feat(tvix/build): don't force outputs to be in store_dir r/7283

There's no need to require builds to also put their outputs in store_dir.

So rename store_dir to inputs_dir and make outputs consume paths, not
basenames.

Also document the possibility for builds to write to inputs_dir. Let's
see if we want to make this a constraint later.

Change-Id: Ib4df20afcdde2d771c269c422f04c7e95587cd0f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10447
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: flokli <flokli@flokli.de>

3 files changed, 73 insertions, 78 deletions

diff --git a/tvix/build-go/build.pb.go b/tvix/build-go/build.pb.go
index 8c65b04b7eff..fd387c1c3b96 100644
--- a/tvix/build-go/build.pb.go
+++ b/tvix/build-go/build.pb.go
@@ -64,8 +64,8 @@ type BuildRequest struct {
 	sizeCache     protoimpl.SizeCache
 	unknownFields protoimpl.UnknownFields
 
-	// The list of all root nodes that should be visible in STORE_DIR at the time
-	// of the build.
+	// The list of all root nodes that should be visible in `inputs_dir` at the
+	// time of the build.
 	// As root nodes are content-addressed, no additional signatures are needed
 	// to substitute / make these available in the build environment.
 	// Inputs are sorted by their names.
@@ -79,13 +79,14 @@ type BuildRequest struct {
 	WorkingDir string `protobuf:"bytes,3,opt,name=working_dir,json=workingDir,proto3" json:"working_dir,omitempty"`
 	// A list of "scratch" paths, relative to the build root.
 	// These will be write-able during the build.
-	// [build] in the case of Nix.
+	// [build, nix/store] in the case of Nix.
 	ScratchPaths []string `protobuf:"bytes,4,rep,name=scratch_paths,json=scratchPaths,proto3" json:"scratch_paths,omitempty"`
 	// The path where the castore input nodes will be located at,
 	// "/nix/store" in case of Nix.
-	StoreDir string `protobuf:"bytes,5,opt,name=store_dir,json=storeDir,proto3" json:"store_dir,omitempty"`
-	// The list of output nodes the build is expected to produce.
-	// These are basenames inside store_dir.
+	// Builds might also write into here (Nix builds do that).
+	InputsDir string `protobuf:"bytes,5,opt,name=inputs_dir,json=inputsDir,proto3" json:"inputs_dir,omitempty"`
+	// The list of output paths the build is expected to produce,
+	// relative to the root.
 	// If the path is not produced, the build is considered to have failed.
 	// Outputs are sorted.
 	Outputs []string `protobuf:"bytes,6,rep,name=outputs,proto3" json:"outputs,omitempty"`
@@ -165,9 +166,9 @@ func (x *BuildRequest) GetScratchPaths() []string {
 	return nil
 }
 
-func (x *BuildRequest) GetStoreDir() string {
+func (x *BuildRequest) GetInputsDir() string {
 	if x != nil {
-		return x.StoreDir
+		return x.InputsDir
 	}
 	return ""
 }
@@ -406,7 +407,7 @@ var file_tvix_build_protos_build_proto_rawDesc = []byte{
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@@ -416,47 +417,47 @@ var file_tvix_build_protos_build_proto_rawDesc = []byte{
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 }
 
 var (
diff --git a/tvix/build/protos/build.proto b/tvix/build/protos/build.proto
index bdabb037a080..e007ce968a7f 100644
--- a/tvix/build/protos/build.proto
+++ b/tvix/build/protos/build.proto
@@ -45,8 +45,8 @@ option go_package = "code.tvl.fyi/tvix/build-go;buildv1";
 // support "send all BuildRequest for a nixpkgs eval to a remote builder and put
 // the laptop to sleep" usecases later.
 message BuildRequest {
-  // The list of all root nodes that should be visible in STORE_DIR at the time
-  // of the build.
+  // The list of all root nodes that should be visible in `inputs_dir` at the
+  // time of the build.
   // As root nodes are content-addressed, no additional signatures are needed
   // to substitute / make these available in the build environment.
   // Inputs are sorted by their names.
@@ -63,15 +63,16 @@ message BuildRequest {
 
   // A list of "scratch" paths, relative to the build root.
   // These will be write-able during the build.
-  // [build] in the case of Nix.
+  // [build, nix/store] in the case of Nix.
   repeated string scratch_paths = 4;
 
   // The path where the castore input nodes will be located at,
   // "/nix/store" in case of Nix.
-  string store_dir = 5;
+  // Builds might also write into here (Nix builds do that).
+  string inputs_dir = 5;
 
-  // The list of output nodes the build is expected to produce.
-  // These are basenames inside store_dir.
+  // The list of output paths the build is expected to produce,
+  // relative to the root.
   // If the path is not produced, the build is considered to have failed.
   // Outputs are sorted.
   repeated string outputs = 6;
diff --git a/tvix/glue/src/tvix_build.rs b/tvix/glue/src/tvix_build.rs
index a0ebf49e1229..b647c7d40545 100644
--- a/tvix/glue/src/tvix_build.rs
+++ b/tvix/glue/src/tvix_build.rs
@@ -52,22 +52,15 @@ where
     command_args.push(derivation.builder.clone());
     command_args.extend_from_slice(&derivation.arguments);
 
-    // produce output_paths, which is the basename of each output (sorted)
-    // since Derivation is validated, we know output paths can be parsed.
-    // TODO: b/264 will remove the need to parse them here
-    let mut outputs: Vec<String> = derivation
+    // produce output_paths, which is the absolute path of each output (sorted)
+    let mut output_paths: Vec<String> = derivation
         .outputs
         .values()
-        .map(|output| {
-            let output_storepath = StorePathRef::from_absolute_path(output.path.as_bytes())
-                .expect("invalid output storepath");
-
-            output_storepath.to_string()
-        })
+        .map(|e| e.path[1..].to_owned())
         .collect();
 
     // Sort the outputs. We can use sort_unstable, as these are unique strings.
-    outputs.sort_unstable();
+    output_paths.sort_unstable();
 
     // Produce environment_vars. We use a BTreeMap while producing them, so the
     // resulting Vec is sorted by key.
@@ -151,13 +144,13 @@ where
 
     BuildRequest {
         command_args,
-        outputs,
+        outputs: output_paths,
         environment_vars,
         inputs,
+        inputs_dir: nix_compat::store_path::STORE_DIR.into(),
         constraints,
         working_dir: "build".into(),
-        scratch_paths: vec!["build".into()],
-        store_dir: nix_compat::store_path::STORE_DIR.into(),
+        scratch_paths: vec!["build".into(), "nix/store".into()],
     }
 }
 
@@ -245,10 +238,11 @@ mod test {
 
         assert_eq!(
             BuildRequest {
-                command_args: vec![":".to_string()],
-                outputs: vec!["fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo".to_string()],
+                command_args: vec![":".into()],
+                outputs: vec!["nix/store/fhaj6gmwns62s6ypkcldbaj2ybvkhx3p-foo".into()],
                 environment_vars: expected_environment_vars,
                 inputs: vec![INPUT_NODE_FOO.clone()],
+                inputs_dir: nix_compat::store_path::STORE_DIR.into(),
                 constraints: Some(BuildConstraints {
                     system: derivation.system.clone(),
                     min_memory: 0,
@@ -256,9 +250,8 @@ mod test {
                     available_ro_paths: vec![],
                     provide_bin_sh: true,
                 }),
-                working_dir: "build".to_string(),
-                scratch_paths: vec!["build".to_string()],
-                store_dir: nix_compat::store_path::STORE_DIR.to_string(),
+                working_dir: "build".into(),
+                scratch_paths: vec!["build".into(), "nix/store".into()],
             },
             build_request
         );
@@ -314,9 +307,10 @@ mod test {
         assert_eq!(
             BuildRequest {
                 command_args: vec![":".to_string()],
-                outputs: vec!["4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar".to_string()],
+                outputs: vec!["nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar".into()],
                 environment_vars: expected_environment_vars,
                 inputs: vec![],
+                inputs_dir: nix_compat::store_path::STORE_DIR.into(),
                 constraints: Some(BuildConstraints {
                     system: derivation.system.clone(),
                     min_memory: 0,
@@ -324,9 +318,8 @@ mod test {
                     available_ro_paths: vec![],
                     provide_bin_sh: true,
                 }),
-                working_dir: "build".to_string(),
-                scratch_paths: vec!["build".to_string()],
-                store_dir: nix_compat::store_path::STORE_DIR.to_string(),
+                working_dir: "build".into(),
+                scratch_paths: vec!["build".into(), "nix/store".into()],
             },
             build_request
         );