use mkNakedShell from devshell for less noisy shell

Fixes cachix#79
thenonameguy · Nov 21, 2022 · 530a99b · 530a99b
1 parent 280f550
commit 530a99b
Show file tree

Hide file tree

Showing 2 changed files with 136 additions and 34 deletions.
diff --git a/src/modules/mkNakedShell.nix b/src/modules/mkNakedShell.nix
@@ -0,0 +1,94 @@
+# copied from https://github.com/amarshall/devshell/blob/917a891e98ca26c006a6be1fdb3335a74720c237/nix/mkNakedShell.nix#L1
+# to support inputDerivation for easy CI caching as well: https://github.com/numtide/devshell/pull/226
+{ bashInteractive
+, coreutils
+, system
+, writeTextFile
+}:
+let
+  bashPath = "${bashInteractive}/bin/bash";
+  stdenv = writeTextFile {
+    name = "naked-stdenv";
+    destination = "/setup";
+    text = ''
+      # Fix for `nix develop`
+      : ''${outputs:=out}
+
+      runHook() {
+        eval "$shellHook"
+        unset runHook
+      }
+    '';
+  };
+in
+{ name
+, # A path to a buildEnv that will be loaded by the shell.
+  # We assume that the buildEnv contains an ./env.bash script.
+  profile
+, shellHook ? ""
+, meta ? { }
+, passthru ? { }
+}:
+let
+  derivationArg = {
+    inherit name system;
+
+    # `nix develop` actually checks and uses builder. And it must be bash.
+    builder = bashPath;
+
+    # Bring in the dependencies on `nix-build`
+    args = [ "-ec" "${coreutils}/bin/ln -s ${profile} $out; exit 0" ];
+
+    # $stdenv/setup is loaded by nix-shell during startup.
+    # https://github.com/nixos/nix/blob/377345e26f1ac4bbc87bb21debcc52a1d03230aa/src/nix-build/nix-build.cc#L429-L432
+    stdenv = stdenv;
+
+    # The shellHook is loaded directly by `nix develop`. But nix-shell
+    # requires that other trampoline.
+    shellHook = ''
+      # Remove all the unnecessary noise that is set by the build env
+      unset NIX_BUILD_TOP NIX_BUILD_CORES NIX_STORE
+      unset TEMP TEMPDIR TMP TMPDIR
+      # $name variable is preserved to keep it compatible with pure shell https://github.com/sindresorhus/pure/blob/47c0c881f0e7cfdb5eaccd335f52ad17b897c060/pure.zsh#L235
+      unset builder out shellHook stdenv system
+      # Flakes stuff
+      unset dontAddDisableDepTrack outputs
+
+      # For `nix develop`. We get /noshell on Linux and /sbin/nologin on macOS.
+      if [[ "$SHELL" == "/noshell" || "$SHELL" == "/sbin/nologin" ]]; then
+        export SHELL=${bashPath}
+      fi
+
+      # https://github.com/numtide/devshell/issues/158
+      PATH=''${PATH#/path-not-set:}
+
+      export PATH="${profile}/bin:$PATH"
+
+      ${shellHook}
+    '';
+  };
+in
+(derivation derivationArg) // {
+  inherit meta passthru;
+
+  # https://github.com/NixOS/nixpkgs/blob/41f7e338216fd7f5e57817c4f8e148d42fb88b24/pkgs/stdenv/generic/make-derivation.nix#L486-L504
+  inputDerivation = derivation (derivationArg // {
+    # Add a name in case the original drv didn't have one
+    name = derivationArg.name or "inputDerivation";
+    # This always only has one output
+    outputs = [ "out" ];
+
+    # Propagate the original builder and arguments, since we override
+    # them and they might contain references to build inputs
+    _derivation_original_builder = derivationArg.builder;
+    _derivation_original_args = derivationArg.args;
+
+    builder = bashPath;
+    # The bash builtin `export` dumps all current environment variables,
+    # which is where all build input references end up (e.g. $PATH for
+    # binaries). By writing this to $out, Nix can find and register
+    # them as runtime dependencies (since Nix greps for store paths
+    # through $out to find them)
+    args = [ "-c" "export > $out" ];
+  });
+} // passthru
diff --git a/src/modules/top-level.nix b/src/modules/top-level.nix
@@ -71,39 +71,47 @@ in
     ./update-check.nix
   ] ++ map (name: ./. + "/languages/${name}") (builtins.attrNames (builtins.readDir ./languages));
 
-  config = {
-    # TODO: figure out how to get relative path without impure mode
-    env.DEVENV_ROOT = builtins.getEnv "PWD";
-    env.DEVENV_DOTFILE = config.env.DEVENV_ROOT + "/.devenv";
-    env.DEVENV_STATE = config.env.DEVENV_DOTFILE + "/state";
-
-    procfile = pkgs.writeText "procfile"
-      (lib.concatStringsSep "\n" (lib.mapAttrsToList (name: process: "${name}: ${process.exec}") config.processes));
-
-    procfileEnv = pkgs.writeText "procfile-env"
-      (lib.concatStringsSep "\n" (lib.mapAttrsToList (name: value: "${name}=${toString value}") config.env));
-
-    enterShell = ''
-      export PS1="(devenv) $PS1"
+  config =
+    let
+      mkNakedShell = pkgs.callPackage ./mkNakedShell.nix { };
+    in
+    {
+      # TODO: figure out how to get relative path without impure mode
+      env.DEVENV_ROOT = builtins.getEnv "PWD";
+      env.DEVENV_DOTFILE = config.env.DEVENV_ROOT + "/.devenv";
+      env.DEVENV_STATE = config.env.DEVENV_DOTFILE + "/state";
+
+      procfile = pkgs.writeText "procfile"
+        (lib.concatStringsSep "\n" (lib.mapAttrsToList (name: process: "${name}: ${process.exec}") config.processes));
+
+      procfileEnv = pkgs.writeText "procfile-env"
+        (lib.concatStringsSep "\n" (lib.mapAttrsToList (name: value: "${name}=${toString value}") config.env));
+
+      enterShell = ''
+        export PS1="(devenv) $PS1"
       
-      # note what environments are active, but make sure we don't repeat them
-      if [[ ! "$DIRENV_ACTIVE" =~ (^|:)"$PWD"(:|$) ]]; then
-        export DIRENV_ACTIVE="$PWD:$DIRENV_ACTIVE"
-      fi
-
-      # devenv helper
-      if [ ! type -p direnv &>/dev/null && -f .envrc ]; then
-        echo "You have .envrc but direnv command is not installed."
-        echo "Please install direnv: https://direnv.net/docs/installation.html"
-      fi
-    '';
-
-    shell = pkgs.mkShell ({
-      name = "devenv";
-      packages = config.packages;
-      shellHook = config.enterShell;
-    } // config.env);
-
-    ci = [ config.shell config.procfile ];
-  };
+        # note what environments are active, but make sure we don't repeat them
+        if [[ ! "$DIRENV_ACTIVE" =~ (^|:)"$PWD"(:|$) ]]; then
+          export DIRENV_ACTIVE="$PWD:$DIRENV_ACTIVE"
+        fi
+
+        # devenv helper
+        if [ ! type -p direnv &>/dev/null && -f .envrc ]; then
+          echo "You have .envrc but direnv command is not installed."
+          echo "Please install direnv: https://direnv.net/docs/installation.html"
+        fi
+      '';
+
+      shell = mkNakedShell {
+        name = "devenv";
+        profile = pkgs.buildEnv {
+          name = "devenv-profile";
+          paths = config.packages;
+        };
+        shellHook = config.enterShell;
+        passthru = config.env;
+      };
+
+      ci = [ config.shell config.procfile ];
+    };
 }