diff options
| -rw-r--r-- | pkgs/populate/src/flake.rs | 172 |
1 files changed, 140 insertions, 32 deletions
diff --git a/pkgs/populate/src/flake.rs b/pkgs/populate/src/flake.rs index ded7692..f992231 100644 --- a/pkgs/populate/src/flake.rs +++ b/pkgs/populate/src/flake.rs @@ -180,6 +180,78 @@ fn lock_has_input(locks: &Value, path: &[String]) -> bool { true } +/// The fields in output, each ending in a null byte, unless something +/// follows the last. +fn split_fields(output: &str) -> Option<Vec<String>> { + let mut fields: Vec<String> = output.split('\0').map(str::to_string).collect(); + // What follows the last null byte, empty if output ends with one. + fields.pop().filter(String::is_empty)?; + Some(fields) +} + +/// What derived_state sends back about a source's derived copy. +#[derive(Debug, PartialEq)] +struct DerivedState<'a> { + /// Where .populate/derived/<name>/original resolves to. + original: &'a str, + /// The key of the copy, or empty. + key: &'a str, + /// The store path the copy's result link points to, if the store has + /// it, or empty. + result: &'a str, + /// link or directory, if the target path is one, or empty. + target_kind: &'a str, + /// A line of sha256sum for each patch. + patch_sums: &'a [String], + /// The hash of each source drawn from, or empty if it's in the store. + hashes: &'a [String], +} + +impl<'a> DerivedState<'a> { + /// The state in the fields derived_state prints: four, those of the + /// patches up to an empty one, and then one for each of drawn sources. + fn parse(fields: &'a [String], drawn: usize) -> Option<DerivedState<'a>> { + let [original, key, result, target_kind, rest @ ..] = fields else { + return None; + }; + let separator = rest.iter().position(String::is_empty)?; + let (patch_sums, hashes) = (&rest[..separator], &rest[separator + 1..]); + if hashes.len() != drawn { + return None; + } + Some(DerivedState { + original, + key, + result, + target_kind, + patch_sums, + hashes, + }) + } +} + +/// The text whose hash is the key of a derived copy, like the shell +/// implementation computes it: the original's path, the spec, the patches' +/// sums, and, for a copy drawing inputs, nix flake lock's arguments and the +/// hashes of the sources drawn from that aren't in the store. +fn key_text( + original: &str, + spec: &Value, + patch_sums: &[String], + drawn_args: &[String], + hashes: &[String], +) -> String { + let mut text = format!("{original}\n{spec}\n"); + for line in patch_sums + .iter() + .chain(drawn_args) + .chain(hashes.iter().filter(|h| !h.is_empty())) + { + text += &format!("{line}\n"); + } + text +} + /// The store path a path below the store is in, and the rest of the path. fn split_store_path(path: &str) -> (&str, &str) { let end = path @@ -244,10 +316,9 @@ impl<'a> Flakes<'a> { let output = self .context .output(&Self::on_target(snippet, flakes), args)?; - let mut fields: Vec<String> = output.split('\0').map(str::to_string).collect(); - // What follows the last null byte. - fields.pop(); - Ok(fields) + split_fields(&output).ok_or_else(|| { + Failure::Message("error: the target sent back a field without its end".to_string()) + }) } /// Resolves paths on the target. @@ -497,19 +568,16 @@ impl<'a> Flakes<'a> { let mut state_args = vec![state.as_str(), target_path.as_str(), patch_dir.as_str()]; state_args.extend(drawn.iter().map(String::as_str)); let fields = self.fields(sh::draw::DERIVED_STATE, false, &state_args)?; - let malformed = - || Failure::Message(format!("error: can't read the state of source {name}")); - let [original, key_file, result, target_kind, rest @ ..] = fields.as_slice() else { - return Err(malformed()); - }; - let separator = rest - .iter() - .position(String::is_empty) - .ok_or_else(malformed)?; - let (patch_sums, hashes) = (&rest[..separator], &rest[separator + 1..]); - if hashes.len() != drawn.len() { - return Err(malformed()); - } + let DerivedState { + original, + key: old_key, + result, + target_kind, + patch_sums, + hashes, + } = DerivedState::parse(&fields, drawn.len()).ok_or_else(|| { + Failure::Message(format!("error: can't read the state of source {name}")) + })?; // Like Nix' toJSON: attributes sorted by name. let follows: Vec<Value> = self.follows[name] @@ -521,20 +589,9 @@ impl<'a> Flakes<'a> { "materialize": materialize, "rewriteLock": rewrite_lock, }); - let mut text = format!("{original}\n{spec}\n"); - for sum in patch_sums { - text += &format!("{sum}\n"); - } - if !drawn.is_empty() { - for arg in &args { - text += &format!("{arg}\n"); - } - for hash in hashes.iter().filter(|h| !h.is_empty()) { - text += &format!("{hash}\n"); - } - } - let key = sha256_hex(text.as_bytes()); - let unchanged = *key_file == key; + let drawn_args: &[String] = if drawn.is_empty() { &[] } else { &args }; + let key = sha256_hex(key_text(original, &spec, patch_sums, drawn_args, hashes).as_bytes()); + let unchanged = old_key == key; if materialize { if !unchanged || target_kind != "directory" { @@ -565,7 +622,7 @@ impl<'a> Flakes<'a> { } let (path, subdir) = split_store_path(original); - let result = if unchanged { result.as_str() } else { "" }; + let result = if unchanged { result } else { "" }; let mut all = vec![ state.as_str(), path, @@ -842,6 +899,57 @@ mod tests { ); } + fn strings(fields: &[&str]) -> Vec<String> { + fields.iter().map(|f| f.to_string()).collect() + } + + #[test] + fn fields() { + assert_eq!(split_fields(""), Some(vec![])); + assert_eq!(split_fields("a\0\0b\0"), Some(strings(&["a", "", "b"]))); + assert_eq!(split_fields("a\0b"), None); + } + + #[test] + fn derived_states() { + let fields = strings(&["/nix/store/o", "k", "", "link", "s1", "s2", "", "h", ""]); + assert_eq!( + DerivedState::parse(&fields, 2), + Some(DerivedState { + original: "/nix/store/o", + key: "k", + result: "", + target_kind: "link", + patch_sums: &strings(&["s1", "s2"]), + hashes: &strings(&["h", ""]), + }) + ); + // A field missing, or one too many. + assert_eq!(DerivedState::parse(&fields, 3), None); + assert_eq!(DerivedState::parse(&fields, 1), None); + assert_eq!(DerivedState::parse(&fields[..3], 0), None); + // No end of the patches. + assert_eq!( + DerivedState::parse(&strings(&["o", "k", "r", "t", "s"]), 0), + None + ); + } + + #[test] + fn key_texts() { + let spec = json!({ "follows": [], "materialize": false, "rewriteLock": false }); + assert_eq!( + key_text( + "/nix/store/o", + &spec, + &strings(&["s /p/0001-x.patch"]), + &strings(&["--override-input", "a", "path:/b"]), + &strings(&["h", ""]), + ), + "/nix/store/o\n{\"follows\":[],\"materialize\":false,\"rewriteLock\":false}\ns /p/0001-x.patch\n--override-input\na\npath:/b\nh\n" + ); + } + #[test] fn url_paths() { assert_eq!(url_path("/var/src/a-b_c.d~e"), "/var/src/a-b_c.d~e"); |