refactor: Windows tilde expansion followup (#29380)

Followup to #28515:

Rename the static os_homedir() to os_uv_homedir() to emphasize that it
is a wrapper around a libuv function.

Add the function os_get_homedir() to os/env.c to return the cached
homedir value as a const. Must be called after homedir is initialized or
it fails.

The difference between this function and the static os_uv_homedir() is
that the latter gets the homedir from libuv and is used to initialize
homedir in init_homedir(), while os_get_homedir() just returns homedir
as a const if it's initialized and is public.

Use the os_get_homedir() accessor for ~/ expansion on Windows to make
the code more concise.

Add a Windows section to main_spec.lua with tests for expanding ~/ and
~\ prefixes for files passed in on the command-line.

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

1 files changed, 17 insertions, 6 deletions

diff --git a/src/nvim/os/env.c b/src/nvim/os/env.c
index 4689414559..a4d5c02b5b 100644
--- a/src/nvim/os/env.c
+++ b/src/nvim/os/env.c
@@ -400,17 +400,28 @@ void os_get_hostname(char *hostname, size_t size)
 ///   2. if $HOME is not set, try the following
 /// For Windows:
 ///   1. assemble homedir using HOMEDRIVE and HOMEPATH
-///   2. try os_homedir()
+///   2. try os_uv_homedir()
 ///   3. resolve a direct reference to another system variable
 ///   4. guess C drive
 /// For Unix:
-///   1. try os_homedir()
+///   1. try os_uv_homedir()
 ///   2. go to that directory
 ///     This also works with mounts and links.
 ///     Don't do this for Windows, it will change the "current dir" for a drive.
 ///   3. fall back to current working directory as a last resort
 static char *homedir = NULL;
-static char *os_homedir(void);
+static char *os_uv_homedir(void);
+
+/// Public accessor for the cached "real", resolved user home directory. See
+/// comment on `homedir`.
+const char *os_get_homedir(void)
+{
+  if (!homedir) {
+    emsg("os_get_homedir failed: homedir not initialized");
+    return NULL;
+  }
+  return homedir;
+}
 
 void init_homedir(void)
 {
@@ -440,7 +451,7 @@ void init_homedir(void)
     }
   }
   if (var == NULL) {
-    var = os_homedir();
+    var = os_uv_homedir();
   }
 
   // Weird but true: $HOME may contain an indirect reference to another
@@ -471,7 +482,7 @@ void init_homedir(void)
 
 #ifdef UNIX
   if (var == NULL) {
-    var = os_homedir();
+    var = os_uv_homedir();
   }
 
   // Get the actual path.  This resolves links.
@@ -492,7 +503,7 @@ void init_homedir(void)
 
 static char homedir_buf[MAXPATHL];
 
-static char *os_homedir(void)
+static char *os_uv_homedir(void)
 {
   homedir_buf[0] = NUL;
   size_t homedir_size = MAXPATHL;