feat(nix-compat/{aterm,derivation}): init parser r/6831

This provides a nom-based parser for Nix derivations in ATerm format,
which can be reached via `Derivation::from_aterm_bytes`.

Some of the lower-level ATerm primitives are moved into a (new) aterm
module, and some more higher-level ones that construct derivation-
specific types.

Also, move the escape_bytes function into there, this is a generic ATerm
thing.

Change-Id: I2b03b8a1461c7ea2fcb8640c2fc3d1fa3ea719fb
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9730
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI

1 files changed, 327 insertions, 0 deletions

diff --git a/tvix/nix-compat/src/derivation/parser.rs b/tvix/nix-compat/src/derivation/parser.rs
new file mode 100644
index 0000000000..dfcd327e4f
--- /dev/null
+++ b/tvix/nix-compat/src/derivation/parser.rs
@@ -0,0 +1,327 @@
+//! This module constructs a [Derivation] by parsing its [ATerm][]
+//! serialization.
+//!
+//! [ATerm]: http://program-transformation.org/Tools/ATermFormat.html
+
+use bstr::BString;
+use nom::bytes::complete::tag;
+use nom::character::complete::char as nomchar;
+use nom::combinator::{all_consuming, map_res};
+use nom::multi::{separated_list0, separated_list1};
+use nom::sequence::{delimited, preceded, separated_pair, terminated, tuple};
+use std::collections::{BTreeMap, BTreeSet};
+use thiserror;
+
+use super::parse_error::{into_nomerror, ErrorKind, NomError, NomResult};
+use super::{write, Derivation, NixHashWithMode, Output};
+use crate::{aterm, nixhash};
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error<I> {
+    #[error("parsing error: {0}")]
+    ParseError(NomError<I>),
+    #[error("premature EOF")]
+    Incomplete,
+    #[error("validation error: {0}")]
+    ValidationError(super::DerivationError),
+}
+
+pub(crate) fn parse(i: &[u8]) -> Result<Derivation, Error<&[u8]>> {
+    match all_consuming(parse_derivation)(i) {
+        Ok((rest, derivation)) => {
+            // this shouldn't happen, as all_consuming shouldn't return.
+            debug_assert!(rest.is_empty());
+
+            // invoke validate
+            derivation.validate(true).map_err(Error::ValidationError)?;
+
+            Ok(derivation)
+        }
+        Err(nom::Err::Incomplete(_)) => Err(Error::Incomplete),
+        Err(nom::Err::Error(e) | nom::Err::Failure(e)) => Err(Error::ParseError(e)),
+    }
+}
+
+/// Parse one output in ATerm. This is 4 string fields inside parans:
+/// output name, output path, algo (and mode), digest.
+/// Returns the output name and [Output] struct.
+fn parse_output(i: &[u8]) -> NomResult<&[u8], (String, Output)> {
+    delimited(
+        nomchar('('),
+        map_res(
+            |i| {
+                tuple((
+                    terminated(aterm::parse_string_field, nomchar(',')),
+                    terminated(aterm::parse_string_field, nomchar(',')),
+                    terminated(aterm::parse_string_field, nomchar(',')),
+                    aterm::parse_bstr_field,
+                ))(i)
+                .map_err(into_nomerror)
+            },
+            |(output_name, output_path, algo_and_mode, encoded_digest)| {
+                // convert these 4 fields into an [Output].
+                let hash_with_mode_res = {
+                    if algo_and_mode.is_empty() && encoded_digest.is_empty() {
+                        None
+                    } else {
+                        match data_encoding::HEXLOWER.decode(&encoded_digest) {
+                            Ok(digest) => Some(NixHashWithMode::from_algo_mode_hash(
+                                &algo_and_mode,
+                                &digest,
+                            )),
+                            Err(e) => Some(Err(nixhash::Error::InvalidBase64Encoding(e))),
+                        }
+                    }
+                }
+                .transpose();
+
+                match hash_with_mode_res {
+                    Ok(hash_with_mode) => Ok((
+                        output_name,
+                        Output {
+                            path: output_path,
+                            hash_with_mode,
+                        },
+                    )),
+                    Err(e) => Err(nom::Err::Failure(NomError {
+                        input: i,
+                        code: ErrorKind::NixHashError(e),
+                    })),
+                }
+            },
+        ),
+        nomchar(')'),
+    )(i)
+}
+
+/// Parse multiple outputs in ATerm. This is a list of things acccepted by
+/// parse_output, and takes care of turning the (String, Output) returned from
+/// it to a BTreeMap.
+/// We don't use parse_kv here, as it's dealing with 2-tuples, and these are
+/// 4-tuples.
+fn parse_outputs(i: &[u8]) -> NomResult<&[u8], BTreeMap<String, Output>> {
+    let res = delimited(
+        nomchar('['),
+        separated_list1(tag(","), parse_output),
+        nomchar(']'),
+    )(i);
+
+    match res {
+        Ok((rst, outputs_lst)) => {
+            let mut outputs: BTreeMap<String, Output> = BTreeMap::default();
+            for (output_name, output) in outputs_lst.into_iter() {
+                if outputs.contains_key(&output_name) {
+                    return Err(nom::Err::Failure(NomError {
+                        input: i,
+                        code: ErrorKind::DuplicateMapKey(output_name),
+                    }));
+                }
+                outputs.insert(output_name, output);
+            }
+            Ok((rst, outputs))
+        }
+        // pass regular parse errors along
+        Err(e) => Err(e),
+    }
+}
+
+fn parse_input_derivations(i: &[u8]) -> NomResult<&[u8], BTreeMap<String, Vec<String>>> {
+    parse_kv::<Vec<String>, _>(aterm::parse_str_list)(i)
+}
+
+pub fn parse_derivation(i: &[u8]) -> NomResult<&[u8], Derivation> {
+    use nom::Parser;
+    preceded(
+        tag(write::DERIVATION_PREFIX),
+        delimited(
+            // inside parens
+            nomchar('('),
+            // tuple requires all errors to be of the same type, so we need to be a
+            // bit verbose here wrapping generic IResult into [NomATermResult].
+            tuple((
+                // parse outputs
+                terminated(parse_outputs, nomchar(',')),
+                // // parse input derivations
+                terminated(parse_input_derivations, nomchar(',')),
+                // // parse input sources
+                |i| terminated(aterm::parse_str_list, nomchar(','))(i).map_err(into_nomerror),
+                // // parse system
+                |i| terminated(aterm::parse_string_field, nomchar(','))(i).map_err(into_nomerror),
+                // // parse builder
+                |i| terminated(aterm::parse_string_field, nomchar(','))(i).map_err(into_nomerror),
+                // // parse arguments
+                |i| terminated(aterm::parse_str_list, nomchar(','))(i).map_err(into_nomerror),
+                // parse environment
+                parse_kv::<BString, _>(aterm::parse_bstr_field),
+            )),
+            nomchar(')'),
+        )
+        .map(
+            |(
+                outputs,
+                input_derivations,
+                input_sources,
+                system,
+                builder,
+                arguments,
+                environment,
+            )| {
+                // All values in input_derivations need to be converted from
+                // Vec<String> to BTreeSet<String>
+                let mut input_derivations_new: BTreeMap<_, BTreeSet<_>> = BTreeMap::new();
+                for (k, v) in input_derivations.into_iter() {
+                    let values_new: BTreeSet<_> = BTreeSet::from_iter(v.into_iter());
+                    input_derivations_new.insert(k, values_new);
+                    // TODO: actually check they're not duplicate in the parser side!
+                }
+
+                // Input sources need to be converted from Vec<_> to BTreeSet<_>
+                let input_sources_new: BTreeSet<_> = BTreeSet::from_iter(input_sources);
+
+                Derivation {
+                    arguments,
+                    builder,
+                    environment,
+                    input_derivations: input_derivations_new,
+                    input_sources: input_sources_new,
+                    outputs,
+                    system,
+                }
+            },
+        ),
+    )(i)
+}
+
+/// Parse a list of key/value pairs into a BTreeMap.
+/// The parser for the values can be passed in.
+/// In terms of ATerm, this is just a 2-tuple,
+/// but we have the additional restriction that the first element needs to be
+/// unique across all tuples.
+pub(crate) fn parse_kv<'a, V, VF>(
+    vf: VF,
+) -> impl FnMut(&'a [u8]) -> NomResult<&'a [u8], BTreeMap<String, V>> + 'static
+where
+    VF: FnMut(&'a [u8]) -> nom::IResult<&'a [u8], V, nom::error::Error<&'a [u8]>> + Clone + 'static,
+{
+    move |i|
+    // inside brackets
+    delimited(
+        nomchar('['),
+        |ii| {
+            let res = separated_list0(
+                nomchar(','),
+                // inside parens
+                delimited(
+                    nomchar('('),
+                    separated_pair(
+                        aterm::parse_string_field,
+                        nomchar(','),
+                        vf.clone(),
+                    ),
+                    nomchar(')'),
+                ),
+            )(ii).map_err(into_nomerror);
+
+            match res {
+                Ok((rest, pairs)) => {
+                    let mut kvs: BTreeMap<String, V> = BTreeMap::new();
+                    for (k, v) in pairs.into_iter() {
+                        // collect the 2-tuple to a BTreeMap,
+                        // and fail if the key was already seen before.
+                        if kvs.insert(k.clone(), v).is_some() {
+                            return Err(nom::Err::Failure(NomError {
+                                input: i,
+                                code: ErrorKind::DuplicateMapKey(k),
+                            }));
+                        }
+                    }
+                    Ok((rest, kvs))
+                }
+                Err(e) => Err(e),
+            }
+        },
+        nomchar(']'),
+    )(i)
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::BTreeMap;
+
+    use crate::derivation::Output;
+    use bstr::{BString, ByteSlice};
+    use lazy_static::lazy_static;
+    use test_case::test_case;
+
+    lazy_static! {
+        static ref EXP_MULTI_OUTPUTS: BTreeMap<String, Output> = {
+            let mut b = BTreeMap::new();
+            b.insert(
+                "lib".to_string(),
+                Output {
+                    path: "/nix/store/2vixb94v0hy2xc6p7mbnxxcyc095yyia-has-multi-out-lib"
+                        .to_string(),
+                    hash_with_mode: None,
+                },
+            );
+            b.insert(
+                "out".to_string(),
+                Output {
+                    path: "/nix/store/55lwldka5nyxa08wnvlizyqw02ihy8ic-has-multi-out".to_string(),
+                    hash_with_mode: None,
+                },
+            );
+            b
+        };
+        static ref EXP_AB_MAP: BTreeMap<String, BString> = {
+            let mut b = BTreeMap::new();
+            b.insert("a".to_string(), b"1".as_bstr().to_owned());
+            b.insert("b".to_string(), b"2".as_bstr().to_owned());
+            b
+        };
+    }
+
+    #[test_case(b"[(\"a\",\"1\"),(\"b\",\"2\")]", &EXP_AB_MAP, b""; "simple")]
+    fn parse_kv(input: &'static [u8], expected: &BTreeMap<String, BString>, exp_rest: &[u8]) {
+        let (rest, parsed) = super::parse_kv::<BString, _>(crate::aterm::parse_bstr_field)(input)
+            .expect("must parse");
+        assert_eq!(exp_rest, rest, "expected remainder");
+        assert_eq!(*expected, parsed);
+    }
+
+    #[test_case(
+        br#"("out","/nix/store/5vyvcwah9l9kf07d52rcgdk70g2f4y13-foo","","")"#,
+        ("out".to_string(), Output {
+            path: "/nix/store/5vyvcwah9l9kf07d52rcgdk70g2f4y13-foo".to_string(),
+            hash_with_mode: None
+        }); "simple"
+    )]
+    #[test_case(
+        br#"("out","/nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar","r:sha256","08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba")"#,
+        ("out".to_string(), Output {
+            path: "/nix/store/4q0pg5zpfmznxscq3avycvf9xdvx50n3-bar".to_string(),
+            hash_with_mode: Some(crate::derivation::NixHashWithMode::Recursive(
+                crate::nixhash::from_algo_and_digest (
+                   crate::nixhash::HashAlgo::Sha256,
+                   &data_encoding::HEXLOWER.decode(b"08813cbee9903c62be4c5027726a418a300da4500b2d369d3af9286f4815ceba").unwrap()
+                ).unwrap()
+            )),
+        }); "fod"
+     )]
+    fn parse_output(input: &[u8], expected: (String, Output)) {
+        let (rest, parsed) = super::parse_output(input).expect("must parse");
+        assert!(rest.is_empty());
+        assert_eq!(expected, parsed);
+    }
+
+    #[test_case(
+        br#"[("lib","/nix/store/2vixb94v0hy2xc6p7mbnxxcyc095yyia-has-multi-out-lib","",""),("out","/nix/store/55lwldka5nyxa08wnvlizyqw02ihy8ic-has-multi-out","","")]"#,
+        &EXP_MULTI_OUTPUTS;
+        "multi-out"
+    )]
+    fn parse_outputs(input: &[u8], expected: &BTreeMap<String, Output>) {
+        let (rest, parsed) = super::parse_outputs(input).expect("must parse");
+        assert!(rest.is_empty());
+        assert_eq!(*expected, parsed);
+    }
+}