From cb84f77f1d845a986369b62d561be24a85a5b165 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Thu, 6 Jun 2024 19:08:07 +0200
Subject: [PATCH 01/13] Make the toplevel interface a module

---
 lib/lib.nix          |   8 ++--
 lib/modules/main.ncl |  44 +++++++++++++++++++
 lib/organist.ncl     |   1 +
 lib/schema.ncl       |   2 +-
 project.ncl          | 102 ++++++++++++++++++++++---------------------
 5 files changed, 104 insertions(+), 53 deletions(-)
 create mode 100644 lib/modules/main.ncl

diff --git a/lib/lib.nix b/lib/lib.nix
index 6dba8f0d..6abbea84 100644
--- a/lib/lib.nix
+++ b/lib/lib.nix
@@ -11,8 +11,6 @@
   # Export a Nix value to be consumed by Nickel
   typeField = "$__organist_type";
 
-  isInStore = lib.hasPrefix builtins.storeDir;
-
   # Take a symbolic derivation (a datastructure representing a derivation), as
   # produced by Nickel, and transform it into valid arguments to
   # `derivation`
@@ -87,7 +85,11 @@
         let
           organistType = value."${typeField}" or "";
         in
-          if isNickelDerivation organistType
+          if organistType == "module"
+          then
+            assert value ? config;
+              importFromNickel_ value.config
+          else if isNickelDerivation organistType
           then let
             prepared = prepareDerivation system (builtins.mapAttrs (_:
               importFromNickel_)
diff --git a/lib/modules/main.ncl b/lib/modules/main.ncl
new file mode 100644
index 00000000..3223cb4d
--- /dev/null
+++ b/lib/modules/main.ncl
@@ -0,0 +1,44 @@
+# A library defining some kind of module system for Nickel
+{
+  T
+    | doc m%"
+      The type of a module.
+    "%
+    = {
+      config | Schema = {},
+      Schema
+        | not_exported
+        = {},
+      "$__organist_type" | force = "module",
+    },
+
+  submodules
+    | { _ : T } -> T
+    | doc m%"
+      Joins all the given module into a single one, prefixing all the keys of
+      their options with the key of the corresponding module.
+
+      ```nickel
+      submodules {
+          mod1 = { Schema.foo | Number, config.foo = 1 },
+          mod2 = { Schema.foo | String, config.foo = "bar" },
+        }
+
+        => {
+          Schema = { mod1.foo | Number, mod2.foo | String },
+          config = { mod1.foo = 1, mod2.bar = "bar" }
+        }
+      ```
+    "%
+    = fun modules =>
+      let configs = modules |> std.record.map (fun k v => v.config) in
+      let schemas = modules |> std.record.map (fun k v => v.Schema) in
+      {
+        Schema = schemas,
+        config | Schema = configs,
+      } | T,
+
+  merge2
+    | T -> T -> T
+    = fun m1 m2 => m1 & m2,
+}
diff --git a/lib/organist.ncl b/lib/organist.ncl
index ef6d7096..d9f2e1db 100644
--- a/lib/organist.ncl
+++ b/lib/organist.ncl
@@ -1,5 +1,6 @@
 {
   nix = import "./nix-interop/nix.ncl",
+  modules = import "./modules/main.ncl",
   shells = nix.shells,
   schema = import "./schema.ncl",
   OrganistExpression = schema.OrganistExpression,
diff --git a/lib/schema.ncl b/lib/schema.ncl
index b293f6ce..d8358c75 100644
--- a/lib/schema.ncl
+++ b/lib/schema.ncl
@@ -47,7 +47,7 @@ let filegen = import "files.ncl" in
   #
   # The contract must be: what the Nix side of the code can "parse" without
   # erroring out.
-  OrganistExpression =
+  OrganistExpression.Schema =
     {
       shells
         | doc m%"
diff --git a/project.ncl b/project.ncl
index 39fc528c..1ba551e4 100644
--- a/project.ncl
+++ b/project.ncl
@@ -2,56 +2,60 @@ let inputs = import "./nickel.lock.ncl" in
 let organist = inputs.organist in
 let import_nix = organist.nix.import_nix in
 
-{
-  shells =
-    organist.shells.Bash
-    & {
-      build.packages = {
-        nickel = import_nix "nixpkgs#nickel",
-        parallel = import_nix "nixpkgs#parallel",
-        gnused = import_nix "nixpkgs#gnused",
-      },
-    },
+organist.OrganistExpression
+& {
+  Schema,
+  config | Schema = {
 
-  flake.apps.run-test =
-    let testScript | organist.nix.builders.ShellApplication = {
-        name = "run-test.sh",
-        content.file = organist.nix.builtins.import_file "run-test.sh",
-        runtime_inputs = {
-          nickel = import_nix "nixpkgs#nickel",
-          parallel = import_nix "nixpkgs#parallel",
-          gnused = import_nix "nixpkgs#gnused",
+      shells =
+        organist.shells.Bash
+        & {
+          build.packages = {
+            nickel = import_nix "nixpkgs#nickel",
+            parallel = import_nix "nixpkgs#parallel",
+            gnused = import_nix "nixpkgs#gnused",
+          },
         },
-      }
-      in
-    {
-      type = "app",
-      program | organist.nix.derivation.NixString = nix-s%"%{testScript}/bin/run-test.sh"%
-    },
 
-  flake.packages = {
-    # Re-exported to make it easy for downstream to depend on them
-    nickel = import_nix "nixpkgs#nickel",
-    nls = import_nix "nixpkgs#nls",
-  },
+      flake.apps.run-test =
+        let testScript | organist.nix.builders.ShellApplication = {
+            name = "run-test.sh",
+            content.file = organist.nix.builtins.import_file "run-test.sh",
+            runtime_inputs = {
+              nickel = import_nix "nixpkgs#nickel",
+              parallel = import_nix "nixpkgs#parallel",
+              gnused = import_nix "nixpkgs#gnused",
+            },
+          }
+          in
+        {
+          type = "app",
+          program | organist.nix.derivation.NixString = nix-s%"%{testScript}/bin/run-test.sh"%
+        },
 
-  flake.checks
-    | { _ | organist.nix.builders.NixpkgsPkg }
-    = {
-      alejandra = {
-        name = "check-alejandra",
-        version = "0.0",
-        env.buildCommand = nix-s%"
+      flake.packages = {
+        # Re-exported to make it easy for downstream to depend on them
+        nickel = import_nix "nixpkgs#nickel",
+        nls = import_nix "nixpkgs#nls",
+      },
+
+      flake.checks
+        | { _ | organist.nix.builders.NixpkgsPkg }
+        = {
+          alejandra = {
+            name = "check-alejandra",
+            version = "0.0",
+            env.buildCommand = nix-s%"
           %{import_nix "nixpkgs#alejandra"}/bin/alejandra --check %{import_nix "self"}
           touch $out
         "%,
-      },
+          },
 
-      nickel-format = {
-        name = "check-nickel-format",
-        version = "0.0",
-        env.buildInputs.nickel = import_nix "nixpkgs#nickel",
-        env.buildCommand = nix-s%"
+          nickel-format = {
+            name = "check-nickel-format",
+            version = "0.0",
+            env.buildInputs.nickel = import_nix "nixpkgs#nickel",
+            env.buildCommand = nix-s%"
           cd %{import_nix "self"}
           failed=""
           for f in $(find . -name future -prune -or -name '*.ncl' -print); do
@@ -65,17 +69,17 @@ let import_nix = organist.nix.import_nix in
           fi
           touch $out
         "%,
-      },
-    },
+          },
+        },
 
-  flake.checks = import "tests/main.ncl",
+      flake.checks = import "tests/main.ncl",
 
-  files.".gitignore".materialisation_method = 'Copy,
-  files.".gitignore".content = m%"
+      files.".gitignore".materialisation_method = 'Copy,
+      files.".gitignore".content = m%"
     # This file is generated by Organist, please don't edit directly
     /examples/*/result
     /result
 
   "%,
-}
-  | organist.OrganistExpression
+    },
+} | organist.modules.T

From da8747265d4d025cd7ca394d03be15f235264c70 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Thu, 6 Jun 2024 19:17:33 +0200
Subject: [PATCH 02/13] Use a module for the files generation

---
 lib/files.ncl  | 134 ++++++++++++++++++++++++++-----------------------
 lib/schema.ncl |  20 ++++----
 2 files changed, 81 insertions(+), 73 deletions(-)

diff --git a/lib/files.ncl b/lib/files.ncl
index bbf11298..c6b0ea8d 100644
--- a/lib/files.ncl
+++ b/lib/files.ncl
@@ -1,86 +1,92 @@
 let nix = import "./nix-interop/nix.ncl" in
-{
-  File = {
-    target
-      | doc m%"
+let File = {
+  target
+    | doc m%"
         The file to write to.
         If null, defaults to the attribute name of the file.
       "%
-      | String
-      | optional,
-    content
-      | doc m%"
+    | String
+    | optional,
+  content
+    | doc m%"
         The content of the file.
       "%
-      | nix.derivation.NixString,
-    materialisation_method
-      : [| 'Symlink, 'Copy |]
-      | doc m%"
+    | nix.derivation.NixString,
+  materialisation_method
+    : [| 'Symlink, 'Copy |]
+    | doc m%"
         How the file should be materialized on-disk.
 
         Symlinking makes it easier to track where the files are coming from,
         but their target only exists after a first call to Organist, which
         might be undesirable.
       "%
-      | default
-      = 'Copy,
-    ..
-  },
-  Files = { _ : File },
-  NormaliseTargets = fun label files =>
-    files
-    |> std.record.map (fun name file_descr => file_descr & { target | default = name }),
-
-  Schema = {
-    files
-      | Files
-      | NormaliseTargets
-      | doc m%"
-        Set of files that should be generated in the project's directory.
-      "%
-      = {},
-    flake.apps.regenerate-files.program = nix-s%"%{regenerate_files files}/bin/regenerate-files"%,
-  },
-
-  regenerate_files | Files -> nix.derivation.Derivation = fun files_to_generate =>
-      let regnerate_one | String -> File -> nix.derivation.NixString = fun key file_descr =>
-          let file_content = file_descr.content in
-          let target = file_descr.target in
-          let copy_command =
-            match {
-              'Symlink => "ln -s",
-              'Copy => "cp",
-            }
-              file_descr.materialisation_method
-          in
-          let file_in_store =
-            nix.builtins.to_file
-              (nix.utils.escape_drv_name key)
-              file_content
-          in
-          nix-s%"
+    | default
+    = 'Copy,
+  ..
+}
+in
+let Files = { _ : File }
+in
+let NormaliseTargets = fun label files =>
+  files
+  |> std.record.map (fun name file_descr => file_descr & { target | default = name })
+in
+let regenerate_files | Files -> nix.derivation.Derivation = fun files_to_generate =>
+    let regnerate_one | String -> File -> nix.derivation.NixString = fun key file_descr =>
+        let file_content = file_descr.content in
+        let target = file_descr.target in
+        let copy_command =
+          match {
+            'Symlink => "ln -s",
+            'Copy => "cp",
+          }
+            file_descr.materialisation_method
+        in
+        let file_in_store =
+          nix.builtins.to_file
+            (nix.utils.escape_drv_name key)
+            file_content
+        in
+        nix-s%"
             rm -f %{target}
             echo "Regenerating %{target}"
 	    target_dir=$(dirname %{target})
 	    test "${target_dir}" != "." && mkdir -p "${target_dir}"
             %{copy_command} %{file_in_store} %{target}
           "%
-        in
-      {
-        name = "regenerate-files",
-        content.text =
-          files_to_generate
-          |> std.record.to_array
-          |> std.array.map (fun { field, value } => regnerate_one field value)
-          |> std.array.fold_left
-            (
-              fun acc elt =>
-                nix-s%"
+      in
+    {
+      name = "regenerate-files",
+      content.text =
+        files_to_generate
+        |> std.record.to_array
+        |> std.array.map (fun { field, value } => regnerate_one field value)
+        |> std.array.fold_left
+          (
+            fun acc elt =>
+              nix-s%"
                   %{acc}
                   %{elt}
                 "%
-            )
-            "",
-      }
-        | nix.builders.ShellApplication,
+          )
+          "",
+    }
+      | nix.builders.ShellApplication
+  in
+{
+  Schema = {
+    files
+      | Files
+      | NormaliseTargets
+      | doc m%"
+        Set of files that should be generated in the project's directory.
+      "%
+      = {},
+    flake.apps, # Forward declaration. Not great but would need some refactor to fix
+  },
+  config | Schema = {
+      files,
+      flake.apps.regenerate-files.program = nix-s%"%{regenerate_files files}/bin/regenerate-files"%,
+    },
 }
diff --git a/lib/schema.ncl b/lib/schema.ncl
index d8358c75..1da513af 100644
--- a/lib/schema.ncl
+++ b/lib/schema.ncl
@@ -47,21 +47,23 @@ let filegen = import "files.ncl" in
   #
   # The contract must be: what the Nix side of the code can "parse" without
   # erroring out.
-  OrganistExpression.Schema =
+  OrganistExpression =
     {
-      shells
-        | doc m%"
+      Schema = {
+        shells
+          | doc m%"
             The shells that will be entered by `nix develop`.
           "%
-        | OrganistShells,
-      flake
-        | doc m%"
+          | OrganistShells,
+        flake
+          | doc m%"
             The raw flake outputs that will be passed to Nix.
 
             These should follow the Nix flake outputs schema.
           "%
-        | FlakeOutputs
-        = {},
+          | FlakeOutputs
+          = {},
+      },
     }
-    & filegen.Schema
+    & filegen
 }

From 7ed577b4e6bcdad0b37c1a52db59b7d34beee6e2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Thu, 6 Jun 2024 19:32:30 +0200
Subject: [PATCH 03/13] Use a module for the direnv module

---
 examples/direnv/project.ncl | 27 ++++++++++++++-------------
 lib/direnv.ncl              | 23 ++++++++++++++---------
 2 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/examples/direnv/project.ncl b/examples/direnv/project.ncl
index bbceeef8..cfd0971d 100644
--- a/examples/direnv/project.ncl
+++ b/examples/direnv/project.ncl
@@ -1,18 +1,19 @@
 let inputs = import "./nickel.lock.ncl" in
 let organist = inputs.organist in
 
-{
-  shells = organist.shells.Bash,
+organist.OrganistExpression
+& organist.tools.direnv
+& {
+  Schema,
+  config | Schema = {
+      shells = organist.shells.Bash,
 
-  shells.build = {
-    packages = {},
-  },
+      shells.build = {
+        packages = {},
+      },
 
-  shells.dev = {
-    packages.direnv = organist.import_nix "nixpkgs#direnv"
-  },
-}
-  | (
-    organist.OrganistExpression
-    & organist.tools.direnv.Schema
-  )
+      shells.dev = {
+        packages.direnv = organist.import_nix "nixpkgs#direnv"
+      },
+    },
+} | organist.modules.T
diff --git a/lib/direnv.ncl b/lib/direnv.ncl
index 292eac9d..3707f44c 100644
--- a/lib/direnv.ncl
+++ b/lib/direnv.ncl
@@ -1,4 +1,6 @@
-{
+let files = import "files.ncl" in
+files
+& {
   Schema = {
     direnv = {
       enable
@@ -9,10 +11,13 @@
         | default
         = true,
     },
-    files =
-      if direnv.enable then
-        {
-          ".envrc".content = m%"
+  },
+  config | Schema = {
+      direnv,
+      files =
+        if direnv.enable then
+          {
+            ".envrc".content = m%"
             if ! has nix_direnv_version || ! nix_direnv_version 2.4.0; then
               source_url "https://raw.githubusercontent.com/nix-community/nix-direnv/2.4.0/direnvrc" "sha256-XQzUAvL6pysIJnRJyR7uVpmUSZfc7LSgWQwq/4mBr1U="
             fi
@@ -20,8 +25,8 @@
             source_env_if_exists ".envrc.private"
             use flake
           "%,
-        }
-      else
-        {},
-  },
+          }
+        else
+          {},
+    },
 }

From 6cfd81dedfe7a507c33228a6828c7242ca8327a2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Fri, 7 Jun 2024 05:45:17 +0200
Subject: [PATCH 04/13] Use a module for editorconfig

---
 examples/filegen/project.ncl | 44 +++++++++++++++++++-----------------
 lib/editorconfig.ncl         | 25 ++++++++++++--------
 2 files changed, 38 insertions(+), 31 deletions(-)

diff --git a/examples/filegen/project.ncl b/examples/filegen/project.ncl
index d86f437e..dd385795 100644
--- a/examples/filegen/project.ncl
+++ b/examples/filegen/project.ncl
@@ -1,29 +1,31 @@
 let inputs = import "./nickel.lock.ncl" in
 let organist = inputs.organist in
 
-{
-  shells = organist.shells.Bash,
+organist.OrganistExpression
+& organist.tools.editorconfig
+& {
+  Schema,
+  config | Schema = {
+      shells = organist.shells.Bash,
 
-  shells.build = {
-    packages = {},
-  },
+      shells.build = {
+        packages = {},
+      },
 
-  shells.dev = {
-    packages.hello = organist.import_nix "nixpkgs#hello",
-  },
+      shells.dev = {
+        packages.hello = organist.import_nix "nixpkgs#hello",
+      },
 
-  editorconfig.sections = {
-    "*".indent_style = 'space,
-    "*".indent_size = 2,
-    "*".insert_final_newline = true,
-    "Makefile".indent_style = 'tab,
-    "*.py" = {
-      indent_style = 'space,
-      indent_size = 4,
+      editorconfig.sections = {
+        "*".indent_style = 'space,
+        "*".indent_size = 2,
+        "*".insert_final_newline = true,
+        "Makefile".indent_style = 'tab,
+        "*.py" = {
+          indent_style = 'space,
+          indent_size = 4,
+        },
+      },
     },
-  },
 }
-  | (
-    organist.OrganistExpression
-    & organist.tools.editorconfig.Schema
-  )
+  | organist.modules.T
diff --git a/lib/editorconfig.ncl b/lib/editorconfig.ncl
index 932c5419..c4d04c4f 100644
--- a/lib/editorconfig.ncl
+++ b/lib/editorconfig.ncl
@@ -1,3 +1,4 @@
+let files = import "./files.ncl" in
 let IndentSize = fun label value =>
   if value == 'tab then
     value
@@ -68,7 +69,8 @@ let EditorConfigSchema = {
     = {},
 }
 in
-{
+files
+& {
   Schema = {
     editorconfig
       | doc m%"
@@ -77,14 +79,17 @@ in
       | EditorConfigSchema
       | default
       = {},
-    files =
-      if editorconfig.sections != {} then
-        {
-          ".editorconfig" = {
-            content = generate editorconfig.is_root editorconfig.sections,
-          }
-        }
-      else
-        {},
   },
+  config | Schema = {
+      editorconfig,
+      files =
+        if editorconfig.sections != {} then
+          {
+            ".editorconfig" = {
+              content = generate editorconfig.is_root editorconfig.sections,
+            }
+          }
+        else
+          {},
+    },
 }

From 74d2bee715ff02d3833d6a312ebbd558dac0e254 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Fri, 7 Jun 2024 05:54:45 +0200
Subject: [PATCH 05/13] Use a module for the services config

---
 examples/services/project.ncl | 65 ++++++++++++++++++-----------------
 lib/services.ncl              | 38 +++++++++++---------
 2 files changed, 55 insertions(+), 48 deletions(-)

diff --git a/examples/services/project.ncl b/examples/services/project.ncl
index f2b8a624..37656acc 100644
--- a/examples/services/project.ncl
+++ b/examples/services/project.ncl
@@ -4,43 +4,46 @@ let organist = inputs.organist in
 let postgres_listen_port = 64441 in
 let redis_listen_port = 64442 in
 
-{
-  shells = organist.shells.Bash,
+organist.OrganistExpression
+& organist.tools.editorconfig
+& organist.services
+& {
 
-  shells.build = {
-    packages = {},
-  },
+  Schema,
+  config | Schema = {
+      shells = organist.shells.Bash,
 
-  shells.dev = {
-    packages = {
-      postgresql = organist.import_nix "nixpkgs#postgresql",
-      redis = organist.import_nix "nixpkgs#redis",
-      honcho = organist.import_nix "nixpkgs#honcho",
-    },
-    env.POSTGRES_PORT = "%{std.to_string postgres_listen_port}",
-    env.REDIS_URI = "redis://localhost:%{std.to_string redis_listen_port}",
-  },
+      shells.build = {
+        packages = {},
+      },
+
+      shells.dev = {
+        packages = {
+          postgresql = organist.import_nix "nixpkgs#postgresql",
+          redis = organist.import_nix "nixpkgs#redis",
+          honcho = organist.import_nix "nixpkgs#honcho",
+        },
+        env.POSTGRES_PORT = "%{std.to_string postgres_listen_port}",
+        env.REDIS_URI = "redis://localhost:%{std.to_string redis_listen_port}",
+      },
 
-  services = {
-    postgres =
-      let start_script =
-        {
-          name = "start-postgres",
-          runtime_inputs.postgres = organist.import_nix "nixpkgs#postgresql",
-          content.text = nix-s%"
+      services = {
+        postgres =
+          let start_script =
+            {
+              name = "start-postgres",
+              runtime_inputs.postgres = organist.import_nix "nixpkgs#postgresql",
+              content.text = nix-s%"
           mkdir -p ./.postgres-data
           initdb ./.postgres-data
           postgres -D ./.postgres-data -k "$PWD/.postgres-data" -p %{std.to_string postgres_listen_port}
 
         "%
-        } | organist.nix.builders.ShellApplication
-      in
-      nix-s%"%{start_script}/bin/start-postgres"%,
-    redis = nix-s%"%{organist.import_nix "nixpkgs#redis"}/bin/redis-server --port %{std.to_string redis_listen_port}"%,
-  },
+            } | organist.nix.builders.ShellApplication
+          in
+          nix-s%"%{start_script}/bin/start-postgres"%,
+        redis = nix-s%"%{organist.import_nix "nixpkgs#redis"}/bin/redis-server --port %{std.to_string redis_listen_port}"%,
+      },
+    },
 }
-  | (
-    organist.OrganistExpression
-    & organist.tools.editorconfig.Schema
-    & organist.services.Schema
-  )
+  | organist.modules.T
diff --git a/lib/services.ncl b/lib/services.ncl
index 30990cce..39404ddb 100644
--- a/lib/services.ncl
+++ b/lib/services.ncl
@@ -36,21 +36,25 @@ let generate_procfile | ProcfileSchema -> nix.derivation.NixString = fun schema
       | { _ : nix.derivation.NixString }
       | default
       = {},
-    flake.apps =
-      if services != {} then
-        let procfile = nix.builtins.to_file "Procfile" (generate_procfile services) in
-        {
-          start-services.type = "app",
-          start-services.program | nix.derivation.NixString =
-              let run =
-                nix.builders.ShellApplication
-                & {
-                  name = "start-services",
-                  content.text = nix-s%"exec %{nix.import_nix "nixpkgs#honcho"}/bin/honcho -f %{procfile} "$@""%
-                }
-              in nix-s%"%{run}/bin/start-services"%
-        }
-      else
-        {},
-  }
+    flake.apps,
+  },
+  config | Schema = {
+      services,
+      flake.apps =
+        if services != {} then
+          let procfile = nix.builtins.to_file "Procfile" (generate_procfile services) in
+          {
+            start-services.type = "app",
+            start-services.program | nix.derivation.NixString =
+                let run =
+                  nix.builders.ShellApplication
+                  & {
+                    name = "start-services",
+                    content.text = nix-s%"exec %{nix.import_nix "nixpkgs#honcho"}/bin/honcho -f %{procfile} "$@""%
+                  }
+                in nix-s%"%{run}/bin/start-services"%
+          }
+        else
+          {},
+    },
 }

From f677689132338ebd4c3a3317e986001a872e109d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Fri, 7 Jun 2024 05:57:14 +0200
Subject: [PATCH 06/13] Migrate the remaining examples to the schema structure

---
 examples/c-hello-world/project.ncl      | 44 ++++++++++++++-----------
 examples/raw_nix_expression/project.ncl | 34 ++++++++++---------
 2 files changed, 43 insertions(+), 35 deletions(-)

diff --git a/examples/c-hello-world/project.ncl b/examples/c-hello-world/project.ncl
index 2a9fd564..9aca4def 100644
--- a/examples/c-hello-world/project.ncl
+++ b/examples/c-hello-world/project.ncl
@@ -1,30 +1,34 @@
 let inputs = import "./nickel.lock.ncl" in
 let organist = inputs.organist in
 
-{
-  flake.packages."default" = flake.packages.hello,
-  flake.packages.hello =
-    organist.nix.builders.NixpkgsPkg
-    & {
-      name = "hello",
-      version = "0.1",
-      structured_env.buildInputs = {
-        gcc = organist.import_nix "nixpkgs#gcc",
-        coreutils = organist.import_nix "nixpkgs#coreutils",
-        bash = organist.import_nix "nixpkgs#bash",
-      },
-      env.src = organist.nix.builtins.import_file ".",
-      env.buildCommand =
-        nix-s%"
+organist.OrganistExpression
+& {
+  Schema,
+  config | Schema = {
+      flake.packages."default" = flake.packages.hello,
+      flake.packages.hello =
+        organist.nix.builders.NixpkgsPkg
+        & {
+          name = "hello",
+          version = "0.1",
+          structured_env.buildInputs = {
+            gcc = organist.import_nix "nixpkgs#gcc",
+            coreutils = organist.import_nix "nixpkgs#coreutils",
+            bash = organist.import_nix "nixpkgs#bash",
+          },
+          env.src = organist.nix.builtins.import_file ".",
+          env.buildCommand =
+            nix-s%"
           cp $src/* .
           mkdir -p $out/{include,lib}
           gcc -shared hello.c -o libhello.so
           cp *.so $out/lib/
           cp hello.h $out/include/hello.h
         "%
-          | organist.nix.derivation.NixString,
-    },
+              | organist.nix.derivation.NixString,
+        },
 
-  shells = organist.shells.Bash,
-  shells.build.packages.hello = flake.packages.hello,
-} | organist.OrganistExpression
+      shells = organist.shells.Bash,
+      shells.build.packages.hello = flake.packages.hello,
+    },
+} | organist.modules.T
diff --git a/examples/raw_nix_expression/project.ncl b/examples/raw_nix_expression/project.ncl
index e2d0f347..04265a00 100644
--- a/examples/raw_nix_expression/project.ncl
+++ b/examples/raw_nix_expression/project.ncl
@@ -1,23 +1,27 @@
 let inputs = import "./nickel.lock.ncl" in
 let organist = inputs.organist in
 
-{
-  shells = organist.shells.Bash,
+organist.OrganistExpression
+& {
+  Schema,
+  config | Schema = {
+      shells = organist.shells.Bash,
 
-  shells.build = {
-    packages = {},
-  },
+      shells.build = {
+        packages = {},
+      },
 
-  shells.dev = {
-    packages.python =
-      organist.nix.derivation.CallNix
-      & {
-        function = m%"
+      shells.dev = {
+        packages.python =
+          organist.nix.derivation.CallNix
+          & {
+            function = m%"
           { python }: python.withPackages (p: [p.pyyaml])
         "%,
-        args = {
-          python = organist.import_nix "nixpkgs#python3"
-        },
+            args = {
+              python = organist.import_nix "nixpkgs#python3"
+            },
+          },
       },
-  },
-} | organist.OrganistExpression
+    },
+} | organist.modules.T

From 6c9b1adf47854961bceeef24af903b5d570ad219 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Fri, 7 Jun 2024 06:10:14 +0200
Subject: [PATCH 07/13] Migrate the project to the module system

---
 templates/default/project.ncl | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/templates/default/project.ncl b/templates/default/project.ncl
index e7cb8bc4..82840353 100644
--- a/templates/default/project.ncl
+++ b/templates/default/project.ncl
@@ -1,15 +1,19 @@
 let inputs = import "./nickel.lock.ncl" in
 let organist = inputs.organist in
 
-{
-  shells = organist.shells.Bash,
+organist.OrganistExpression
+& {
+  Schema,
+  config | Schema = {
+      shells = organist.shells.Bash,
 
-  shells.build = {
-    packages = {},
-  },
+      shells.build = {
+        packages = {},
+      },
 
-  shells.dev = {
-    packages.hello = organist.import_nix "nixpkgs#hello",
-  },
+      shells.dev = {
+        packages.hello = organist.import_nix "nixpkgs#hello",
+      },
+    },
 }
-  | organist.OrganistExpression
+  | organist.modules.T

From fd6e42bdd286d328a850033f5723fac2a77b5cf5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Fri, 7 Jun 2024 06:19:28 +0200
Subject: [PATCH 08/13] Mirror the module system in the documentation

---
 RELEASES.md                  |  7 +++++++
 doc/dependency-management.md | 24 ++++++++++++++----------
 doc/services.md              | 10 ++++------
 3 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/RELEASES.md b/RELEASES.md
index 82de2cc0..7c1a633a 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -1,3 +1,10 @@
+## HEAD
+
+### Breaking changes
+
+- The overall structure has been reshaped to use a NixOS-modules-like interface.
+  XXX: Extend and explain how to migrate
+
 ## Version 0.1 (2023-11-16)
 
 First release (🎉)
diff --git a/doc/dependency-management.md b/doc/dependency-management.md
index d01939f1..66d75439 100644
--- a/doc/dependency-management.md
+++ b/doc/dependency-management.md
@@ -10,17 +10,21 @@ After running `nix flake init`, you should end-up with a `project.ncl` looking l
 let inputs = import "./nickel.lock.ncl" in
 let organist = inputs.organist in
 
-{
-  shells = organist.shells.Bash,
-
-  shells.build = {
-    packages = {},
-  },
-
-  shells.dev = {
-    packages.hello = organist.lib.import_nix "nixpkgs#hello",
+organist.contracts.OrganistExpression
+& {
+  Schema,
+  config | Schema = {
+    shells = organist.shells.Bash,
+
+    shells.build = {
+      packages = {},
+    },
+
+    shells.dev = {
+      packages.hello = organist.lib.import_nix "nixpkgs#hello",
+    },
   },
-} | organist.contracts.OrganistExpression
+} | organist.modules.T
 ```
 
 This defines two variants of the shell: `build` and `dev`, both of which inherit from `organist.shells.Bash` (more precisely, `build` inherits from `organist.shells.Bash.build` and `dev` inherits from `organist.shells.Bash.dev`).
diff --git a/doc/services.md b/doc/services.md
index 684eb55f..19096f05 100644
--- a/doc/services.md
+++ b/doc/services.md
@@ -8,13 +8,11 @@ For instance, if the `project.ncl` contains:
 
 ```nickel
 let redis_listen_port = 64442 in
-{
-  services.redis = nix-s%"%{organist.import_nix "nixpkgs#redis"}/bin/redis-server --port %{std.to_string redis_listen_port}"%,
+organist.OrganistExpression
+& organist.services
+& {
+  config.services.redis = nix-s%"%{organist.import_nix "nixpkgs#redis"}/bin/redis-server --port %{std.to_string redis_listen_port}"%,
 }
-  | (
-    organist.OrganistExpression
-    & organist.services.Schema
-  )
 ```
 
 then running `nix run .#start-services start` will run a local `redis` instance listening on port 64442.

From 12eaa6415a109c4d2b38a3b7109c3dac51bddc30 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Mon, 17 Jun 2024 10:23:40 +0200
Subject: [PATCH 09/13] document the migration to the module system

---
 doc/migrate-from-0.1.md | 74 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 doc/migrate-from-0.1.md

diff --git a/doc/migrate-from-0.1.md b/doc/migrate-from-0.1.md
new file mode 100644
index 00000000..dd8ea7f5
--- /dev/null
+++ b/doc/migrate-from-0.1.md
@@ -0,0 +1,74 @@
+# Migrating from 0.1
+
+Since 0.2, Organist uses a [module system] for the configuration.
+This means that the `project.ncl` is now a module, with a slightly different interface.
+
+## Migrating `project.ncl`
+
+In the vast majority of cases, the migration consists of three things:
+
+1. Declare a new `Schema` field;
+2. Move all the options under a `config` field;
+3. Replace the schema by `organist.module.T`, and instead merge the config with the previous schema.
+
+As an example is probably more eloquent, this means rewriting:
+
+```nickel
+{
+  shells = …,
+  foo = bar,
+  …
+} | (organist.OrganistExpression & organist.something.Schema & organist.somethingElse.Schema)
+```
+
+into:
+
+```nickel
+organist.OrganistExpression
+& organist.something
+& organist.somethingElse
+& {
+  Schema,
+  config | Schema = {
+    shells = …,
+    foo = bar,
+    …
+  },
+} | organist.module.T
+```
+
+## Migrating custom modules
+
+Migrating custom modules is similar, except that
+1. The module system now separates the _declaration_ of options from their _definition_ (respectively the `Schema` and `config` fields)
+2. Modules must now merge with all of their dependencies (the modules whose option they use).
+
+For instance, an hypothetical module like the one below:
+
+```nickel
+{
+  readme.content
+    | doc "Content of the README file"
+    | String,
+  files."foo".content = readme.content,
+}
+```
+
+should be rewritten to
+
+```nickel
+(import organist.files) # Because we set the `files` option which is defined there
+& {
+  # New options defined by the module
+  Schema = {
+    readme.content
+      | doc "Content of the README file"
+      | String,
+  },
+  # Implementation of the module, setting options from other modules
+  config | Schema = {
+    readme,
+    files."foo".content = readme.content,
+  },
+}
+```

From 9a4ee05880f7b22eae1ee09ba9dcee7bfa8fd4d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <7226587+thufschmitt@users.noreply.github.com>
Date: Wed, 19 Jun 2024 18:01:46 +0200
Subject: [PATCH 10/13] Apply suggestions from code review

Co-authored-by: Yann Hamdaoui <yann.hamdaoui@gmail.com>
---
 lib/modules/main.ncl | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/modules/main.ncl b/lib/modules/main.ncl
index 3223cb4d..93fe472b 100644
--- a/lib/modules/main.ncl
+++ b/lib/modules/main.ncl
@@ -7,6 +7,7 @@
     = {
       config | Schema = {},
       Schema
+        | { .. }
         | not_exported
         = {},
       "$__organist_type" | force = "module",
@@ -15,7 +16,7 @@
   submodules
     | { _ : T } -> T
     | doc m%"
-      Joins all the given module into a single one, prefixing all the keys of
+      Joins all the given modules into a single one, prefixing all the keys of
       their options with the key of the corresponding module.
 
       ```nickel

From e43b559550c84850357bb28b264b788fd9ffd166 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Wed, 19 Jun 2024 17:58:21 +0200
Subject: [PATCH 11/13] Remove a useless module merge function

Just an alias for `&`, but which breaks the LSP
---
 lib/modules/main.ncl | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/lib/modules/main.ncl b/lib/modules/main.ncl
index 93fe472b..0a9fd080 100644
--- a/lib/modules/main.ncl
+++ b/lib/modules/main.ncl
@@ -38,8 +38,4 @@
         Schema = schemas,
         config | Schema = configs,
       } | T,
-
-  merge2
-    | T -> T -> T
-    = fun m1 m2 => m1 & m2,
 }

From 04bfa741c2371fca1bfbfefdafcf4367d6b7ebe3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <7226587+thufschmitt@users.noreply.github.com>
Date: Wed, 19 Jun 2024 18:38:01 +0200
Subject: [PATCH 12/13] Only export the `flake` field of the nickel config
 (#208)

Makes it clear what Nix has (or not) access to.

Also makes it possible in the future to fearlessly use enums in the
config, as they won't be exported
---
 flake.nix      | 10 ++++------
 lib/lib.nix    |  6 +++---
 lib/schema.ncl |  4 ++++
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/flake.nix b/flake.nix
index 80e06fac..32a06a8f 100644
--- a/flake.nix
+++ b/flake.nix
@@ -44,17 +44,15 @@
         then {}
         else {
           inherit nickelOutputs;
-          packages = nickelOutputs.packages or {} // nickelOutputs.flake.packages or {};
-          checks = nickelOutputs.flake.checks or {};
+          packages = nickelOutputs.packages or {};
+          checks = nickelOutputs.checks or {};
           # Can't define this app in Nickel, yet
           apps =
             {
               regenerate-lockfile = lib.regenerateLockFileApp lockFileContents;
             }
-            // nickelOutputs.flake.apps or {};
-          # We can't just copy `shells` to `flake.devShells` in the contract
-          # because of a bug in Nickel: https://github.com/tweag/nickel/issues/1630
-          devShells = nickelOutputs.shells or {} // nickelOutputs.flake.devShells or {};
+            // nickelOutputs.apps or {};
+          devShells = nickelOutputs.devShells or {};
         });
 
     computedOutputs = outputsFromNickel ./. (inputs // {organist = self;}) {
diff --git a/lib/lib.nix b/lib/lib.nix
index 6abbea84..3eaa119a 100644
--- a/lib/lib.nix
+++ b/lib/lib.nix
@@ -157,7 +157,7 @@
       in
       let organist = (import "${src}/nickel.lock.ncl").organist in
 
-      let nickel_expr | (organist.OrganistExpression & {..}) =
+      let nickel_expr =
         import "${src}/${nickelFile}" in
 
       nickel_expr & params
@@ -184,13 +184,13 @@
           cat > eval.ncl <<EOF
           ${nickelWithImports "sources"}
           EOF
-          ${nickel}/bin/nickel export eval.ncl > $out
+          ${nickel}/bin/nickel export eval.ncl --field config.flake > $out
         ''
       else ''
         cat > eval.ncl <<EOF
         ${nickelWithImports sources}
         EOF
-        ${nickel}/bin/nickel export eval.ncl > $out
+        ${nickel}/bin/nickel export eval.ncl --field config.flake > $out
       ''
     );
 
diff --git a/lib/schema.ncl b/lib/schema.ncl
index 1da513af..207b05d7 100644
--- a/lib/schema.ncl
+++ b/lib/schema.ncl
@@ -64,6 +64,10 @@ let filegen = import "files.ncl" in
           | FlakeOutputs
           = {},
       },
+      config | Schema = {
+          shells,
+          flake.devShells = shells,
+        },
     }
     & filegen
 }

From 88b3dc7cc95997b8f59cd37099c6293188e7f598 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <7226587+thufschmitt@users.noreply.github.com>
Date: Wed, 19 Jun 2024 19:21:50 +0200
Subject: [PATCH 13/13] =?UTF-8?q?Add=20an=20=E2=80=9CExample=E2=80=9D=20he?=
 =?UTF-8?q?ader=20to=20a=20documentation=20field?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Align with the usual Nickel convention

Co-authored-by: Yann Hamdaoui <yann.hamdaoui@gmail.com>
---
 lib/modules/main.ncl | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/modules/main.ncl b/lib/modules/main.ncl
index 0a9fd080..bbbd1247 100644
--- a/lib/modules/main.ncl
+++ b/lib/modules/main.ncl
@@ -19,6 +19,8 @@
       Joins all the given modules into a single one, prefixing all the keys of
       their options with the key of the corresponding module.
 
+      # Example
+
       ```nickel
       submodules {
           mod1 = { Schema.foo | Number, config.foo = 1 },