Clarify when local_app_support() is needed vs package functions

[Copilot]

Users were unclear when local_app_support() is required, particularly for inline apps where package functions are already available via library() or devtools::load_all().

Changes

Roxygen documentation (R/test-app.R)

• Added sections distinguishing inline apps (no local_app_support() needed) from directory-based apps (needed)
• Clarified differences between local_app_support(), with_app_support(), and load_app_support()
• Expanded examples to cover real-world scenarios

Vignette (vignettes/use-package.Rmd)

• New section "Understanding app support files" with decision tree for function selection
• Code examples showing when each approach applies

FAQ (vignettes/zzz-faq.Rmd)

• Added note that inline apps don't require app support functions
• Cross-reference to detailed vignette section

Example

This does not need local_app_support():

test_that("inline app with package modules works", {
  # mod_test_ui already available from package
  test_app <- shinyApp(
    ui = fluidPage(mod_test_ui("test")),
    server = function(input, output, session) {
      mod_test_server(id = "test")
    }
  )
  app <- AppDriver$new(test_app)
})

This does need it:

test_that("app with separate support files", {
  app_dir <- system.file("myapps/app1", package = "mypkg")
  local_app_support(app_dir)  # Loads app1/R/*.R files
  
  expect_true(exists("my_module_ui"))  # From app1/R/
  app <- AppDriver$new(app_dir)
})

Original prompt

---

This section details on the original issue you should resolve

<issue_title>How to use local_app_support() with AppDriver</issue_title>
<issue_description>Hello,

I have a shiny app that I want to test as part of a package. The app uses package functions, but currently I"m getting an error that the package is not found during test because it's not installed but loaded with devtools.

I read that the new local_app_support() function is designed to help here, but I don't know how to use it with a test app and the app driver. For example

# App with modules
testApp <- shinyApp(
    ui <- fluidPage(
      mod_test_ui("test")
    ),
    server <- function(input, output, session) {
      mod_test_server(id = "test")
    }
  )

# Start app and click option 4
app <- AppDriver$new(app = testApp)
app$set_inputs("test-option" = "4")

This is not a fully reproducible example because you'd need the whole package, but where in this code do I add local_app_support() such that I don't get the error: "packagename" not found, during testing. local_app_support requires an app_dir argument, but I don't have that given my app is passed as a variable to the AppDriver.

I hope I made the issue clear, but feel free to ask for more details!

Thanks</issue_description>

<agent_instructions>Expand upon the documentation so there is no doubt in the benefits.

Expand upon the vignette usage for the app support methods.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@schloerke @pieterjanvc Thank you for your patience! I hope this write up helps with the confusion. I'll adjust the issue to request better docs.

---

When using inline apps like in your example, there is no need for local_app_support() as you can get access to anything you need by rearranging your helper functions. Ex, your mod_test_ui would be within the test file or your package and you could test it directly.

So, hopefully no need for local_app_supprt() when writing inline tests

---

However, Let's imagine your file structure looks like:

# File: ./inst/myapps/app1/R/app.R

app1_ui <- fluidPage(my_module_ui("test"))
app1_server <- function(input, output, session) {
  mod_test_server(id = "test")
}

shinyApp(ui = app1_ui, server = app1_server)

# File: ./inst/myapps/app1/R/mymods.R
mod_test_ui <- #.... actually put code here ...
mod_test_server <- #.... actually put code here ...

You can add a test file for your package that attempts to access the test app information without clobbering your whole test file.

Ex test file within {mypkg}'s tests:

# File: ./tests/testthat/test-app1.R

# Does NOT exist
expect_true(!exists("my_module_ui"))

test_that("app1 loads default values", {

  # Does NOT exist
  expect_true(!exists("my_module_ui"))

  local_app_support(system.file("myapps/app1", package = "mypkg"))

  # DOES exist ; <-- Goal achieved!
  expect_true(exists("my_module_ui"))

})

# Does NOT exist
expect_true(!exists("my_module_ui"))

---

For an internal test example... this test looks for a test app and loads its supporting files into the local() call:

shinytest2/tests/testthat/test-test-app.R

Lines 1 to 13 in b6014c8

	test_that("app support loading works", {
	skip_if_no_apps()
	expect_false(exists("n"))
	local({
	local_app_support(app_dir = test_path("apps/wait"))
	expect_true(exists("n"))
	expect_equal(n, 750)
	})
	expect_false(exists("n"))
	})

which loads this value:

shinytest2/tests/testthat/apps/wait/R/n.R

Line 4 in b6014c8

n <- 750

---

Related... An internal test showing that internal and exported package values are available in different contexts.

Values:

shinytest2/tests/testthat/pkgs/expkg/R/value.R

Lines 1 to 5 in b6014c8

	expkg_internal_value <- "expkg internal value"
	#' Exported docs
	#' @export
	expkg_exported_value <- "expkg exported value"

Availability:

• In testing: both values readily available.
  

  shinytest2/tests/testthat/pkgs/expkg/tests/testthat/test-pkg.R

  Lines 3 to 9 in b6014c8

  	test_that("Local pkg loads", {
  	# No library calls!
  	# expkg should be auto loaded by testthat
  	expect_equal(expkg_internal_value, "expkg internal value")
  	expect_equal(expkg_exported_value, "expkg exported value")
  	})

• Within app: Neither value is available until a library() or require() call within your app.

  shinytest2/tests/testthat/pkgs/expkg/tests/testthat/apps/require/app.R

  Lines 16 to 23 in b6014c8

  	testthat::expect_false(exists("expkg_exported_value"))
  	testthat::expect_true(require(expkg)) # This also attaches the package
  	testthat::expect_true(is.function(expkg_shiny_app))
  	testthat::expect_equal(expkg_exported_value, "expkg exported value")
  	testthat::expect_false(exists("expkg_internal_value"))
  	testthat::expect_equal(expkg:::expkg_internal_value, "expkg internal value")

• Fixes How to use local_app_support() with AppDriver #431

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@copilot Add news bullet. Your PR is 438

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@copilot Resolve these suggestions.