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