# Using golem config

    library(golem)

## About `inst/golem-config.yml`

When you start a new `{golem}` application, you’ll find a file called `golem-config.yml` in the `inst/` folder.

By default, this file contains the name of your app, its version, and the default working directory (which is the root of your package).

This config file is based on the `{config}` format, which allows you to create configuration files for different application contexts. Please refer to this package documentation for more information.

## Setting `golem-config`

Here is what the default config file looks like:

    default:
      golem_name: golex
      golem_version: 0.0.0.9000
      app_prod: no
    production:
      app_prod: yes
    dev:
      golem_wd: !expr here::here()

- default/golem_name, default/golem_version, default/app_prod are usable across the whole life of your golem app: while developing, and also when in production.
- production/app_prod might be used for adding elements that are to be used once the app is in production.
- dev/golem_wd is in a `dev` config because the only moment you might reliably use this config is while developing your app. Use the `app_sys()` function if you want to rely on the package path once the app is deployed.

The good news is that if you don’t want/need to use `{config}`, you can safely ignore this file, just leave it where it is: it is used internally by the `{golem}` functions.

These options are globally set with:

    set_golem_options()
    #> ── Setting {golem} options in `golem-config.yml` ─────────
    #> ✓ Setting `golem_wd` to here::here()
    #> You can change golem working directory with set_golem_wd('path/to/wd')
    #> ✓ Setting `golem_name` to golex
    #> ✓ Setting `golem_version` to 0.0.0.9000
    #> ✓ Setting `app_prod` to FALSE
    #> ── Setting {usethis} project as `golem_wd` ───────────────
    #> ✔ Setting active project to '/private/var/folders/5z/rm2h62lj45d332kfpj28c8zm0000gn/T/Rtmpc84Nw3/golex'

The functions reading the options in this config file are:

    get_golem_name()
    #> [1] "golex"
    get_golem_wd()
    #> [1] "/private/var/folders/5z/rm2h62lj45d332kfpj28c8zm0000gn/T/Rtmpc84Nw3/golex"
    get_golem_version()
    #> [1] "0.0.0.9000"

You can set these with:

    set_golem_name("this")
    set_golem_wd(".")
    set_golem_version("0.0.1")

## Using `golem-config`

If you’re already familiar with the `{config}` package, you can use this file just as any config file.

`{golem}` comes with an `amend_golem_config()` function to add elements to it.

    amend_golem_config(
      key = "where",
      value = "indev"
    )
    amend_golem_config(
      key = "where",
      value = "inprod",
      config = "production"
    )

Will result in a `golem-config.yml` file as such:

    default:
      golem_name: golex
      golem_version: 0.0.0.9000
      app_prod: no
      where: indev
    production:
      app_prod: yes
      where: inprod
    dev:
      golem_wd: /private/var/folders/5z/rm2h62lj45d332kfpj28c8zm0000gn/T/Rtmpc84Nw3/golex

## `app_config.R`

In `R/app_config.R`, you’ll find a `get_golem_config()` function that allows you to retrieve config from this config file:

    pkgload::load_all()
    #> Loading golex
    get_golem_config(
      "where"
    )
    #> [1] "indev"
    get_golem_config(
      "where",
      config = "production"
    )
    #> [1] "inprod"

Or using the env var (default `{config}` behavior):

    Sys.setenv("R_CONFIG_ACTIVE" = "production")
    get_golem_config("where")
    #> [1] "inprod"

## `golem_config` vs `golem_options`

There is two ways to configure golem apps:

- The `golem_opts` in the `run_app()` function
- The `golem-config.yml` file

The big difference between these two is that the golem options from `run_app()` are meant to be configured during runtime: you’ll be doing `run_app(val = "this")`, whereas the `golem-config` is meant to be used in the back-end, and will not be linked to the parameters passed to `run_app()` (even if this is technically possible, this is not the main objective),.

It’s also linked to the `R_CONFIG_ACTIVE` environment variable, just as any `{config}` file.

The idea is also that the `golem-config.yml` file is shareable across `{golem}` projects (`golem_opts` are application specific), and will be tracked by version control systems.

## Note for `{golem}` < 0.2.0 users

If you’ve built an app with `{golem}` before the version 0.2.0, this config file doesn’t exist: you’ll be prompted to create it if you update a newer version of `{golem}`.