feat(install): add use flag (Schniz#1435)

* feat(install): add `--use` flag

* add changeset

* update the command docs

---------

Co-authored-by: Gal Schlezinger <gal@spitfire.co.il>

Author: SunsetTechuila

.changeset/grumpy-dingos-turn.md

@@ -0,0 +1,5 @@
+---
+"fnm": minor
+---
+
+add `use` flag to the `install` command

docs/commands.md

@@ -262,6 +262,9 @@ Options:
           [default: info]
           [possible values: quiet, error, info]
 
+      --use
+          Use the installed version immediately after installation
+
       --arch <ARCH>
           Override the architecture of the installed Node binary. Defaults to arch of fnm binary
 

src/commands/install.rs

@@ -1,4 +1,5 @@
 use super::command::Command;
+use super::r#use::Use;
 use crate::alias::create_alias;
 use crate::arch::get_safe_arch;
 use crate::config::FnmConfig;
@@ -8,6 +9,7 @@ use crate::outln;
 use crate::progress::ProgressConfig;
 use crate::remote_node_index;
 use crate::user_version::UserVersion;
+use crate::user_version_reader::UserVersionReader;
 use crate::version::Version;
 use crate::version_files::get_user_version_for_directory;
 use colored::Colorize;
@@ -32,6 +34,10 @@ pub struct Install {
     #[clap(long, default_value_t)]
     #[arg(value_enum)]
     pub progress: ProgressConfig,
+
+    /// Use the installed version immediately after installation
+    #[clap(long)]
+    pub r#use: bool,
 }
 
 impl Install {
@@ -66,6 +72,7 @@ impl Command for Install {
     fn apply(self, config: &FnmConfig) -> Result<(), Self::Error> {
         let current_dir = std::env::current_dir().unwrap();
         let show_progress = self.progress.enabled(config);
+        let use_installed = self.r#use;
 
         let current_version = self
             .version()?
@@ -165,6 +172,10 @@ impl Command for Install {
             enable_corepack(&version, config)?;
         }
 
+        if use_installed {
+            use_installed_version(&version, config)?;
+        }
+
         Ok(())
     }
 }
@@ -194,6 +205,21 @@ fn enable_corepack(version: &Version, config: &FnmConfig) -> Result<(), Error> {
     Ok(())
 }
 
+fn use_installed_version(version: &Version, config: &FnmConfig) -> Result<(), Error> {
+    Use {
+        version: Some(UserVersionReader::Direct(UserVersion::Full(
+            version.clone(),
+        ))),
+        install_if_missing: false,
+        silent_if_unchanged: false,
+    }
+    .apply(config)
+    .map_err(|source| Error::UseError {
+        source: Box::new(source),
+    })?;
+    Ok(())
+}
+
 #[derive(Debug, Error)]
 pub enum Error {
     #[error("Can't download the requested binary: {}", source)]
@@ -208,6 +234,10 @@ pub enum Error {
         #[from]
         source: super::exec::Error,
     },
+    #[error(transparent)]
+    UseError {
+        source: Box<<Use as Command>::Error>,
+    },
     #[error("Can't find version in dotfiles. Please provide a version manually to the command.")]
     CantInferVersion,
     #[error(transparent)]
@@ -244,6 +274,7 @@ mod tests {
             lts: false,
             latest: false,
             progress: ProgressConfig::Never,
+            r#use: false,
         }
         .apply(&config)
         .expect("Can't install");
@@ -270,6 +301,7 @@ mod tests {
             lts: false,
             latest: true,
             progress: ProgressConfig::Never,
+            r#use: false,
         }
         .apply(&config)
         .expect("Can't install");

src/commands/use.rs

@@ -16,15 +16,15 @@ use thiserror::Error;
 
 #[derive(clap::Parser, Debug)]
 pub struct Use {
-    version: Option<UserVersionReader>,
+    pub version: Option<UserVersionReader>,
     /// Install the version if it isn't installed yet
     #[clap(long)]
-    install_if_missing: bool,
+    pub install_if_missing: bool,
 
     /// Don't output a message identifying the version being used
     /// if it will not change due to execution of this command
     #[clap(long)]
-    silent_if_unchanged: bool,
+    pub silent_if_unchanged: bool,
 }
 
 impl Command for Use {