Framework Overview


The Flectra Javascript framework is a set of features/building blocks provided by the web/ addon to help build flectra applications running in the browser. At the same time, the Flectra Javascript framework is a single page application, usually known as the web client (available at the url /web).

The web client started as an application made with a custom class and widget system, but it is now transitioning to using native javascript classes instead, and Owl as a component system. This explains why both systems are currently in use in the codebase.

From a high-level perspective, the web client is a single-page application: it does not need to request a full page from the server each time the user performs an action. Instead, it only requests what it needs and then replaces/updates the current screen accordingly. Also, it manages the url to keep it in sync with the current state.

The javascript framework (all or some parts) is also used in other situations, such as the Flectra website or the point of sale. This reference is mostly focused on the web client.


It is common in the Flectra ecosystem to see the words frontend and backend as synonyms for the flectra website (public) and the web client, respectively. This terminology is not to be confused with the more common use of browser-code (frontend) and server (backend).


In this documentation, the word component always refers to new Owl components, and widget refers to old Flectra widgets.


All new development should be done in Owl, if possible!

Code structure

The web/static/src folder contains all the web/ javascript (and css and templates) codebase. Here is a list of the most important folders:

  • core/ most of the low level features

  • fields/ all field components

  • views/ all javascript views components (form, list, …)

  • search/ control panel, search bar, search panel, …

  • webclient/ the web client specific code: navbar, user menu, action service, …

The web/static/src is the root folder. Everything inside can simply be imported by using the @web prefix. For example, here is how one can import the memoize function located in web/static/src/core/utils/functions:

import { memoize } from "@web/core/utils/functions";

WebClient Architecture

As mentioned above, the web client is an owl application. Here is a slightly simplified version of its template:

<t t-name="web.WebClient" owl="1">
    <body class="o_web_client">

As we can see, it basically is a wrapper for a navbar, the current action and some additional components. The ActionContainer is a higher order component that will display the current action controller (so, a client action, or a specific view in the case of actions of type act_window). Managing actions is a huge part of its work: the action service keeps in memory a stack of all active actions (represented in the breadcrumbs), and coordinates each change.

Another interesting thing to note is the MainComponentsContainer: it is simply a component that displays all components registered in the main_components registry. This is how other parts of the system can extend the web client.


As an Owl application, the Flectra web client defines its own environment (components can access it using this.env). Here is a description of what Flectra adds to the shared env object:




required by Owl (contains all templates)


main bus, used to coordinate some generic events


all deployed services (should usually be accessed with the useService hook)


string. If non empty, the web client is in debug mode


translation function


boolean. If true, the web client is currently in mobile mode (screen width <= 767px)

So, for example, to translate a string in a component (note: templates are automatically translated, so no specific action is required in that case), one can do this:

const someString = this.env._t('some text');


Having a reference to the environment is quite powerful, because it provides access to all services. This is useful in many cases: for example, user menu items are mostly defined as a string, and a function taking the env as unique argument. This is enough to express all user menu needs.

Building Blocks

Most of the web client is built with a few types of abstractions: registries, services, components and hooks.


Registries are basically a simple key/value mapping that stores some specific kind of objects. They are an important part of the extensibility of the UI: once some object is registered, the rest of the web client can use it. For example, the field registry contains all field components (or widgets) that can be used in views.

import { registry } from "./core/registry";

class MyFieldChar extends owl.Component {
    // some code

registry.category("fields").add("my_field_char", MyFieldChar);

Note that we import the main registry from @web/core/registry then open the sub registry fields.


Services are long lived pieces of code that provide a feature. They may be imported by components (with useService) or by other services. Also, they can declare a set of dependencies. In that sense, services are basically a DI (dependency injection) system. For example, the notification service provides a way to display a notification, or the rpc service is the proper way to perform a request to the Flectra server.

The following example registers a simple service that displays a notification every 5 second:

import { registry } from "./core/registry";

const myService = {
    dependencies: ["notification"],
    start(env, { notification }) {
        let counter = 1;
        setInterval(() => {
            notification.add(`Tick Tock ${counter++}`);
        }, 5000);

serviceRegistry.add("myService", myService);

Components and Hooks

Components and hooks are ideas coming from the Owl component system. Flectra components are simply owl components that are part of the web client.

Hooks are a way to factorize code, even if it depends on lifecycle. This is a composable/functional way to inject a feature in a component. They can be seen as a kind of mixin.

function useCurrentTime() {
    const state = useState({ now: new Date() });
    const update = () => = new Date();
    let timer;
    onWillStart(() => timer = setInterval(update, 1000));
    onWillUnmount(() => clearInterval(timer));
    return state;


An important concept in the Flectra javascript is the context: it provides a way for code to give more context to a function call or a rpc, so other parts of the system can properly react to that information. In some way, it is like a bag of information that is propagated everywhere. It is useful in some situations, such as letting the Flectra server know that a model rpc comes from a specific form view, or activating/disabling some features in a component.

There are two different contexts in the Flectra web client: the user context and the action context (so, we should be careful when using the word context: it could mean a different thing depending on the situation).


The context object may be useful in many cases, but one should be careful not to overuse it! Many problems can be solved in a standard way without modifying the context.

User Context

The user context is a small object containing various informations related to the current user. It is available through the user service:

class MyComponent extends Component {
    setup() {
        const user = useService("user");

It contains the following information:






the list of active company ids for the user



the user language code (such as “en_us”)



the user current timezone (for example “Europe/Brussels”)

In practice, the orm service automatically adds the user context to each of its requests. This is why it is usually not necessary to import it directly in most cases.


The first element of the allowed_company_ids is the main company of the user.

Action Context

The ir.actions.act_window and ir.actions.client support an optional context field. This field is a char that represents an object. Whenever the corresponding action is loaded in the web client, this context field will be evaluated as an object and given to the component that corresponds to the action.

<field name="context">{'search_default_customer': 1}</field>

It can be used in many different ways. For example, the views add the action context to every requests made to the server. Another important use is to activate some search filter by default (see example above).

Sometimes, when we execute new actions manually (so, programmatically, in javascript), it is useful to be able to extend the action context. This can be done with the additional_context argument.

// in setup
let actionService = useService("action");

// in some event handler
actionService.doAction("addon_name.something", {
        default_period_id: defaultPeriodId

In this example, the action with xml_id addon_name.something will be loaded, and its context will be extended with the default_period_id value. This is a very important usecase that lets developers combine actions together by providing some information to the next action.

Python Interpreter

The Flectra framework features a built-in small python interpreter. Its purpose is to evaluate small python expressions. This is important, because views in Flectra have modifiers written in python, but they need to be evaluated by the browser.


import { evaluateExpr } from "@web/core/py_js/py";

evaluateExpr("1 + 2*{'a': 1}.get('b', 54) + v", { v: 33 }); // returns 142

The py javascript code exports 5 functions:

  • expr (string()) – the expression to tokenize


Token[] a list of token

  • tokens (Token[]()) – a list of tokens


AST an abstract syntax tree structure representing the expression

  • expr (string()) – a string representing a valid python expression


AST an abstract syntax tree structure representing the expression

evaluate(ast[, context])
  • ast (AST()) – a AST structure that represents an expression

  • context (Object()) – an object that provides an additional evaluation context


any the resulting value of the expression, with respect to the context

evaluateExpr(expr[, context])
  • expr (string()) – a string representing a valid python expression

  • context (Object()) – an object that provides an additional evaluation context


any the resulting value of the expression, with respect to the context


Broadly speaking, domains in Flectra represent a set of records that matches some specified conditions. In javascript, they are usually represented either as a list of conditions (or of operators: |, & or ! in prefix notation), or as string expressions. They don’t have to be normalized (the & operator is implied if necessary). For example:

// list of conditions
[["a", "=", 3]]
[["a", "=", 1], ["b", "=", 2], ["c", "=", 3]]
["&", "&", ["a", "=", 1], ["b", "=", 2], ["c", "=", 3]]
["&", "!", ["a", "=", 1], "|", ["a", "=", 2], ["a", "=", 3]]

// string expressions
"[('some_file', '>', a)]"
"[('date','>=', (context_today() - datetime.timedelta(days=30)).strftime('%Y-%m-%d'))]"
"[('date', '!=', False)]"

String expressions are more powerful than list expressions: they can contain python expressions and unevaluated values, that depends on some evaluation context. However, manipulating string expressions is more difficult.

Since domains are quite important in the web client, Flectra provides a Domain class:

new Domain([["a", "=", 3]]).contains({ a: 3 }) // true

const domain = new Domain(["&", "&", ["a", "=", 1], ["b", "=", 2], ["c", "=", 3]]);
domain.contains({ a: 1, b: 2, c: 3 }); // true
domain.contains({ a: -1, b: 2, c: 3 }); // false

// next expression returns ["|", ("a", "=", 1), ("b", "<=", 3)]
Domain.or([[["a", "=", 1]], "[('b', '<=', 3)]"]).toString();

Here is the Domain class description:

class Domain([descr])
  • descr (string | any[] | Domain()) – a domain description

  • record (Object()) – a record object



Returns true if the record matches all the condition specified by the domain



Returns a string description for the domain

  • context (Object()) – evaluation context



Returns a list description for the domain. Note that this method takes an optional context object that will be used to replace all free variables.

new Domain(`[('a', '>', b)]`).toList({ b:3 }); // [['a', '>', 3]]

The Domain class also provides 4 useful static methods to combine domains:

// ["&", ("a", "=", 1), ("uid", "<=", uid)]
Domain.and([[["a", "=", 1]], "[('uid', '<=', uid)]"]).toString();

// ["|", ("a", "=", 1), ("uid", "<=", uid)]
Domain.or([[["a", "=", 1]], "[('uid', '<=', uid)]"]).toString();

// ["!", ("a", "=", 1)]
Domain.not([["a", "=", 1]]).toString();

// ["&", ("a", "=", 1), ("uid", "<=", uid)]
Domain.combine([[["a", "=", 1]], "[('uid', '<=', uid)]"], "AND").toString();
static Domain.and(domains)

domains (string[] | any[][] | Domain[]) – a list of domain representations



Returns a domain representing the intersection of all domains.

static Domain.or(domains)

domains (string[] | any[][] | Domain[]) – a list of domain representations



Returns a domain representing the union of all domains.

static Domain.not(domain)

domain (string | any[] | Domain) – a domain representation



Returns a domain representing the negation of the domain argument

static Domain.combine(domains, operator)
  • domains (string[] | any[][] | Domain[]) – a list of domain representations

  • operator ('AND' or 'OR') – an operator



Returns a domain representing either the intersection or the union of all the domains, depending on the value of the operator argument.


The web client environment object contains an event bus, named bus. Its purpose is to allow various parts of the system to properly coordinate themselves, without coupling them. The env.bus is an owl EventBus, that should be used for global events of interest.

// for example, in some service code:
env.bus.on("WEB_CLIENT_READY", null, doSomething);

Here is a list of the events that can be triggered on this bus:





a mode indicating what part of the ui has been updated (‘current’, ‘new’ or ‘fullscreen’)

the rendering of the action requested to the action manager is done


next rendering info

the action manager has finished computing the next interface



the menu service’s current app has changed



the url hash was changed


rpc id

a rpc request has just started


rpc id

a rpc request is completed



the web client has been mounted



the main view should focus itself



all internal caches should be cleared


list of functions

all views with uncommitted changes should clear them, and push a callback in the list

Browser Object

The javascript framework also provides a special object browser that provides access to many browser APIs, like location, localStorage or setTimeout. For example, here is how one could use the browser.setTimeout function:

import { browser } from "@web/core/browser/browser";

// somewhere in code
browser.setTimeout(someFunction, 1000);

It is mostly interesting for testing purposes: all code using the browser object can be tested easily by mocking the relevant functions for the duration of the test.

It contains the following content:




















Debug mode

Flectra can sometimes operate in a special mode called the debug mode. It is used for two main purposes:

  • display additional information/fields for some particular screens,

  • provide some additional tools to help developer debug the Flectra interface.

The debug mode is described by a string. An empty string means that the debug mode is not active. Otherwise, it is active. If the string contains assets or tests, then the corresponding specific sub modes are activated (see below). Both modes can be active at the same time, for example with the string assets,tests.

The debug mode current value can be read in the environment: env.debug.


To show menus, fields or view elements only in debug mode, you should target the group base.group_no_one:

<field name="fname" groups="base.group_no_one"/>

Assets mode

The debug=assets sub mode is useful to debug javascript code: once activated, the assets bundles are no longer minified, and source-maps are generated as well. This makes it useful to debug all kind of javascript code.

Tests mode

There is another sub mode named tests: if enabled, the server injects the bundle web.assets_tests in the page. This bundle contains mostly test tours (tours whose purpose is to test a feature, not to show something interesting to users). The tests mode is then useful to be able to run these tours.

See also