From 4951311cdab723bc59908163f296745c65e0988b Mon Sep 17 00:00:00 2001
From: Frederik Delaere <frederik.delaere@ugent.be>
Date: Thu, 3 Oct 2019 21:14:50 +0200
Subject: [PATCH] when passing no argument to module cd, then switch the cwd to
 the one of the last loaded module

---
 README.md        |  3 ++-
 src/main.rs      | 24 +++++++++++++++++++++++-
 src/rsmodules.rs |  8 ++++++--
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 7c090e2..8c34e40 100755
--- a/README.md
+++ b/README.md
@@ -66,7 +66,8 @@ D perl/5.14.1 | Perl 5.14.1 is a highly capable, feature-rich programming langua
  * ```module autoload append|prepend|remove|list|purge [modulename(s)]``` Manages the auto loading of modules by adding them to your startup scripts.
  * ```module delete [modulename(s)]``` Deletes one or more modulefiles. But only if you have the permissions to do so.
  * ```module readme [modulename]``` Looks for a manpage or README file in the module installation folder and displays the contents of this file.
- * ```module cd [modulename]``` Changes your current working directory to the module installation folder.
+ * ```module cd [modulename]``` Changes your current working directory to the module installation folder. When you don't provide a modulename
+      the working directory is changed to the module installation folder of the last loaded module.
  * ```module edit [modulename]``` Opens the modulefile in your $EDITOR or if this variable is not present in ```vi -e```.
  * The output is not redirected to stderr, but to stdout. So you are able to use grep / rg on the output and it doesn't trigger errors in pipelines.
  * RSModules is fast because it's written in a compiled language and it is using cache files for listing the modules.
diff --git a/src/main.rs b/src/main.rs
index d1df7fc..56b2dfa 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -182,7 +182,9 @@ static LONG_HELP: &str = "
 
     * cd [modulename]
       Changes your current working directory to the module
-      installation folder.
+      installation folder. When you don't provide a modulename
+      the working directory is changed to the module installation
+      folder of the last loaded module.
 
     * edit [modulename]
       Opens the modulefile in your $EDITOR or if this variable is not
@@ -412,12 +414,32 @@ fn run(args: &[String]) {
             }
         }
 
+        let loadedmodules: String;
         if num_hits != 1 {
             usage(true);
             return;
         } else {
             matches = true;
 
+            if command_hit == "cd" {
+                modulename = if modulename.is_empty() {
+                    match env::var(rsmod::ENV_LOADEDMODULES) {
+                        Ok(list) => loadedmodules = list,
+                        Err(_) => {
+                            loadedmodules = String::from("");
+                        }
+                    };
+
+                    let mut loadedmodules: Vec<&str> = loadedmodules.split(':').collect();
+                    loadedmodules.retain(|&x| x != "");
+
+                    let loadedmodule: &str = if !loadedmodules.is_empty() { loadedmodules[0] } else { "" };
+                    loadedmodule
+                } else {
+                    modulename
+                };
+            }
+
             if command_hit == "add" {
                 command_hit = "load";
             }
diff --git a/src/rsmodules.rs b/src/rsmodules.rs
index a386479..ce4cb3b 100644
--- a/src/rsmodules.rs
+++ b/src/rsmodules.rs
@@ -49,7 +49,7 @@ mod manage;
 mod script;
 
 static DEFAULT_MODULE_PATH: &str = "/usr/local";
-static ENV_LOADEDMODULES: &str = "LOADEDMODULES"; // name of an env var
+pub static ENV_LOADEDMODULES: &str = "LOADEDMODULES"; // name of an env var
 static ENV_UNDO: &str = "RSMODULES_UNDO"; // name of an env var
 
 #[derive(Debug, Default, Options)]
@@ -330,6 +330,10 @@ fn read_input<T: AsRef<str>>(filename: T) -> std::io::Result<(PathBuf, String)>
 }
 
 fn cd(selected_module: &str) -> Vec<String> {
+    if selected_module.is_empty() {
+        return Vec::new();
+    }
+
     let mut lines: Vec<String> = Vec::new();
     let paths = script::get_readme_paths();
 
@@ -513,7 +517,7 @@ fn module_action(rsmod: &mut Rsmodule, action: &str) {
 
     reversed_modules.reverse();
 
-    if rsmod.arg == "" {
+    if rsmod.cmd != "cd" && rsmod.arg == "" {
         // TODO: only print usage info about this subcommand
         super::usage(true);
         return;