Add support for overriding the installation directory (#45)

docs/changelog.md

@@ -8,6 +8,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## Unreleased
 
+***Added:***
+
+- Add support for overriding the installation directory
+
 ***Fixed:***
 
 - Properly handle cases where options contain line feed characters

docs/runtime.md

@@ -68,6 +68,10 @@ To provide consistent behavior on each user's machine:
 
 A single environment variable called `PYAPP` is injected with the value of `1` ([by default](config.md#installation-indicator)) when running applications and may be used to detect this mode of installation versus others.
 
+## Location
+
+The default location of your application's installation differs based on the operating system and can be overridden at runtime with the `PYAPP_INSTALL_DIR_<PROJECT_NAME>` environment variable where `<PROJECT_NAME>` is the uppercased version of the [project name](config.md#project).
+
 ## Commands
 
 Built applications have a single top-level command group named `self` ([by default](config.md#management-command)) and all other invocations will be forwarded to your actual [execution logic](config.md#execution-mode).

src/app.rs

@@ -28,11 +28,20 @@ pub fn initialize() -> Result<()> {
         .set(platform_directories)
         .expect("could not set platform directories");
 
-    let installation_directory = platform_dirs()
-        .data_local_dir()
-        .join(project_name())
-        .join(distribution_id())
-        .join(project_version());
+    let install_dir_override = env::var(format!(
+        "PYAPP_INSTALL_DIR_{}",
+        project_name().to_uppercase()
+    ))
+    .unwrap_or_default();
+    let installation_directory = if !install_dir_override.is_empty() {
+        PathBuf::from(install_dir_override)
+    } else {
+        platform_dirs()
+            .data_local_dir()
+            .join(project_name())
+            .join(distribution_id())
+            .join(project_version())
+    };
     INSTALLATION_DIRECTORY
         .set(installation_directory)
         .expect("could not set installation directory");