From d69a1117a4bf44da9ad2f0f0788433a149889fb3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Na=C3=AFm=20Favier?= <n@monade.li>
Date: Sat, 19 Feb 2022 14:26:34 +0100
Subject: [PATCH] Perform tilde expansion when completing flake fragments

Allows completing `nix build ~/flake#<Tab>`.
We can implement expansion for `~user` later if needed.
Not using wordexp(3) since that expands way too much.
---
 misc/bash/completion.sh    |  2 +-
 src/libcmd/installables.cc |  4 ++--
 src/libutil/args.cc        |  7 ++++---
 src/libutil/util.cc        | 11 +++++++++++
 src/libutil/util.hh        |  3 +++
 5 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/misc/bash/completion.sh b/misc/bash/completion.sh
index 045053dee..9af695f5a 100644
--- a/misc/bash/completion.sh
+++ b/misc/bash/completion.sh
@@ -15,7 +15,7 @@ function _complete_nix {
         else
             COMPREPLY+=("$completion")
         fi
-    done < <(NIX_GET_COMPLETIONS=$cword "${words[@]/#\~/$HOME}" 2>/dev/null)
+    done < <(NIX_GET_COMPLETIONS=$cword "${words[@]}" 2>/dev/null)
     __ltrim_colon_completions "$cur"
 }
 
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 5acb0ef11..38d430132 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -1,4 +1,5 @@
 #include "installables.hh"
+#include "util.hh"
 #include "command.hh"
 #include "attr-path.hh"
 #include "common-eval-args.hh"
@@ -253,8 +254,7 @@ void completeFlakeRefWithFragment(
 
             auto fragment = prefix.substr(hash + 1);
             auto flakeRefS = std::string(prefix.substr(0, hash));
-            // FIXME: do tilde expansion.
-            auto flakeRef = parseFlakeRef(flakeRefS, absPath("."));
+            auto flakeRef = parseFlakeRef(expandTilde(flakeRefS), absPath("."));
 
             auto evalCache = openEvalCache(*evalState,
                 std::make_shared<flake::LockedFlake>(lockFlake(*evalState, flakeRef, lockFlags)));
diff --git a/src/libutil/args.cc b/src/libutil/args.cc
index db0f73cbf..27dca48a1 100644
--- a/src/libutil/args.cc
+++ b/src/libutil/args.cc
@@ -282,12 +282,13 @@ static void _completePath(std::string_view prefix, bool onlyDirs)
 {
     completionType = ctFilenames;
     glob_t globbuf;
-    int flags = GLOB_NOESCAPE | GLOB_TILDE;
+    int flags = GLOB_NOESCAPE;
     #ifdef GLOB_ONLYDIR
     if (onlyDirs)
         flags |= GLOB_ONLYDIR;
     #endif
-    if (glob((std::string(prefix) + "*").c_str(), flags, nullptr, &globbuf) == 0) {
+    // using expandTilde here instead of GLOB_TILDE(_CHECK) so that ~<Tab> expands to /home/user/
+    if (glob((expandTilde(prefix) + "*").c_str(), flags, nullptr, &globbuf) == 0) {
         for (size_t i = 0; i < globbuf.gl_pathc; ++i) {
             if (onlyDirs) {
                 auto st = stat(globbuf.gl_pathv[i]);
@@ -295,8 +296,8 @@ static void _completePath(std::string_view prefix, bool onlyDirs)
             }
             completions->add(globbuf.gl_pathv[i]);
         }
-        globfree(&globbuf);
     }
+    globfree(&globbuf);
 }
 
 void completePath(size_t, std::string_view prefix)
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index f9da86d8d..b0fe97e4e 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -200,6 +200,17 @@ std::string_view baseNameOf(std::string_view path)
 }
 
 
+std::string expandTilde(std::string_view path)
+{
+    // TODO: expand ~user ?
+    auto tilde = path.substr(0, 2);
+    if (tilde == "~/" || tilde == "~")
+        return getHome() + std::string(path.substr(1));
+    else
+        return std::string(path);
+}
+
+
 bool isInDir(std::string_view path, std::string_view dir)
 {
     return path.substr(0, 1) == "/"
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 970a5d13c..9ed72e718 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -68,6 +68,9 @@ Path dirOf(const PathView path);
    following the final `/' (trailing slashes are removed). */
 std::string_view baseNameOf(std::string_view path);
 
+/* Perform tilde expansion on a path. */
+std::string expandTilde(std::string_view path);
+
 /* Check whether 'path' is a descendant of 'dir'. Both paths must be
    canonicalized. */
 bool isInDir(std::string_view path, std::string_view dir);