From 59aba7607507193587be7c24229dc71066e3ae87 Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Tue, 29 Nov 2022 16:19:19 +0100
Subject: [PATCH] Ability to use taskdir as flake; change nixpkgs syntax

---
 example/example-batch.hcl   | 27 +++++++++++++++++++++++++--
 example/example-service.hcl | 22 +++++++++++-----------
 example/flake.nix           | 18 ++++++++++++++++++
 nix2/driver.go              |  4 ++--
 nix2/nix.go                 |  5 +++--
 5 files changed, 59 insertions(+), 17 deletions(-)
 create mode 100644 example/flake.nix

diff --git a/example/example-batch.hcl b/example/example-batch.hcl
index a4dc946..15635f9 100644
--- a/example/example-batch.hcl
+++ b/example/example-batch.hcl
@@ -12,8 +12,11 @@ job "nix2-example-batch" {
       driver = "nix2"
 
       config {
+        # Packages contains a list of Nix flakes to include in the environement.
+        # Entries that start with # will be relative to nixpkgs.
+        # Otherwise, they are flake names that are passed directly to Nix build
         packages = [
-          "hello"   # equivalent to "github:nixos/nixpkgs/nixos-22.05#hello"
+          "#hello"   # equivalent to "github:nixos/nixpkgs/nixos-22.05#hello"
         ]
         command = "hello"
       }
@@ -31,7 +34,7 @@ job "nix2-example-batch" {
 
       config {
         packages = [
-          "curl", "cacert"
+          "#curl", "#cacert"
         ]
         command = "curl"
         args = [
@@ -42,5 +45,25 @@ job "nix2-example-batch" {
         SSL_CERT_FILE = "/etc/ssl/certs/ca-bundle.crt"
       }
     }
+
+    # This example show how to use a flake defined from a file
+    task "nix-hello-flake" {
+      driver = "nix2"
+
+      config {
+        # Packages contains a list of Nix flakes to include in the environement.
+        # Entries that start with # will be relative to nixpkgs.
+        # Otherwise, they are flake names that are passed directly to Nix build
+        packages = [
+          ".#hello"
+        ]
+        command = "hello"
+      }
+
+      template {
+        data = file("flake.nix")
+        destination = "flake.nix"
+      }
+    }
   }
 }
diff --git a/example/example-service.hcl b/example/example-service.hcl
index 03ba0d3..2f65435 100644
--- a/example/example-service.hcl
+++ b/example/example-service.hcl
@@ -13,17 +13,17 @@ job "nix2-example-service" {
 
       config {
         packages = [
-          "python3",
-          "bash",
-          "coreutils",
-          "curl",
-          "nix",
-          "git",
-          "cacert",
-          "strace",
-          "gnugrep",
-          "findutils",
-          "mount",
+          "#python3",
+          "#bash",
+          "#coreutils",
+          "#curl",
+          "#nix",
+          "#git",
+          "#cacert",
+          "#strace",
+          "#gnugrep",
+          "#findutils",
+          "#mount",
         ]
         command = "python3"
         args = [ "-m", "http.server", "8080" ]
diff --git a/example/flake.nix b/example/flake.nix
new file mode 100644
index 0000000..3e48ddb
--- /dev/null
+++ b/example/flake.nix
@@ -0,0 +1,18 @@
+{
+  description = "A very basic flake";
+
+  outputs = { self, nixpkgs }:
+  let
+    pkgs = import nixpkgs { system = "x86_64-linux"; };
+    hello = pkgs.writeScriptBin "hello" ''
+      #!${pkgs.bash}/bin/bash
+      echo "Hello from bash script!"
+    '';
+  in {
+
+    packages.x86_64-linux.hello = hello;
+
+    packages.x86_64-linux.default = self.packages.x86_64-linux.hello;
+
+  };
+}
diff --git a/nix2/driver.go b/nix2/driver.go
index 96bbf42..cba3bee 100644
--- a/nix2/driver.go
+++ b/nix2/driver.go
@@ -510,8 +510,8 @@ func (d *Driver) StartTask(cfg *drivers.TaskConfig) (*drivers.TaskHandle, *drive
 	}
 	// Use that repo for all packages not specified from a flake already.
 	for i := range driverConfig.Packages {
-		if !strings.Contains(driverConfig.Packages[i], "#") && !strings.Contains(driverConfig.Packages[i], "/") {
-			driverConfig.Packages[i] = nixpkgs + "#" + driverConfig.Packages[i]
+		if strings.HasPrefix(driverConfig.Packages[i], "#") {
+			driverConfig.Packages[i] = nixpkgs + driverConfig.Packages[i]
 		}
 	}
 
diff --git a/nix2/nix.go b/nix2/nix.go
index 5b94065..badf38c 100644
--- a/nix2/nix.go
+++ b/nix2/nix.go
@@ -25,7 +25,7 @@ func prepareNixPackages(taskDir string, packages []string, nixpkgs string) (hclu
 	mounts := make(hclutils.MapStrStr)
 
 	profileLink := filepath.Join(taskDir, "current-profile")
-	profile, err := nixBuildProfile(packages, profileLink)
+	profile, err := nixBuildProfile(taskDir, packages, profileLink)
 	if err != nil {
 		return nil, fmt.Errorf("Build of the flakes failed: %v", err)
 	}
@@ -71,7 +71,7 @@ func prepareNixPackages(taskDir string, packages []string, nixpkgs string) (hclu
 	return mounts, nil
 }
 
-func nixBuildProfile(flakes []string, link string) (string, error) {
+func nixBuildProfile(taskDir string, flakes []string, link string) (string, error) {
 	cmd := exec.Command("nix", append(
 		[]string{
 			"--extra-experimental-features", "nix-command",
@@ -84,6 +84,7 @@ func nixBuildProfile(flakes []string, link string) (string, error) {
 		flakes...)...)
 	stderr := &bytes.Buffer{}
 	cmd.Stderr = stderr
+	cmd.Dir = taskDir
 
 	if err := cmd.Run(); err != nil {
 		return "", fmt.Errorf("%v failed: %s. Err: %v", cmd.Args, stderr.String(), err)