From 42645063302e328e26360cb08baceb5107fbfa8c Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 3 Mar 2025 13:10:08 +0100
Subject: [PATCH] Imply --offline during tab completion

Previously, if you don't have Internet connectivity, tab completion
might try to fetch the flake registry, e.g.

  $ NIX_GET_COMPLETIONS=4 nix build -vvvvv --offline /home/eelco/De
  evaluating file '<nix/derivation-internal.nix>'
  downloading 'https://channels.nixos.org/flake-registry.json'...
  warning: error: unable to download 'https://channels.nixos.org/flake-registry.json': Could not resolve hostname (6) Could not resolve host: channels.nixos.org; retrying in 294 ms
  warning: error: unable to download 'https://channels.nixos.org/flake-registry.json': Could not resolve hostname (6) Could not resolve host: channels.nixos.org; retrying in 541 ms
  warning: error: unable to download 'https://channels.nixos.org/flake-registry.json': Could not resolve hostname (6) Could not resolve host: channels.nixos.org; retrying in 1230 ms
  warning: error: unable to download 'https://channels.nixos.org/flake-registry.json': Could not resolve hostname (6) Could not resolve host: channels.nixos.org; retrying in 2285 ms
  warning: error: unable to download 'https://channels.nixos.org/flake-registry.json': Could not resolve hostname (6) Could not resolve host: channels.nixos.org; using cached version
---
 src/nix/main.cc | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/src/nix/main.cc b/src/nix/main.cc
index 74d22e4336..b75e49cc3d 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -86,6 +86,19 @@ static bool haveInternet()
 #endif
 }

+static void disableNet()
+{
+    // FIXME: should check for command line overrides only.
+    if (!settings.useSubstitutes.overridden)
+        settings.useSubstitutes = false;
+    if (!settings.tarballTtl.overridden)
+        settings.tarballTtl = std::numeric_limits<unsigned int>::max();
+    if (!fileTransferSettings.tries.overridden)
+        fileTransferSettings.tries = 0;
+    if (!fileTransferSettings.connectTimeout.overridden)
+        fileTransferSettings.connectTimeout = 1;
+}
+
 std::string programPath;

 struct NixArgs : virtual MultiCommand, virtual MixCommonArgs, virtual RootArgs
@@ -482,6 +495,12 @@ void mainWrapped(int argc, char ** argv)
         }
     });

+    if (getEnv("NIX_GET_COMPLETIONS"))
+        /* Avoid fetching stuff during tab completion. We have to this
+           early because we haven't checked `haveInternet()` yet
+           (below). */
+        disableNet();
+
     try {
         auto isNixCommand = std::regex_search(programName, std::regex("nix$"));
         auto allowShebang = isNixCommand && argc > 1;
@@ -525,17 +544,8 @@ void mainWrapped(int argc, char ** argv)
         args.useNet = false;
     }

-    if (!args.useNet) {
-        // FIXME: should check for command line overrides only.
-        if (!settings.useSubstitutes.overridden)
-            settings.useSubstitutes = false;
-        if (!settings.tarballTtl.overridden)
-            settings.tarballTtl = std::numeric_limits<unsigned int>::max();
-        if (!fileTransferSettings.tries.overridden)
-            fileTransferSettings.tries = 0;
-        if (!fileTransferSettings.connectTimeout.overridden)
-            fileTransferSettings.connectTimeout = 1;
-    }
+    if (!args.useNet)
+        disableNet();

     if (args.refresh) {
         settings.tarballTtl = 0;
--
2.50.1

Sergei Zimmerman (xokdvium) I'm trying to move the data into arena, and something appears to be leaking. Any idea why? The assignment operator should clean up the existing value, right?

        attrs = AttrDefs{std::move(attrs), arena};
        if (inheritFromExprs)
            inheritFromExprs = std::make_unique<std::pmr::vector<Expr *>>(std::move(*inheritFromExprs), arena);
        dynamicAttrs = DynamicAttrDefs{std::move(dynamicAttrs), arena};

std::map move constructor (AttrDefs is std::map):

      /// Allocator-extended move constructor.
      map(map&& __m, const __type_identity_t<allocator_type>& __a)
      noexcept(is_nothrow_copy_constructible<_Compare>::value
	       && _Alloc_traits::_S_always_equal())
      : _M_t(std::move(__m._M_t), _Pair_alloc_type(__a)) { }