found in the overrides.css file in the main static file directory for the application.

Styling should never be applied inline in HTML, always through an external stylesheet, which should contain comments as appropriate to explain the usage or purpose for the style.

Styles should be specified clearly, one per line. For example:

    /* iFrames should have no border */
    iframe {
        border-width: 0;
    }

    /* Ensure the codemirror editor displays full height gutters when resized */
    .CodeMirror, .CodeMirror-gutters {
        height: 100% !important;
    }

All stylesheets must be CSS3 compliant.

## HTML 5

HTML 5 is used for page structure throughout the application, in most cases being rendered from templates by the Jinja2 template engine in Flask.

All HTML must be HTML 5 compliant.

## Javascript

Client-side code is written in Javascript using jQuery and various plugins. Whilst much of the code is rendered from static files, there is also code that is rendered from templates using Jinja2 (often to inject the users settings) or constructed on the fly from module hooks.

A typical Javascript function might be formatted like this (this snipped is from a template):

    // Delete a server group
    function delete_server_group(item) {
        alertify.confirm(
            'Delete server group?',
            'Are you sure you wish to delete the server group "{0}"?'.replace('{0}', tree.getLabel(item)),
            function() {
                var id = tree.getId(item)
                $.post("{{ url_for('NODE-server-group.delete') }}", { id: id })
                    .done(function(data) {
                        if (data.success == 0) {
                            report_error(data.errormsg, data.info);
                        } else {
                            var next = tree.next(item);
                            var prev = tree.prev(item);
                            tree.remove(item);
                            if (next.length) {
                                tree.select(next);
                            } else if (prev.length) {
                                tree.select(prev);
                            }
                        }
                    }
                )
            },
            null
        )
    }

Note the use of a descriptive function name, using the underscore character to separate words in all lower case, and short but descriptive lower case variable names.

### C++

C++ code is used in the desktop runtime for the application, primarily with the QT framework and an embedded Python interpreter. Note the use of hanging braces, which may be omitted if on a single statement is present:

    // Ping the application server to see if it's alive
    bool PingServer(QUrl url)
    {
        QNetworkAccessManager manager;
        QEventLoop loop;
        QNetworkReply *reply;
        QVariant redirectUrl;

        url.setPath("/utils/ping");

        do
        {
            reply = manager.get(QNetworkRequest(url));

            QObject::connect(reply, SIGNAL(finished()), &loop, SLOT(quit()));
            loop.exec();

            redirectUrl = reply->attribute(QNetworkRequest::RedirectionTargetAttribute);
            url = redirectUrl.toUrl();

            if (!redirectUrl.isNull())
                delete reply;

        } while (!redirectUrl.isNull());

        if (reply->error() != QNetworkReply::NoError)
            return false;

        QString response = reply->readAll();

        if (response != "PING")
        {
            qDebug() << "Failed to connect, server response: " << response;
            return false;
        }

        return true;
    }

## Python

Python is used for the backend web server. All code must be compatible with Python 2.7 and should include PyDoc comments whilst following the official Python coding standards defined in PEP 8. An example function along with the required file header is shown below:

    ##########################################################################
    #
    # pgAdmin 4 - PostgreSQL Tools
    #
    # Copyright (C) 2013 - 2017, The pgAdmin Development Team
    # This software is released under the PostgreSQL Licence
    #
    ##########################################################################

    """Integration hooks for server groups."""

    from flask import render_template, url_for
    from flask.ext.security import current_user

    from pgadmin.settings.settings_model import db, ServerGroup

    def get_nodes():
        """Return a JSON document listing the server groups for the user"""
        groups = ServerGroup.query.filter_by(user_id=current_user.id)

        value = ''
        for group in groups:
            value += '{"id":%d,"label":"%s","icon":"icon-server-group","inode":true},' \
                     % (group.id, group.name)

        value = value[:-1]

        return value