From 70712d466fd52ebd48c5ddda2556ac36f04677a0 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Isma=C3=ABl=20Bouya?= <ismael.bouya@normalesup.org>
Date: Sat, 24 Oct 2020 10:49:21 +0200
Subject: [PATCH] Add dry-run patch for morph

---
 nixops/Makefile              |  3 ++
 overlays/morph/default.nix   |  2 +-
 overlays/morph/dry-run.patch | 59 ++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 overlays/morph/dry-run.patch

diff --git a/nixops/Makefile b/nixops/Makefile
index 0bebaf8..cefd677 100644
--- a/nixops/Makefile
+++ b/nixops/Makefile
@@ -46,6 +46,9 @@ debug:
 build:
 	./scripts/with_env morph build default.nix $(MORPH_ARGS)
 
+dry-run:
+	./scripts/with_env morph build --dry-run default.nix $(MORPH_ARGS)
+
 upload:
 	./scripts/with_env morph push default.nix $(MORPH_ARGS)
 
diff --git a/overlays/morph/default.nix b/overlays/morph/default.nix
index ee59e25..448f051 100644
--- a/overlays/morph/default.nix
+++ b/overlays/morph/default.nix
@@ -1,5 +1,5 @@
 self: super: {
   morph = super.morph.overrideAttrs(old: {
-    patches = (old.patches or []) ++ [ ./verbose_nix.patch ];
+    patches = (old.patches or []) ++ [ ./verbose_nix.patch ./dry-run.patch ];
   });
 }
diff --git a/overlays/morph/dry-run.patch b/overlays/morph/dry-run.patch
new file mode 100644
index 0000000..2ff099e
--- /dev/null
+++ b/overlays/morph/dry-run.patch
@@ -0,0 +1,59 @@
+diff --git a/morph.go b/morph.go
+index a88414b..e5894df 100644
+--- a/morph.go
++++ b/morph.go
+@@ -542,6 +542,7 @@ func getNixContext() *nix.NixContext {
+ 	return &nix.NixContext{
+ 		EvalMachines:    filepath.Join(assetRoot, assets.Friendly, "eval-machines.nix"),
+ 		ShowTrace:       showTrace,
++		DryRun:          *dryRun,
+ 		KeepGCRoot:      *keepGCRoot,
+ 		AllowBuildShell: *allowBuildShell,
+ 	}
+@@ -574,8 +575,10 @@ func buildHosts(hosts []nix.Host) (resultPath string, err error) {
+ 		return
+ 	}
+ 
+-	fmt.Fprintln(os.Stderr, "nix result path: ")
+-	fmt.Println(resultPath)
++	if resultPath != "" {
++		fmt.Fprintln(os.Stderr, "nix result path: ")
++		fmt.Println(resultPath)
++	}
+ 	return
+ }
+ 
+diff --git a/nix/nix.go b/nix/nix.go
+index 6a9cfd5..0f7884b 100644
+--- a/nix/nix.go
++++ b/nix/nix.go
+@@ -49,6 +49,7 @@ type Deployment struct {
+ type NixContext struct {
+ 	EvalMachines    string
+ 	ShowTrace       bool
++	DryRun          bool
+ 	KeepGCRoot      bool
+ 	AllowBuildShell bool
+ }
+@@ -269,6 +270,10 @@ func (ctx *NixContext) BuildMachines(deploymentPath string, hosts []Host, nixArg
+ 		args = append(args, "--show-trace")
+ 	}
+ 
++	if ctx.DryRun {
++		args = append(args, "--dry-run")
++	}
++
+ 	if nixBuildTargets != "" {
+ 		args = append(args,
+ 			"--arg", "buildTargets", nixBuildTargets)
+@@ -308,6 +313,10 @@ func (ctx *NixContext) BuildMachines(deploymentPath string, hosts []Host, nixArg
+ 		return resultPath, errors.New(errorMessage)
+ 	}
+ 
++	if ctx.DryRun {
++		return "", err
++	}
++
+ 	resultPath, err = os.Readlink(resultLinkPath)
+ 	if err != nil {
+ 		return "", err
-- 
2.41.0