From a5f6ee8550b78badffe48993b0a236b7934c1be5 Mon Sep 17 00:00:00 2001
From: shivaraj-bh <sbh69840@gmail.com>
Date: Wed, 14 Aug 2024 14:57:34 +0530
Subject: [PATCH] `nix flake show`: Support `meta` attribute for `apps`

Metadata information for flake apps will be useful while exploring a
flake using `nix flake show`
---
 src/nix/flake.cc | 12 +++++++++---
 src/nix/run.md   |  3 +++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 3f9f8f99b..09f41dca8 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -1251,8 +1251,7 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                         }
                         j.emplace("type", "derivation");
                         j.emplace("name", name);
-                        if (description)
-                            j.emplace("description", *description);
+                        j.emplace("description", description ? *description : "");
                     } else {
                         logger->cout("%s: %s '%s'",
                             headerPrefix,
@@ -1340,12 +1339,19 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                     (attrPath.size() == 3 && attrPathS[0] == "apps"))
                 {
                     auto aType = visitor.maybeGetAttr("type");
+                    std::optional<std::string> description;
+                    if (auto aMeta = visitor.maybeGetAttr(state->sMeta)) {
+                        if (auto aDescription = aMeta->maybeGetAttr(state->sDescription))
+                            description = aDescription->getString();
+                    }
                     if (!aType || aType->getString() != "app")
                         state->error<EvalError>("not an app definition").debugThrow();
                     if (json) {
                         j.emplace("type", "app");
+                        if (description)
+                            j.emplace("description", *description);
                     } else {
-                        logger->cout("%s: app", headerPrefix);
+                        logger->cout("%s: app: " ANSI_BOLD "%s" ANSI_NORMAL, headerPrefix, description ? *description : "no description");
                     }
                 }
 
diff --git a/src/nix/run.md b/src/nix/run.md
index 250ea65aa..eb96e6b31 100644
--- a/src/nix/run.md
+++ b/src/nix/run.md
@@ -80,6 +80,7 @@ An app is specified by a flake output attribute named
 apps.x86_64-linux.blender_2_79 = {
   type = "app";
   program = "${self.packages.x86_64-linux.blender_2_79}/bin/blender";
+  meta.description = "Run Blender, a free and open-source 3D creation suite.";
 };
 ```
 
@@ -90,4 +91,6 @@ The only supported attributes are:
 * `program` (required): The full path of the executable to run. It
   must reside in the Nix store.
 
+* `meta.description` (optional): A description of the app.
+
 )""