feat(tvix/nix-compat): input_derivations with StorePaths

...in `Derivation`.

This is more type-safe and should consume less memory.

This also removes some allocations in the potentially hot path of output hash calculation.

https: //b.tvl.fyi/issues/264
Change-Id: I6ad7d3cb868dc9f750894d449a6065608ef06e8c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10957
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: Peter Kolloch <info@eigenvalue.net>
Reviewed-by: Peter Kolloch <info@eigenvalue.net>

tvix/glue/src/builtins/derivation.rs

@@ -4,6 +4,7 @@ use crate::tvix_store_io::TvixStoreIO;
 use bstr::BString;
 use nix_compat::derivation::{Derivation, Output};
 use nix_compat::nixhash;
+use nix_compat::store_path::StorePath;
 use std::collections::{btree_map, BTreeSet};
 use std::rc::Rc;
 use tvix_eval::builtin_macros::builtins;
@@ -26,7 +27,23 @@ fn populate_inputs(drv: &mut Derivation, full_context: NixContext) {
                 drv.input_sources.insert(source.clone());
             }
 
-            NixContextElement::Single { name, derivation } => {
+            NixContextElement::Single {
+                name,
+                derivation: derivation_str,
+            } => {
+                // TODO: b/264
+                // We assume derivations to be passed validated, so ignoring rest
+                // and expecting parsing is ok.
+                let (derivation, _rest) =
+                    StorePath::from_absolute_path_full(derivation_str).expect("valid store path");
+
+                #[cfg(debug_assertions)]
+                assert!(
+                    _rest.iter().next().is_none(),
+                    "Extra path not empty for {}",
+                    derivation_str
+                );
+
                 match drv.input_derivations.entry(derivation.clone()) {
                     btree_map::Entry::Vacant(entry) => {
                         entry.insert(BTreeSet::from([name.clone()]));

tvix/glue/src/known_paths.rs

@@ -59,14 +59,8 @@ impl KnownPaths {
         // check input derivations to have been inserted.
         #[cfg(debug_assertions)]
         {
-            // TODO: b/264
+            for input_drv_path in drv.input_derivations.keys() {
-            // We assume derivations to be passed validated, so ignoring rest
+                debug_assert!(self.derivations.contains_key(input_drv_path));
-            // and expecting parsing is ok.
-            for input_drv_path_str in drv.input_derivations.keys() {
-                let (input_drv_path, _rest) =
-                    StorePath::from_absolute_path_full(input_drv_path_str)
-                        .expect("parse input drv path");
-                debug_assert!(self.derivations.contains_key(&input_drv_path));
             }
         }
 

tvix/glue/src/tvix_store_io.rs

@@ -140,17 +140,11 @@ impl TvixStoreIO {
                 let input_nodes: BTreeSet<Node> =
                     futures::stream::iter(drv.input_derivations.iter())
                         .map(|(input_drv_path, output_names)| {
-                            // since Derivation is validated, we know this can be parsed.
-                            let input_drv_path =
-                                StorePathRef::from_absolute_path(input_drv_path.as_bytes())
-                                    .expect("invalid drv path")
-                                    .to_owned();
-
                             // look up the derivation object
                             let input_drv = {
                                 let known_paths = self.known_paths.borrow();
                                 known_paths
-                                    .get_drv_by_drvpath(&input_drv_path)
+                                    .get_drv_by_drvpath(input_drv_path)
                                     .unwrap_or_else(|| panic!("{} not found", input_drv_path))
                                     .to_owned()
                             };

tvix/nix-compat/src/derivation/mod.rs

@@ -36,7 +36,7 @@ pub struct Derivation {
 
     /// Map from drv path to output names used from this derivation.
     #[serde(rename = "inputDrvs")]
-    pub input_derivations: BTreeMap<String, BTreeSet<String>>,
+    pub input_derivations: BTreeMap<StorePath, BTreeSet<String>>,
 
     /// Plain store paths of additional inputs.
     #[serde(rename = "inputSrcs")]
@@ -70,19 +70,7 @@ impl Derivation {
         write_outputs(writer, &self.outputs)?;
         write_char(writer, COMMA)?;
 
-        // To reproduce the exact hashes of original nix, we need to sort
+        write_input_derivations(writer, input_derivations)?;
-        // these by their aterm representation.
-        // StorePath has a different sort order, so we convert it here.
-        let input_derivations: BTreeMap<BString, &BTreeSet<String>> = input_derivations
-            .iter()
-            .map(|(k, v)| {
-                let mut aterm_k = Vec::new();
-                k.aterm_write(&mut aterm_k).expect("no write error to Vec");
-                (BString::new(aterm_k), v)
-            })
-            .collect();
-
-        write_input_derivations(writer, &input_derivations)?;
         write_char(writer, COMMA)?;
 
         write_input_sources(writer, &self.input_sources)?;
@@ -145,8 +133,11 @@ impl Derivation {
         // into a (sorted, guaranteed by BTreeSet) list of references
         let references: BTreeSet<String> = {
             let mut inputs = self.input_sources.clone();
-            let input_derivation_keys: Vec<String> =
+            let input_derivation_keys: Vec<String> = self
-                self.input_derivations.keys().cloned().collect();
+                .input_derivations
+                .keys()
+                .map(|k| k.to_absolute_path())
+                .collect();
             inputs.extend(input_derivation_keys);
             inputs
         };
@@ -211,12 +202,8 @@ impl Derivation {
             // derivation_or_fod_hash, and replace the derivation path with
             // it's HEXLOWER digest.
             let input_derivations = BTreeMap::from_iter(self.input_derivations.iter().map(
-                |(drv_path_str, output_names)| {
+                |(drv_path, output_names)| {
-                    // parse drv_path to StorePathRef
+                    let hash = fn_get_derivation_or_fod_hash(&drv_path.into());
-                    let drv_path = StorePathRef::from_absolute_path(drv_path_str.as_bytes())
-                        .expect("invalid input derivation path");
-
-                    let hash = fn_get_derivation_or_fod_hash(&drv_path);
 
                     (hash, output_names.to_owned())
                 },

tvix/nix-compat/src/derivation/parser.rs

@@ -14,6 +14,7 @@ use thiserror;
 
 use crate::derivation::parse_error::{into_nomerror, ErrorKind, NomError, NomResult};
 use crate::derivation::{write, CAHash, Derivation, Output};
+use crate::store_path::{self, StorePath, StorePathRef};
 use crate::{aterm, nixhash};
 
 #[derive(Debug, thiserror::Error)]
@@ -142,11 +143,11 @@ fn parse_outputs(i: &[u8]) -> NomResult<&[u8], BTreeMap<String, Output>> {
     }
 }
 
-fn parse_input_derivations(i: &[u8]) -> NomResult<&[u8], BTreeMap<String, BTreeSet<String>>> {
+fn parse_input_derivations(i: &[u8]) -> NomResult<&[u8], BTreeMap<StorePath, BTreeSet<String>>> {
     let (i, input_derivations_list) = parse_kv::<Vec<String>, _>(aterm::parse_str_list)(i)?;
 
     // This is a HashMap of drv paths to a list of output names.
-    let mut input_derivations: BTreeMap<String, BTreeSet<String>> = BTreeMap::new();
+    let mut input_derivations: BTreeMap<StorePath, BTreeSet<String>> = BTreeMap::new();
 
     for (input_derivation, output_names) in input_derivations_list {
         let mut new_output_names = BTreeSet::new();
@@ -159,10 +160,26 @@ fn parse_input_derivations(i: &[u8]) -> NomResult<&[u8], BTreeMap<String, BTreeS
                         output_name.to_string(),
                     ),
                 }));
-            } else {
-                new_output_names.insert(output_name);
             }
+            new_output_names.insert(output_name);
         }
+
+        #[cfg(debug_assertions)]
+        let input_derivation_str = input_derivation.clone();
+
+        let input_derivation: StorePath =
+            StorePathRef::from_absolute_path(input_derivation.as_bytes())
+                .map_err(|e: store_path::Error| {
+                    nom::Err::Failure(NomError {
+                        input: i,
+                        code: e.into(),
+                    })
+                })?
+                .to_owned();
+
+        #[cfg(debug_assertions)]
+        assert_eq!(input_derivation_str, input_derivation.to_absolute_path());
+
         input_derivations.insert(input_derivation, new_output_names);
     }
 
@@ -297,8 +314,11 @@ where
 mod tests {
     use std::collections::{BTreeMap, BTreeSet};
 
-    use crate::derivation::{
+    use crate::{
-        parse_error::ErrorKind, parser::from_algo_and_mode_and_digest, CAHash, NixHash, Output,
+        derivation::{
+            parse_error::ErrorKind, parser::from_algo_and_mode_and_digest, CAHash, NixHash, Output,
+        },
+        store_path::StorePath,
     };
     use bstr::{BString, ByteSlice};
     use hex_literal::hex;
@@ -334,10 +354,11 @@ mod tests {
             b.insert("b".to_string(), b"2".as_bstr().to_owned());
             b
         };
-        static ref EXP_INPUT_DERIVATIONS_SIMPLE: BTreeMap<String, BTreeSet<String>> = {
+        static ref EXP_INPUT_DERIVATIONS_SIMPLE: BTreeMap<StorePath, BTreeSet<String>> = {
             let mut b = BTreeMap::new();
             b.insert(
-                "/nix/store/8bjm87p310sb7r2r0sg4xrynlvg86j8k-hello-2.12.1.tar.gz.drv".to_string(),
+                StorePath::from_bytes(b"8bjm87p310sb7r2r0sg4xrynlvg86j8k-hello-2.12.1.tar.gz.drv")
+                    .unwrap(),
                 {
                     let mut output_names = BTreeSet::new();
                     output_names.insert("out".to_string());
@@ -345,7 +366,8 @@ mod tests {
                 },
             );
             b.insert(
-                "/nix/store/p3jc8aw45dza6h52v81j7lk69khckmcj-bash-5.2-p15.drv".to_string(),
+                StorePath::from_bytes(b"p3jc8aw45dza6h52v81j7lk69khckmcj-bash-5.2-p15.drv")
+                    .unwrap(),
                 {
                     let mut output_names = BTreeSet::new();
                     output_names.insert("out".to_string());
@@ -400,7 +422,7 @@ mod tests {
     #[test_case(EXP_INPUT_DERIVATIONS_SIMPLE_ATERM.as_bytes(), &EXP_INPUT_DERIVATIONS_SIMPLE; "simple")]
     fn parse_input_derivations(
         input: &'static [u8],
-        expected: &BTreeMap<String, BTreeSet<String>>,
+        expected: &BTreeMap<StorePath, BTreeSet<String>>,
     ) {
         let (rest, parsed) = super::parse_input_derivations(input).expect("must parse");
 

tvix/nix-compat/src/derivation/tests/mod.rs

@@ -104,7 +104,7 @@ fn from_aterm_bytes(path_to_drv_file: &str) {
 
     assert_eq!(
         &aterm_bytes,
-        &parsed_drv.to_aterm_bytes(),
+        &BString::new(parsed_drv.to_aterm_bytes()),
         "expected serialized ATerm to match initial input"
     );
 }
@@ -381,10 +381,9 @@ fn output_path_construction() {
     );
 
     // assemble foo input_derivations
-    foo_drv.input_derivations.insert(
+    foo_drv
-        bar_drv_path.to_absolute_path(),
+        .input_derivations
-        BTreeSet::from(["out".to_string()]),
+        .insert(bar_drv_path, BTreeSet::from(["out".to_string()]));
-    );
 
     // calculate foo output paths
     let foo_calc_result = foo_drv.calculate_output_paths(

tvix/nix-compat/src/derivation/validate.rs

@@ -53,14 +53,7 @@ impl Derivation {
         // Validate all input_derivations
         for (input_derivation_path, output_names) in &self.input_derivations {
             // Validate input_derivation_path
-            if let Err(e) = StorePathRef::from_absolute_path(input_derivation_path.as_bytes()) {
+            if !input_derivation_path.name().ends_with(".drv") {
-                return Err(DerivationError::InvalidInputDerivationPath(
-                    input_derivation_path.to_string(),
-                    e,
-                ));
-            }
-
-            if !input_derivation_path.ends_with(".drv") {
                 return Err(DerivationError::InvalidInputDerivationPrefix(
                     input_derivation_path.to_string(),
                 ));

tvix/nix-compat/src/derivation/write.rs

@@ -149,7 +149,7 @@ pub(crate) fn write_outputs(
 
 pub(crate) fn write_input_derivations(
     writer: &mut impl Write,
-    input_derivations: &BTreeMap<BString, &BTreeSet<String>>,
+    input_derivations: &BTreeMap<impl AtermWriteable, BTreeSet<String>>,
 ) -> Result<(), io::Error> {
     write_char(writer, BRACKET_OPEN)?;
 
@@ -159,7 +159,7 @@ pub(crate) fn write_input_derivations(
         }
 
         write_char(writer, PAREN_OPEN)?;
-        writer.write_all(input_derivation_aterm)?;
+        input_derivation_aterm.aterm_write(writer)?;
         write_char(writer, COMMA)?;
 
         write_char(writer, BRACKET_OPEN)?;

tvix/nix-compat/src/store_path/mod.rs

@@ -75,9 +75,26 @@ impl PartialOrd for StorePath {
     }
 }
 
+/// `StorePath`s are sorted by their reverse digest to match the sorting order
+/// of the nixbase32-encoded string.
 impl Ord for StorePath {
     fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-        self.digest.cmp(&other.digest)
+        let order = self.digest.iter().rev().cmp(other.digest.iter().rev());
+
+        // This order must match the order of the nixbase32 encoded digests.
+        #[cfg(debug_assertions)]
+        {
+            let self_hash = nixbase32::encode(&self.digest);
+            let other_hash = nixbase32::encode(&other.digest);
+            let canonical_order = self_hash.cmp(&other_hash);
+            assert_eq!(
+                order, canonical_order,
+                "Ordering of nixbase32 differs, {:?} instead of {:?}:\n{:?}\n{:?}",
+                order, canonical_order, self_hash, other_hash
+            );
+        }
+
+        order
     }
 }
 
@@ -339,10 +356,12 @@ impl fmt::Display for StorePathRef<'_> {
 
 #[cfg(test)]
 mod tests {
+    use std::cmp::Ordering;
     use std::path::PathBuf;
 
     use crate::store_path::{StorePathRef, DIGEST_SIZE};
     use hex_literal::hex;
+    use pretty_assertions::assert_eq;
     use test_case::test_case;
 
     use super::{Error, StorePath};
@@ -362,6 +381,47 @@ mod tests {
         assert_eq!(example_nix_path_str, nixpath.to_string())
     }
 
+    #[test]
+    fn store_path_ordering() {
+        let store_paths = [
+            "/nix/store/0lk5dgi01r933abzfj9c9wlndg82yd3g-psutil-5.9.6.tar.gz.drv",
+            "/nix/store/1xj43bva89f9qmwm37zl7r3d7m67i9ck-shorttoc-1.3-tex.drv",
+            "/nix/store/2gb633czchi20jq1kqv70rx2yvvgins8-lifted-base-0.2.3.12.tar.gz.drv",
+            "/nix/store/2vksym3r3zqhp15q3fpvw2mnvffv11b9-docbook-xml-4.5.zip.drv",
+            "/nix/store/5q918awszjcz5720xvpc2czbg1sdqsf0-rust_renaming-0.1.0-lib",
+            "/nix/store/7jw30i342sr2p1fmz5xcfnch65h4zbd9-dbus-1.14.10.tar.xz.drv",
+            "/nix/store/96yqwqhnp3qya4rf4n0rcl0lwvrylp6k-eap8021x-222.40.1.tar.gz.drv",
+            "/nix/store/9gjqg36a1v0axyprbya1hkaylmnffixg-virtualenv-20.24.5.tar.gz.drv",
+            "/nix/store/a4i5mci2g9ada6ff7ks38g11dg6iqyb8-perl-5.32.1.drv",
+            "/nix/store/a5g76ljava4h5pxlggz3aqdhs3a4fk6p-ToolchainInfo.plist.drv",
+            "/nix/store/db46l7d6nswgz4ffp1mmd56vjf9g51v6-version.plist.drv",
+            "/nix/store/g6f7w20sd7vwy0rc1r4bfsw4ciclrm4q-crates-io-num_cpus-1.12.0.drv",
+            "/nix/store/iw82n1wwssb8g6772yddn8c3vafgv9np-bootstrap-stage1-sysctl-stdenv-darwin.drv",
+            "/nix/store/lp78d1y5wxpcn32d5c4r7xgbjwiw0cgf-logo.svg.drv",
+            "/nix/store/mf00ank13scv1f9l1zypqdpaawjhfr3s-python3.11-psutil-5.9.6.drv",
+            "/nix/store/mpfml61ra7pz90124jx9r3av0kvkz2w1-perl5.36.0-Encode-Locale-1.05",
+            "/nix/store/qhsvwx4h87skk7c4mx0xljgiy3z93i23-source.drv",
+            "/nix/store/riv7d73adim8hq7i04pr8kd0jnj93nav-fdk-aac-2.0.2.tar.gz.drv",
+            "/nix/store/s64b9031wga7vmpvgk16xwxjr0z9ln65-human-signals-5.0.0.tgz-extracted",
+            "/nix/store/w6svg3m2xdh6dhx0gl1nwa48g57d3hxh-thiserror-1.0.49",
+        ];
+
+        for w in store_paths.windows(2) {
+            if w.len() < 2 {
+                continue;
+            }
+            let (pa, _) = StorePath::from_absolute_path_full(w[0]).expect("parseable");
+            let (pb, _) = StorePath::from_absolute_path_full(w[1]).expect("parseable");
+            assert_eq!(
+                Ordering::Less,
+                pa.cmp(&pb),
+                "{:?} not less than {:?}",
+                w[0],
+                w[1]
+            );
+        }
+    }
+
     /// This is the store path rejected when `nix-store --add`'ing an
     /// empty `.gitignore` file.
     ///
@@ -440,10 +500,10 @@ mod tests {
 
     #[test]
     fn serialize_ref() {
-        let store_path_str =
+        let nixpath_actual = StorePathRef::from_bytes(
-            "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432";
+            b"00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432",
-        let nixpath_actual =
+        )
-            StorePathRef::from_absolute_path(store_path_str.as_bytes()).expect("can parse");
+        .expect("can parse");
 
         let serialized = serde_json::to_string(&nixpath_actual).expect("can serialize");
 
@@ -455,11 +515,10 @@ mod tests {
 
     #[test]
     fn serialize_owned() {
-        let store_path_str =
+        let nixpath_actual = StorePath::from_bytes(
-            "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432";
+            b"00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432",
-        let nixpath_actual = StorePathRef::from_absolute_path(store_path_str.as_bytes())
+        )
-            .expect("can parse")
+        .expect("can parse");
-            .to_owned();
 
         let serialized = serde_json::to_string(&nixpath_actual).expect("can serialize");