From 2998527b185a41157be6ead42fd03a66601c4f56 Mon Sep 17 00:00:00 2001
From: Jimmy Reichley <jimmyqpublik@gmail.com>
Date: Tue, 10 May 2022 16:53:22 -0400
Subject: [PATCH 1/2] Allow setting bash-prompt-prefix nix develop
 configuration

---
 src/libexpr/flake/config.cc | 2 +-
 src/nix/develop.cc          | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/libexpr/flake/config.cc b/src/libexpr/flake/config.cc
index 92ec27046..3e9d264b4 100644
--- a/src/libexpr/flake/config.cc
+++ b/src/libexpr/flake/config.cc
@@ -31,7 +31,7 @@ static void writeTrustedList(const TrustedList & trustedList)
 
 void ConfigFile::apply()
 {
-    std::set<std::string> whitelist{"bash-prompt", "bash-prompt-suffix", "flake-registry"};
+    std::set<std::string> whitelist{"bash-prompt", "bash-prompt-prefix", "bash-prompt-suffix", "flake-registry"};
 
     for (auto & [name, value] : settings) {
 
diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index 3a99fff6f..2a3fc0213 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -18,6 +18,9 @@ struct DevelopSettings : Config
     Setting<std::string> bashPrompt{this, "", "bash-prompt",
         "The bash prompt (`PS1`) in `nix develop` shells."};
 
+    Setting<std::string> bashPromptPrefix{this, "", "bash-prompt-prefix",
+        "Prefix prepended to the `PS1` environment variable in `nix develop` shells."};
+
     Setting<std::string> bashPromptSuffix{this, "", "bash-prompt-suffix",
         "Suffix appended to the `PS1` environment variable in `nix develop` shells."};
 };
@@ -482,6 +485,9 @@ struct CmdDevelop : Common, MixEnvironment
             if (developSettings.bashPrompt != "")
                 script += fmt("[ -n \"$PS1\" ] && PS1=%s;\n",
                     shellEscape(developSettings.bashPrompt.get()));
+            if (developSettings.bashPromptPrefix != "")
+                script += fmt("[ -n \"$PS1\" ] && PS1=%s\"$PS1\";\n",
+                    shellEscape(developSettings.bashPromptPrefix.get()));
             if (developSettings.bashPromptSuffix != "")
                 script += fmt("[ -n \"$PS1\" ] && PS1+=%s;\n",
                     shellEscape(developSettings.bashPromptSuffix.get()));

From 584475acf9f4b8eda2a451901f6f9af35ae976e0 Mon Sep 17 00:00:00 2001
From: Jimmy Reichley <jimmyqpublik@gmail.com>
Date: Tue, 10 May 2022 16:55:25 -0400
Subject: [PATCH 2/2] Add documentation for bash-prompt-prefix

---
 src/nix/develop.md | 4 ++--
 src/nix/flake.md   | 7 ++++---
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/nix/develop.md b/src/nix/develop.md
index 8bcff66c9..e036ec6b9 100644
--- a/src/nix/develop.md
+++ b/src/nix/develop.md
@@ -80,8 +80,8 @@ initialised by `stdenv` and exits. This build environment can be
 recorded into a profile using `--profile`.
 
 The prompt used by the `bash` shell can be customised by setting the
-`bash-prompt` and `bash-prompt-suffix` settings in `nix.conf` or in
-the flake's `nixConfig` attribute.
+`bash-prompt`, `bash-prompt-prefix`, and `bash-prompt-suffix` settings in
+`nix.conf` or in the flake's `nixConfig` attribute.
 
 # Flake output attributes
 
diff --git a/src/nix/flake.md b/src/nix/flake.md
index c8251eb74..aa3f9f303 100644
--- a/src/nix/flake.md
+++ b/src/nix/flake.md
@@ -331,9 +331,10 @@ The following attributes are supported in `flake.nix`:
 
 * `nixConfig`: a set of `nix.conf` options to be set when evaluating any
   part of a flake. In the interests of security, only a small set of
-  whitelisted options (currently `bash-prompt`, `bash-prompt-suffix`,
-  and `flake-registry`) are allowed to be set without confirmation so long as
-  `accept-flake-config` is not set in the global configuration.
+  whitelisted options (currently `bash-prompt`, `bash-prompt-prefix`,
+  `bash-prompt-suffix`, and `flake-registry`) are allowed to be set without
+  confirmation so long as `accept-flake-config` is not set in the global
+  configuration.
 
 ## Flake inputs