feat(tvix/glue): contextful derivation r/7338

We calculate the input context by performing the union of context
over all input of the derivation.

Then, we just pass the rest of it to the remaining machinery.

Finally, we re-emit an `outPath` and a `drvPath` containing the expected
contexts.

Change-Id: I74905fb258b5bee8b08d1208c9eb87f51b92a890
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10436
Autosubmit: raitobezarius <tvl@lahfa.xyz>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

1 files changed, 63 insertions, 64 deletions

diff --git a/tvix/glue/src/builtins/derivation.rs b/tvix/glue/src/builtins/derivation.rs
index 95314f4b9dc9..517ea0032180 100644
--- a/tvix/glue/src/builtins/derivation.rs
+++ b/tvix/glue/src/builtins/derivation.rs
@@ -1,6 +1,6 @@
 //! Implements `builtins.derivation`, the core of what makes Nix build packages.
 use crate::builtins::DerivationError;
-use crate::known_paths::{KnownPaths, PathKind, PathName};
+use crate::known_paths::KnownPaths;
 use nix_compat::derivation::{Derivation, Output};
 use nix_compat::nixhash;
 use std::cell::RefCell;
@@ -9,7 +9,8 @@ use std::rc::Rc;
 use tvix_eval::builtin_macros::builtins;
 use tvix_eval::generators::{self, emit_warning_kind, GenCo};
 use tvix_eval::{
-    AddContext, CatchableErrorKind, CoercionKind, ErrorKind, NixAttrs, NixList, Value, WarningKind,
+    AddContext, CatchableErrorKind, CoercionKind, ErrorKind, NixAttrs, NixContext,
+    NixContextElement, NixList, Value, WarningKind,
 };
 
 // Constants used for strangely named fields in derivation inputs.
@@ -46,20 +47,15 @@ async fn populate_outputs(
 }
 
 /// Populate the inputs of a derivation from the build references
-/// found when scanning the derivation's parameters.
-fn populate_inputs<I: IntoIterator<Item = PathName>>(
-    drv: &mut Derivation,
-    known_paths: &KnownPaths,
-    references: I,
-) {
-    for reference in references.into_iter() {
-        let reference = &known_paths[&reference];
-        match &reference.kind {
-            PathKind::Plain => {
-                drv.input_sources.insert(reference.path.clone());
+/// found when scanning the derivation's parameters and extracting their contexts.
+fn populate_inputs(drv: &mut Derivation, full_context: NixContext) {
+    for element in full_context.iter() {
+        match element {
+            NixContextElement::Plain(source) => {
+                drv.input_sources.insert(source.clone());
             }
 
-            PathKind::Output { name, derivation } => {
+            NixContextElement::Single { name, derivation } => {
                 match drv.input_derivations.entry(derivation.clone()) {
                     btree_map::Entry::Vacant(entry) => {
                         entry.insert(BTreeSet::from([name.clone()]));
@@ -71,16 +67,12 @@ fn populate_inputs<I: IntoIterator<Item = PathName>>(
                 }
             }
 
-            PathKind::Derivation { output_names } => {
-                match drv.input_derivations.entry(reference.path.clone()) {
-                    btree_map::Entry::Vacant(entry) => {
-                        entry.insert(output_names.clone());
-                    }
-
-                    btree_map::Entry::Occupied(mut entry) => {
-                        entry.get_mut().extend(output_names.clone().into_iter());
-                    }
-                }
+            NixContextElement::Derivation(_drv_path) => {
+                // This is a hard one, it means that
+                // we are depending on a drvPath of ourselves
+                // *or* another derivation's drvPath.
+                // What to do here?
+                panic!("please do not depend on drvPath, I have 2 hours of sleep in blood");
             }
         }
     }
@@ -232,6 +224,7 @@ pub(crate) mod derivation_builtins {
     use super::*;
     use nix_compat::store_path::hash_placeholder;
     use tvix_eval::generators::Gen;
+    use tvix_eval::{NixContext, NixContextElement, NixString};
 
     #[builtin("placeholder")]
     async fn builtin_placeholder(co: GenCo, input: Value) -> Result<Value, ErrorKind> {
@@ -299,15 +292,31 @@ pub(crate) mod derivation_builtins {
             Ok(Ok(None))
         }
 
+        let mut input_context = NixContext::new();
+
         for (name, value) in input.clone().into_iter_sorted() {
             let value = generators::request_force(&co, value).await;
             if ignore_nulls && matches!(value, Value::Null) {
                 continue;
             }
 
-            match strong_importing_coerce_to_string(&co, value.clone()).await? {
+            match generators::request_string_coerce(
+                &co,
+                value.clone(),
+                CoercionKind {
+                    strong: true,
+                    import_paths: true,
+                },
+            )
+            .await
+            {
                 Err(cek) => return Ok(Value::Catchable(cek)),
                 Ok(val_str) => {
+                    // Learn about this derivation references
+                    // by looking at its context.
+                    input_context.mimic(&val_str);
+
+                    let val_str = val_str.as_str().to_string();
                     // handle_derivation_parameters tells us whether the
                     // argument should be added to the environment; continue
                     // to the next one otherwise
@@ -370,21 +379,6 @@ pub(crate) mod derivation_builtins {
             }
         }
 
-        // Scan references in relevant attributes to detect any build-references.
-        let references = {
-            let state = state.borrow();
-            if state.is_empty() {
-                // skip reference scanning, create an empty result
-                Default::default()
-            } else {
-                let mut refscan = state.reference_scanner();
-                drv.arguments.iter().for_each(|s| refscan.scan(s));
-                drv.environment.values().for_each(|s| refscan.scan(s));
-                refscan.scan(&drv.builder);
-                refscan.finalise()
-            }
-        };
-
         // Each output name needs to exist in the environment, at this
         // point initialised as an empty string because that is the
         // way of Golang ;)
@@ -398,8 +392,8 @@ pub(crate) mod derivation_builtins {
             }
         }
 
+        populate_inputs(&mut drv, input_context);
         let mut known_paths = state.borrow_mut();
-        populate_inputs(&mut drv, &known_paths, references);
 
         // At this point, derivation fields are fully populated from
         // eval data structures.
@@ -428,25 +422,35 @@ pub(crate) mod derivation_builtins {
             &derivation_or_fod_hash_final,
         );
 
-        // mark all the new paths as known
-        let output_names: Vec<String> = drv.outputs.keys().map(Clone::clone).collect();
-        known_paths.drv(derivation_path.to_absolute_path(), &output_names);
-
-        for (output_name, output) in &drv.outputs {
-            known_paths.output(
-                &output.path,
-                output_name,
-                derivation_path.to_absolute_path(),
-            );
-        }
-
-        let mut new_attrs: Vec<(String, String)> = drv
+        let mut new_attrs: Vec<(String, NixString)> = drv
             .outputs
             .into_iter()
-            .map(|(name, output)| (name, output.path))
+            .map(|(name, output)| {
+                (
+                    name.clone(),
+                    (
+                        output.path,
+                        Some(
+                            NixContextElement::Single {
+                                name,
+                                derivation: derivation_path.to_absolute_path(),
+                            }
+                            .into(),
+                        ),
+                    )
+                        .into(),
+                )
+            })
             .collect();
 
-        new_attrs.push(("drvPath".to_string(), derivation_path.to_absolute_path()));
+        new_attrs.push((
+            "drvPath".to_string(),
+            (
+                derivation_path.to_absolute_path(),
+                Some(NixContextElement::Derivation(derivation_path.to_absolute_path()).into()),
+            )
+                .into(),
+        ));
 
         Ok(Value::Attrs(Box::new(NixAttrs::from_iter(
             new_attrs.into_iter(),
@@ -454,12 +458,7 @@ pub(crate) mod derivation_builtins {
     }
 
     #[builtin("toFile")]
-    async fn builtin_to_file(
-        state: Rc<RefCell<KnownPaths>>,
-        co: GenCo,
-        name: Value,
-        content: Value,
-    ) -> Result<Value, ErrorKind> {
+    async fn builtin_to_file(co: GenCo, name: Value, content: Value) -> Result<Value, ErrorKind> {
         let name = name
             .to_str()
             .context("evaluating the `name` parameter of builtins.toFile")?;
@@ -482,11 +481,11 @@ pub(crate) mod derivation_builtins {
         .map_err(DerivationError::InvalidDerivation)?
         .to_absolute_path();
 
-        state.borrow_mut().plain(&path);
+        let context: NixContext = NixContextElement::Plain(path.clone()).into();
 
         // TODO: actually persist the file in the store at that path ...
 
-        Ok(Value::String(path.into()))
+        Ok(Value::String(NixString::new_context_from(context, &path)))
     }
 }