---
title: "05. Configuration"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{05 - Configuration}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  purl = FALSE
)
library(golem)
x <- file.path(
  tempdir(),
  "golex"
)
unlink(x, TRUE, TRUE)

x <- golem::create_golem(x, package_name = "golex", open = FALSE)
old <- setwd(x)
knitr::opts_knit$set(root.dir = x)
```

```{r setup}
library(golem)
```

```{r echo = FALSE}
old <- setwd(x)
```

## Two Ways to Manage Production vs Development Mode

`{golem}` provides two separate mechanisms for managing production and development modes in your Shiny applications:

1. **R Options Approach**: Using `options(golem.app.prod = TRUE/FALSE)` which is checked by `app_prod()` and `app_dev()` functions. This approach controls the behavior of `{golem}`'s development-aware utility functions like `cat_dev()`, `print_dev()`, `message_dev()`, and similar tools.

2. **Configuration File Approach**: Using the `golem-config.yml` file to store configuration values (including an `app_prod` setting) that can be retrieved in your application code using `get_golem_config()`.

**Important**: These two mechanisms are independent and serve different purposes. The R option controls `{golem}`'s built-in development tools, while the config file provides a flexible way to store and retrieve application-specific settings. This vignette focuses on the configuration file approach.

## 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}`](https://github.com/rstudio/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 golem::pkg_path()
```

+ default/golem_name, default/golem_version, default/app_prod can be used across the whole life of your `{golem}` app: while developing, and also when in production.
+ production/app_prod can be used to add 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:

```{r}
set_golem_options()
```

```{r echo = FALSE, comment= "", }
cat(
  sep = "\n",
  readLines(
    "inst/golem-config.yml"
  )
)
```

The functions reading the options in this config file are:

```{r}
get_golem_name()
get_golem_wd()
get_golem_version()
```

You can set these with:

```{r eval = FALSE}
set_golem_name("this")
set_golem_wd(".")
set_golem_version("0.0.1")
```

```{r echo = FALSE, comment= "", }
cat(
  sep = "\n",
  readLines(
    "inst/golem-config.yml"
  )
)
```


## 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.

```{r}
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:

```{r echo = FALSE, comment= ""}
cat(
  sep = "\n",
  readLines(
    file.path(x, "inst/golem-config.yml")
  )
)
```

## `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:

```{r}
pkgload::load_all()
get_golem_config(
  "where"
)
get_golem_config(
  "where",
  config = "production"
)
```

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

```{r}
Sys.setenv("R_CONFIG_ACTIVE" = "production")
get_golem_config("where")
```

## `golem_config` vs `golem_options`

There are two ways to configure golem apps:

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

The main 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 backend, and will not be linked to the parameters passed to `run_app()` (even if this is technically possible, this is not the main objective).

The `golem-config.yml` file is also linked to the `R_CONFIG_ACTIVE` environment variable, just as any `{config}` file.

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

## Connecting Back to the R Options Approach

As mentioned at the beginning of this vignette, `{golem}` uses two separate mechanisms for production/development configuration. While this vignette has focused on the `golem-config.yml` file, it's important to understand how this relates to the R options approach.

### The R Options Mechanism

The R option `options(golem.app.prod)` is used by `{golem}`'s development-aware functions:

- `app_prod()` - Returns `TRUE` if the app is in production mode
- `app_dev()` - Returns `TRUE` if the app is in development mode
- Development-only output functions: `cat_dev()`, `print_dev()`, `message_dev()`, `warning_dev()`, `browser_dev()`

These functions check `getOption("golem.app.prod")` directly and do not read from the config file.

### Important: The Two Mechanisms Are Independent

The `app_prod` value in `golem-config.yml` and the `options(golem.app.prod)` R option are **not automatically synchronized**. They serve different purposes:

- **Config file `app_prod`**: A persistent configuration value that you can retrieve using `get_golem_config("app_prod")` to use in your own application logic. This value can vary by environment (default, production, dev) using the `R_CONFIG_ACTIVE` environment variable.

- **R option `golem.app.prod`**: A session-level setting that controls `{golem}`'s built-in development tools. This must be explicitly set in your code or launch configuration (e.g., in Docker CMD or `run_dev.R`).

### Best Practices

- **Set the R option explicitly**: When deploying to production, ensure you set `options(golem.app.prod = TRUE)` in your app's launch script or Docker configuration. The `{golem}` Dockerfile templates handle this automatically.

- **Use the config file for your app's logic**: If you need environment-specific configuration in your application code (e.g., different API endpoints for dev vs production), use `get_golem_config()` to retrieve values from `golem-config.yml`.

- **Keep them in sync if needed**: If you want the config file's `app_prod` setting to match your R option, you'll need to manage this synchronization in your own code. For example, in your `run_app()` function, you could set the option based on the config value:

```r
# Example: sync config to R option (optional)
if (get_golem_config("app_prod")) {
  options(golem.app.prod = TRUE)
}
```

## 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}`.

```{r echo = FALSE}
setwd(old)
```
