Make the hooks more verbose

Print the hook name when it runs.
Makes it easier to understand what's going on

Author: Théophane Hufschmitt

Diff for: lib/files.ncl

@@ -63,7 +63,7 @@ let nix = import "./nix-interop/nix.ncl" in
     shells.build.hooks =
       if filegen_hook.enable then
         {
-          filegen_hook = nix-s%"
+          filegen_hook.content = nix-s%"
             %{regenerate_files files}/bin/regenerate-files
           "%
         }

Diff for: lib/nix-interop/builders.ncl

@@ -76,29 +76,6 @@ in
       }
         | NickelPkg,
 
-  Shell
-    | doc m%"
-      A derivation that is to be used as a shell, e.g. with `nix develop`.
-      Analogous to `mkShell`.
-    "%
-    =
-      NixpkgsPkg
-      & {
-        hooks | doc "Bash scripts to run when entering the shell" = {},
-
-        name | default = "shell",
-        version | default = "dev",
-        packages | doc "Packages to be added to the shell, setting PATH, LD_LIBRARY_PATH and other variables as needed" = {},
-
-        env.buildCommand = nix-s%"
-          echo "This derivation is not supposed to be built" 1>&2 1>/dev/null
-          exit 1
-        "%,
-        env.shellHook = concat_strings_sep "\n" (std.record.values hooks),
-        structured_env.nativeBuildInputs = packages,
-      }
-        | NickelPkg,
-
   ShellApplication
     | doc m%"
       A derivation that writes contents of `content.file` to `bin/$name` in the output and makes it executable.

Diff for: lib/nix-interop/shells.ncl

@@ -1,4 +1,3 @@
-let builders = import "builders.ncl" in
 let nix_builtins = import "builtins.ncl" in
 
 let concat_strings_sep = fun sep values =>
@@ -9,6 +8,7 @@ let concat_strings_sep = fun sep values =>
 in
 
 {
+  Base = import "./shells/base.ncl",
   Bash = import "./shells/bash.ncl",
   Rust = import "./shells/rust.ncl",
 
@@ -95,9 +95,9 @@ in
       build.packages.opam = nix_builtins.import_nix "nixpkgs#opam",
       dev.packages.ocaml-lsp = nix_builtins.import_nix "nixpkgs#ocamlPackages.ocaml-lsp",
 
-      dev.hooks.enter_opam_env = m%"
+      dev.hooks.enter_opam_env.content = m%"
         echo "==> Reloading the OPAM environment."
-        echo "==> Set 'shells.dev.hooks.enter_opam_env' to false to disable."
+        echo "==> Set 'shells.dev.hooks.enter_opam_env' to `""` to disable."
         eval $(opam env)
       "%,
     },

Diff for: lib/nix-interop/shells/base.ncl

@@ -0,0 +1,82 @@
+let builders = import "../builders.ncl" in
+let derivation = import "../derivation.ncl" in
+
+let Hook = {
+  name
+    | doc m%"
+        The name of the hook.
+        If null, defaults to the attribute name.
+      "%
+    | String
+    | optional,
+  enabled
+    | doc m%"
+      Whether to run the hook
+    "%
+    | Bool
+    | default
+    = true,
+  verbose
+    | doc m%"
+      Whether to announce when the hook runs
+    "%
+    | Bool
+    | default
+    = true,
+  content
+    | doc m%"
+        The bash snippet to run
+      "%
+    | derivation.NixString,
+}
+in
+let concat_strings_sep = fun sep values =>
+  if std.array.length values == 0 then
+    ""
+  else
+    std.array.reduce_left (fun acc value => nix-s%"%{acc}%{sep}%{value}"%) values
+in
+
+let hook_to_string | Hook -> derivation.NixString = fun hook =>
+    if hook.enabled then
+      let header =
+        if hook.verbose then
+          nix-s%"
+            echo -e '\033[34;1m==> Running hook %{hook.name}\033[0m'
+          "%
+        else
+          nix-s%""%
+      in
+
+      nix-s%"
+        %{header}
+        %{hook.content}
+      "%
+    else
+      nix-s%""%
+  in
+let NormaliseNames = fun label items =>
+  items
+  |> std.record.map (fun item_name item => item & { name | default = item_name })
+in
+
+builders.NixpkgsPkg
+& {
+  hooks
+    | doc "Bash scripts to run when entering the shell"
+    | { _ : Hook }
+    | NormaliseNames
+    = {},
+
+  name | default = "shell",
+  version | default = "dev",
+  packages | doc "Packages to be added to the shell, setting PATH, LD_LIBRARY_PATH and other variables as needed" = {},
+
+  env.buildCommand = nix-s%"
+          echo "This derivation is not supposed to be built" 1>&2 1>/dev/null
+          exit 1
+        "%,
+  env.shellHook = concat_strings_sep "\n" (std.record.values hooks |> std.array.map hook_to_string),
+  structured_env.nativeBuildInputs = packages,
+}
+  | builders.NickelPkg

Diff for: lib/nix-interop/shells/bash.ncl

@@ -1,8 +1,9 @@
 let builders = import "../builders.ncl" in
+let base = import "./base.ncl" in
 let nix_builtins = import "../builtins.ncl" in
 {
   build =
-    builders.Shell
+    base
     & {
       packages = {
         bash = nix_builtins.import_nix "nixpkgs#bash",