Skip to contents

shooters

shooters provides static-analysis utilities for Shiny applications. The flagship function, ns_tree(), parses R source files in a directory and prints a plain-text call tree showing how functions relate to one another — with no need to run the app.

Installation 

# install.packages("pak")
pak::pak("mjfrigaard/shooters")

Usage

Point ns_tree() at any directory that contains R source files:

ns_tree("R")

Example apps

shooters bundles four example apps that cover the most common Shiny structural patterns.

apps <- system.file("apps", package = "shooters")

minimal — bare ui / server

No wrapper functions and no modules. ui is a plain object; server is the only defined function. Use ui_fun / server_fun to tell ns_tree() what to look for:

ns_tree(file.path(apps, "minimal"), ui_fun = "ui", server_fun = "server")
#> █─(app)
#> └─█─server

no_modules — helper functions, no modules

A launch() entry point calls app_ui() and app_server(). The server delegates to two plain helper functions:

ns_tree(file.path(apps, "no_modules"))
#> █─launch
#> ├─█─app_ui
#> └─█─app_server
#>   ├─█─make_data
#>   └─█─render_scatter

single_module — one NS / moduleServer pair

A scatter-plot module (scatter_ui / scatter_server) is nested inside the app-level UI and server:

ns_tree(file.path(apps, "single_module"))
#> █─launch
#> ├─█─app_ui
#> │ └─█─scatter_ui
#> └─█─app_server
#>   └─█─scatter_server

nested_modules — modules calling other modules

A display parent module delegates to plot and table child modules, spread across multiple files:

ns_tree(file.path(apps, "nested_modules"))
#> █─launch
#> ├─█─app_ui
#> │ └─█─display_ui
#> │   ├─█─plot_ui
#> │   └─█─table_ui
#> └─█─app_server
#>   └─█─display_server
#>     ├─█─plot_server
#>     └─█─table_server

How it works

ns_tree() operates in four steps:

  1. Parse every .R file in the target directory with parse().
  2. Extract top-level function definitions (name <- function(...)).
  3. Walk each function body to find references to other locally defined functions, building a call graph.
  4. Render the call graph as a depth-first ASCII tree, starting from the app root.

The root is resolved with a three-tier fallback:

Tier Condition Root used
1 app_fun (default "launch") is defined That function
2 ui_fun or server_fun is defined Co-roots under (app)
3 None of the above All defined functions under (app)

Demo apps

Run any of the bundled example apps interactively:

run_demo()                    # nested_modules (default)
run_demo("single_module")
run_demo("no_modules")
run_demo("minimal")