From cedd28ded91fa4b0b786fd17e94954e6afb66646 Mon Sep 17 00:00:00 2001
From: Kai Harries <kai.harries@posteo.de>
Date: Fri, 1 Nov 2019 15:02:17 +0100
Subject: [PATCH 1/2] repl: support auto-completion when compiled with READLINE

---
 src/nix/repl.cc | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index f857b2e89c2..42839143b15 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -137,6 +137,30 @@ NixRepl::~NixRepl()
 
 static NixRepl * curRepl; // ugly
 
+#ifdef READLINE
+static char * completionFuncReadline(const char * text, int state)
+{
+    static StringSet matches = curRepl->completePrefix(text);
+
+    if (state == 0) {
+        matches = curRepl->completePrefix(text);
+    }
+
+    auto it = matches.begin();
+    while (state > 0 && it != matches.end()) {
+        it++;
+        state--;
+    }
+
+    if (it == matches.end()) {
+        return nullptr;
+    }
+    else {
+        return strdup(it->c_str());
+    }
+}
+
+#else
 static char * completionCallback(char * s, int *match) {
   auto possible = curRepl->completePrefix(s);
   if (possible.size() == 1) {
@@ -198,6 +222,7 @@ static int listPossibleCallback(char *s, char ***avp) {
 
   return ac;
 }
+#endif
 
 namespace {
     // Used to communicate to NixRepl::getLine whether a signal occurred in ::readline.
@@ -227,7 +252,9 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
 #endif
     read_history(historyFile.c_str());
     curRepl = this;
-#ifndef READLINE
+#ifdef READLINE
+    rl_completion_entry_function = completionFuncReadline;
+#else
     rl_set_complete_func(completionCallback);
     rl_set_list_possib_func(listPossibleCallback);
 #endif

From 40df2d424b493f654992ed3bf5fea8be66cca542 Mon Sep 17 00:00:00 2001
From: Kai Harries <kai.harries@posteo.de>
Date: Fri, 1 Nov 2019 22:06:40 +0100
Subject: [PATCH 2/2] repl: support history when compiled with READLINE

---
 src/nix/repl.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index 42839143b15..7fbd2524bd3 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -329,6 +329,11 @@ bool NixRepl::getLine(string & input, const std::string &prompt)
 
     if (!s)
       return false;
+#ifdef READLINE
+    if (*s) {
+        add_history(s);
+    }
+#endif
     input += s;
     input += '\n';
     return true;