From 9ff1a9ea65bdeb520becb843b8300a23fb88a5a9 Mon Sep 17 00:00:00 2001
From: Nick Van den Broeck <nick.van.den.broeck666@gmail.com>
Date: Wed, 27 Feb 2019 19:54:18 +0100
Subject: [PATCH] Implemented json flag for `nix flake info`

---
 src/libexpr/primops/flake.cc |  2 +-
 src/libexpr/primops/flake.hh |  2 +-
 src/nix/command.cc           |  9 +++++++++
 src/nix/command.hh           |  7 +++++++
 src/nix/flake.cc             | 14 +++++++++++---
 5 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/src/libexpr/primops/flake.cc b/src/libexpr/primops/flake.cc
index 9f137a0b9..ac0421549 100644
--- a/src/libexpr/primops/flake.cc
+++ b/src/libexpr/primops/flake.cc
@@ -141,7 +141,7 @@ static FlakeSourceInfo fetchFlake(EvalState & state, const FlakeRef & flakeRef)
     else abort();
 }
 
-static Flake getFlake(EvalState & state, const FlakeRef & flakeRef)
+Flake getFlake(EvalState & state, const FlakeRef & flakeRef)
 {
     auto sourceInfo = fetchFlake(state, flakeRef);
     debug("got flake source '%s' with revision %s",
diff --git a/src/libexpr/primops/flake.hh b/src/libexpr/primops/flake.hh
index af28bc5b0..194b969a2 100644
--- a/src/libexpr/primops/flake.hh
+++ b/src/libexpr/primops/flake.hh
@@ -34,5 +34,5 @@ struct Flake
     // content hash
 };
 
-static Flake getFlake(EvalState & state, const FlakeRef & flakeRef);
+Flake getFlake(EvalState & state, const FlakeRef & flakeRef);
 }
diff --git a/src/nix/command.cc b/src/nix/command.cc
index 5967ab36c..e1e32aaae 100644
--- a/src/nix/command.cc
+++ b/src/nix/command.cc
@@ -27,6 +27,15 @@ void StoreCommand::run()
     run(getStore());
 }
 
+JsonFormattable::JsonFormattable()
+{
+    mkFlag()
+        .longName("json-formattable")
+        .shortName('j')
+        .description("output will be printed as json")
+        .handler([&]() { jsonFormatting = true; });
+}
+
 StorePathsCommand::StorePathsCommand(bool recursive)
     : recursive(recursive)
 {
diff --git a/src/nix/command.hh b/src/nix/command.hh
index b3248222e..5c2f8c304 100644
--- a/src/nix/command.hh
+++ b/src/nix/command.hh
@@ -26,6 +26,13 @@ private:
     std::shared_ptr<Store> _store;
 };
 
+struct JsonFormattable : virtual Command
+{
+    bool jsonFormatting = false;;
+
+    JsonFormattable();
+};
+
 struct Buildable
 {
     Path drvPath; // may be empty
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 099425688..22e5b297c 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -4,6 +4,7 @@
 #include "shared.hh"
 #include "progress-bar.hh"
 #include "eval.hh"
+#include <nlohmann/json.hpp>
 
 using namespace nix;
 
@@ -33,7 +34,7 @@ struct CmdFlakeList : StoreCommand, MixEvalArgs
     }
 };
 
-struct CmdFlakeInfo : FlakeCommand
+struct CmdFlakeInfo : FlakeCommand, JsonFormattable
 {
     std::string name() override
     {
@@ -49,8 +50,15 @@ struct CmdFlakeInfo : FlakeCommand
     {
         auto evalState = std::make_shared<EvalState>(searchPath, store);
         nix::Flake flake = nix::getFlake(*evalState, FlakeRef(flakeUri));
-        std::cout << "Location:    " << flake.path << "\n";
-        std::cout << "Description: " << flake.description << "\n";
+        if (jsonFormatting) {
+            nlohmann::json j;
+            j["location"] = flake.path;
+            j["description"] = flake.description;
+            std::cout << j.dump(4) << std::endl;
+        } else {
+            std::cout << "Location:    " << flake.path << "\n";
+            std::cout << "Description: " << flake.description << "\n";
+        }
     }
 };