From 0056a5aea1a7b68bdacb7b829c325a1d4a3c4259 Mon Sep 17 00:00:00 2001
From: Maximilian Bosch <maximilian@mbosch.me>
Date: Fri, 21 Feb 2020 19:11:58 +0100
Subject: [PATCH] debug: add module

This one is fairly similar to `environment.enableDebugInfo`[1] (hence
the name). It ensures that the `debug`-output of packages defined in
`home.packages` is installed if available and ensures that
`gdb`/`elfutils` find those symbols by adding
`~/.nix-profile/lib/debug` to the `NIX_DEBUG_INFO_DIRS`[2] variable.

[1] https://github.com/NixOS/nixpkgs/blob/release-19.09/nixos/modules/config/debug-info.nix
[2] https://github.com/NixOS/nixpkgs/blob/release-19.09/pkgs/development/tools/misc/gdb/debug-info-from-env.patch

PR #1040
---
 modules/misc/debug.nix               | 26 ++++++++++++++++++++++++++
 modules/modules.nix                  |  1 +
 tests/default.nix                    |  3 ++-
 tests/modules/misc/debug/default.nix | 25 +++++++++++++++++++++++++
 4 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100644 modules/misc/debug.nix
 create mode 100644 tests/modules/misc/debug/default.nix

diff --git a/modules/misc/debug.nix b/modules/misc/debug.nix
new file mode 100644
index 000000000..d27d496b4
--- /dev/null
+++ b/modules/misc/debug.nix
@@ -0,0 +1,26 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+{
+  options.home = {
+    enableDebugInfo = mkEnableOption "" // {
+      description = ''
+        Some Nix-packages provide debug symbols for
+        <command>gdb</command> in the <literal>debug</literal>-output.
+        This option ensures that those are automatically fetched from
+        the binary cache if available and <command>gdb</command> is
+        configured to find those symbols.
+      '';
+    };
+  };
+
+  config = mkIf config.home.enableDebugInfo {
+    home.extraOutputsToInstall = [ "debug" ];
+
+    home.sessionVariables = {
+      NIX_DEBUG_INFO_DIRS =
+        "$NIX_DEBUG_INFO_DIRS\${NIX_DEBUG_INFO_DIRS:+:}${config.home.profileDirectory}/lib/debug";
+    };
+  };
+}
diff --git a/modules/modules.nix b/modules/modules.nix
index 263c1176c..83d5a4dd5 100644
--- a/modules/modules.nix
+++ b/modules/modules.nix
@@ -26,6 +26,7 @@ let
     (loadModule ./home-environment.nix { })
     (loadModule ./manual.nix { })
     (loadModule ./misc/dconf.nix { })
+    (loadModule ./misc/debug.nix { })
     (loadModule ./misc/fontconfig.nix { })
     (loadModule ./misc/gtk.nix { })
     (loadModule ./misc/lib.nix { })
diff --git a/tests/default.nix b/tests/default.nix
index 11e9b7d2f..5a342625a 100644
--- a/tests/default.nix
+++ b/tests/default.nix
@@ -43,10 +43,11 @@ import nmt {
     ./modules/programs/zsh
     ./modules/xresources
   ] ++ lib.optionals pkgs.stdenv.hostPlatform.isLinux [
-    ./modules/programs/abook
+    ./modules/misc/debug
     ./modules/misc/pam
     ./modules/misc/xdg
     ./modules/misc/xsession
+    ./modules/programs/abook
     ./modules/programs/firefox
     ./modules/programs/getmail
     ./modules/programs/rofi
diff --git a/tests/modules/misc/debug/default.nix b/tests/modules/misc/debug/default.nix
new file mode 100644
index 000000000..b42462d08
--- /dev/null
+++ b/tests/modules/misc/debug/default.nix
@@ -0,0 +1,25 @@
+{
+  debug = { pkgs, config, lib, ... }: {
+    home.enableDebugInfo = true;
+    home.packages = with pkgs; [ curl gdb ];
+
+    nmt.script = ''
+      [ -L $TESTED/home-path/lib/debug/curl ] \
+        || fail "Debug-symbols for pkgs.curl should exist in \`/home-path/lib/debug'!"
+
+      #source $TESTED/home-path/etc/profile.d/hm-session-vars.sh
+      #[[ "$NIX_DEBUG_INFO_DIRS" =~ /lib/debug$ ]] \
+        #|| fail "Invalid NIX_DEBUG_INFO_DIRS!"
+      assertFileExists home-path/etc/profile.d/hm-session-vars.sh
+      assertFileRegex home-path/etc/profile.d/hm-session-vars.sh \
+          'NIX_DEBUG_INFO_DIRS=.*/lib/debug'
+
+      # We need to override NIX_DEBUG_INFO_DIRS here as $HOME evalutes to the home
+      # of the user who executes this testcase :/
+      { echo quit | PATH="$TESTED/home-path/bin''${PATH:+:}$PATH" NIX_DEBUG_INFO_DIRS=$TESTED/home-path/lib/debug \
+        gdb curl 2>&1 | \
+        grep 'Reading symbols from ${builtins.storeDir}/'; \
+      } || fail "Failed to read debug symbols from curl in gdb"
+    '';
+  };
+}