Configuration Values

You can check and set the configuration values in frontend/Config.ts.

The table below describes the configuration values for the Lexicon Mobile App.

If there is a default value indicated, you do not need to set it.

Variable	Required	Notes	Default Value	Example Value(s)
proseUrl	Yes	The url of the Prose Server (must start with http or https)	-	https://prose.myserver.com https://prose.myserver.com:8080 https://prose.myserver.com/subpath https://prose.myserver.com:8080/subpath
inferDevelopmentHost	No	The flag (true / false) to override localhost with the host of the development machine	(empty)	true

The config object

In the Config.ts file, you'll find a config object that allows you to specify configuration values by scenario.

The two primary scenarios are:

• localDevelopment: when developing against the app locally. This configuration is also used as a fallback for an unknown build channel.
• buildChannels: used to define configuration by build channel when building the app with the EAS CLI.

Primarily, you'll only be concerned with configuring proseUrl for each of these sections.

proseUrl

caution

proseUrl must always be specified, with or without a port number, and must always start with either http:// or https://.

proseUrl is used to specify the URL of the Prose GraphQL API.

The Prose GraphQL API acts a middleman between the Lexicon Mobile App and your Discourse instance. Without it, the mobile app cannot interact with your Discourse instance.

Example

const config = {
  localDevelopment: {
    proseUrl: 'http://localhost:8929',
  },
  buildChannels: {
    preview: {
      proseUrl: 'https://preview.myserver.com',
    },
    production: {
      proseUrl: 'https://prose.myserver.com',
    },
  },
};

With this configuration above, the app will:

• point at http://localhost:8929 when you run the app using npm run start
• point at https://preview.myserver.com when you build the app using eas build --profile preview
• point at https://prose.myserver.com when you build the app using eas build

proseUrl also can include a subpath if desired:

const config = {
  localDevelopment: {
    proseUrl: 'http://localhost:8929',
  },
  buildChannels: {
    preview: {
      proseUrl: 'https://preview.myserver.com:8080/subpath',
    },
    production: {
      proseUrl: 'https://myserver.com/api/prose',
    },
  },
};

Different Behavior in Development

When running the app locally, if proseUrl is set to http://localhost or http://127.0.0.1, it will replace proseUrl with the IP address of your development machine. It does this by using Expo's debuggerHost constant.

Note: this does not apply when building the app.

This addresses multiple issues:

• Accessing localhost from within the Android simulator does not map to your development machine
• Accessing localhost from a device running Expo Go does not map to your development machine

Both of these scenarios would otherwise require you to manually identify and specify your development machine's IP address with proseUrl. This is bothersome since your machine's IP address can change over time.

If you are interested in more details about this, the implementation of this behavior is available in frontend/constants/app.ts.

This behavior of automatically overriding those values can be disabled, with inferDevelopmentHost, which is covered below.

inferDevelopmentHost

info

This flag is only valid under localDevelopment. It has no effect when used as part of buildChannels.

When in development, by default, the Lexicon Mobile App will check to see if proseUrl is set to either http://localhost or http://127.0.0.1.

When detected, either of those values will be overwritten with the IP address of your development machine.

This is a very useful feature that makes on-device testing simply work out of the box without needing to manually specify your IP address (or update it when it changes).

For scenarios where this behavior is not desirable, inferDevelopmentHost can be used as a flag to disable this behavior. It can be disabled by specifying the value as false.

When set to false, this behavior of overriding proseUrl with the development machine's IP address will no longer occur, and the original value will be passed through as-is.

const config = {
  localDevelopment: {
    proseUrl: 'http://localhost:8929',
    inferDevelopmentHost: false,
  },
};