fix: always search ~/.terminfo for terminfo files (#122)

Per the manual:

1. Search TERMINFO.
2. Search ~/.terminfo.
3. Search TERMINFO_DIRS.
4. Search /usr/share/terminfo and friends.

Technically we're allowed to omit the search in ~/.terminfo entirely,
but this would introduce surprising results and we should just do what
ncurses does.

fixes #121

src/terminfo/searcher.rs

@@ -16,61 +16,67 @@ use std::env;
 use std::fs;
 use std::path::PathBuf;
 
+// The default terminfo location should be /usr/lib/terminfo but that's not guaranteed, so we check
+// a few more locations. See https://tldp.org/HOWTO/Text-Terminal-HOWTO-16.html#ss16.2
+const DEFAULT_LOCATIONS: &[&str] = &[
+    "/etc/terminfo",
+    "/usr/share/terminfo",
+    "/usr/lib/terminfo",
+    "/lib/terminfo",
+    #[cfg(target_os = "haiku")]
+    "/boot/system/data/terminfo",
+];
+
 /// Return path to database entry for `term`
 pub fn get_dbpath_for_term(term: &str) -> Option<PathBuf> {
     let mut dirs_to_search = Vec::new();
+    let mut default_locations = DEFAULT_LOCATIONS.iter().map(PathBuf::from);
     let first_char = match term.chars().next() {
         Some(c) => c,
         None => return None,
     };
 
-    // Find search directory
-    // The terminfo manual says:
-    //
-    // > If  the  environment  variable  TERMINFO is set, it is interpreted
-    // > as the pathname of a directory containing the compiled description
-    // > you are working on.  Only that directory is searched.
-    //
-    // However, the ncurses manual says:
+    // From the manual.
     //
-    // > If the environment variable TERMINFO is defined, any program using
-    // > curses checks for a local terminal definition  before  checking in
-    // > the standard place.
-    //
-    // Given that ncurses is the defacto standard, we follow the ncurses manual.
+    // > The  environment  variable TERMINFO is checked first, for a terminal
+    // > database containing the terminal description.
     if let Some(dir) = env::var_os("TERMINFO") {
         dirs_to_search.push(PathBuf::from(dir));
     }
 
+    // > Next, ncurses looks in $HOME/.terminfo for a compiled description.
+    if let Some(mut homedir) = home::home_dir() {
+        homedir.push(".terminfo");
+        dirs_to_search.push(homedir)
+    }
+
+    // > Next, if the environment variable TERMINFO_DIRS is set, ncurses interprets
+    // > the contents of that variable as a list of colon-separated pathnames of
+    // > terminal databases to be searched.
+    // >
+    // > An  empty  pathname  (i.e.,  if  the  variable begins or ends with a
+    // > colon, or contains adjacent colons) is interpreted as the system location
+    // > /usr/share/terminfo.
     if let Ok(dirs) = env::var("TERMINFO_DIRS") {
         for i in dirs.split(':') {
             if i.is_empty() {
-                dirs_to_search.push(PathBuf::from("/usr/share/terminfo"));
+                dirs_to_search.extend(&mut default_locations);
             } else {
                 dirs_to_search.push(PathBuf::from(i));
             }
         }
-    } else {
-        // Found nothing in TERMINFO_DIRS, use the default paths:
-        // According to  /etc/terminfo/README, after looking at
-        // ~/.terminfo, ncurses will search /etc/terminfo, then
-        // /lib/terminfo, and eventually /usr/share/terminfo.
-        // On Haiku the database can be found at /boot/system/data/terminfo
-        if let Some(mut homedir) = home::home_dir() {
-            homedir.push(".terminfo");
-            dirs_to_search.push(homedir)
-        }
-
-        dirs_to_search.push(PathBuf::from("/etc/terminfo"));
-        dirs_to_search.push(PathBuf::from("/lib/terminfo"));
-        dirs_to_search.push(PathBuf::from("/usr/share/terminfo"));
-        dirs_to_search.push(PathBuf::from("/boot/system/data/terminfo"));
     }
 
+    // > Finally, ncurses searches these compiled-in locations...
+    //
+    // NOTE: We only append these to `dirs_to_search` once. If we've already added these
+    // directories as specified in `TERMINFO_DIRS`, this operation will be a no-op.
+    dirs_to_search.extend(&mut default_locations);
+
     // Look for the terminal in all of the search directories
     for mut p in dirs_to_search {
         if fs::metadata(&p).is_ok() {
-            p.push(&first_char.to_string());
+            p.push(first_char.to_string());
             p.push(term);
             if fs::metadata(&p).is_ok() {
                 return Some(p);
@@ -80,7 +86,7 @@ pub fn get_dbpath_for_term(term: &str) -> Option<PathBuf> {
 
             // on some installations the dir is named after the hex of the char
             // (e.g. OS X)
-            p.push(&format!("{:x}", first_char as usize));
+            p.push(format!("{:x}", first_char as usize));
             p.push(term);
             if fs::metadata(&p).is_ok() {
                 return Some(p);