Struct Derivation

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pub struct Derivation {
    pub arguments: Vec<String>,
    pub builder: String,
    pub environment: BTreeMap<String, BString>,
    pub input_derivations: BTreeMap<StorePath<String>, BTreeSet<String>>,
    pub input_sources: BTreeSet<StorePath<String>>,
    pub outputs: BTreeMap<String, Output>,
    pub system: String,
}

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§arguments: Vec<String>§builder: String§environment: BTreeMap<String, BString>§input_derivations: BTreeMap<StorePath<String>, BTreeSet<String>>

Map from drv path to output names used from this derivation.

§input_sources: BTreeSet<StorePath<String>>

Plain store paths of additional inputs.

§outputs: BTreeMap<String, Output>

Maps output names to Output.

§system: String

Implementations§

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impl Derivation

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pub fn validate( &self, validate_output_paths: bool, ) -> Result<(), DerivationError>

validate ensures a Derivation struct is properly populated, and returns a DerivationError if not.

if validate_output_paths is set to false, the output paths are excluded from validation.

This is helpful to validate struct population before invoking Derivation::calculate_output_paths.

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impl Derivation

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pub fn serialize(&self, writer: &mut impl Write) -> Result<(), Error>

write the Derivation to the given std::io::Write, in ATerm format.

The only errors returns are these when writing to the passed writer.

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fn serialize_with_replacements( &self, writer: &mut impl Write, input_derivations: &BTreeMap<impl AtermWriteable, BTreeSet<String>>, ) -> Result<(), Error>

Like serialize but allow replacing the input_derivations for hash calculations.

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pub fn to_aterm_bytes(&self) -> Vec<u8> ⓘ

return the ATerm serialization.

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fn to_aterm_bytes_with_replacements( &self, input_derivations: &BTreeMap<impl AtermWriteable, BTreeSet<String>>, ) -> Vec<u8> ⓘ

Like to_aterm_bytes, but accept a different BTreeMap for input_derivations. This is used to render the ATerm representation of a Derivation “modulo fixed-output derivations”.

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pub fn from_aterm_bytes(b: &[u8]) -> Result<Derivation, Error<&[u8]>>

Parse an Derivation in ATerm serialization, and validate it passes our set of validations.

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pub fn calculate_derivation_path( &self, name: &str, ) -> Result<StorePath<String>, DerivationError>

Returns the drv path of a Derivation struct.

The drv path is calculated by invoking build_text_path, using the name with a .drv suffix as name, all Derivation::input_sources and keys of Derivation::input_derivations as references, and the ATerm string of the Derivation as content.

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pub fn fod_digest(&self) -> Option<[u8; 32]>

Returns the FOD digest, if the derivation is fixed-output, or None if it’s not. TODO: this is kinda the string from build_ca_path with a CAHash::Flat, what’s fed to build_store_path_from_fingerprint_parts (except the out_output.path being an empty string)

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pub fn hash_derivation_modulo<F>( &self, fn_lookup_hash_derivation_modulo: F, ) -> [u8; 32]
where F: Fn(&StorePathRef<'_>) -> [u8; 32],

Calculates the hash of a derivation modulo fixed-output subderivations.

This is called hashDerivationModulo in nixcpp.

It returns the sha256 digest of the derivation ATerm representation, except that:

any input derivation paths have beed replaced “by the result of a recursive call to this function” and that
for fixed-output derivations the special fixed:out:${algo}:${digest}:${fodPath} string is hashed instead of the A-Term.

It’s up to the caller of this function to provide a (infallible) lookup function to query [hash_derivation_modulo] of direct input derivations, by their StorePathRef. It will only be called in case the derivation is not a fixed-output derivation.

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pub fn calculate_output_paths( &mut self, name: &str, hash_derivation_modulo: &[u8; 32], ) -> Result<(), DerivationError>

This calculates all output paths of a Derivation and updates the struct. It requires the struct to be initially without output paths. This means, self.outputs[$outputName].path needs to be an empty string, and self.environment[$outputName] needs to be an empty string.

Output path calculation requires knowledge of the [hash_derivation_modulo], which (in case of non-fixed-output derivations) also requires knowledge of the [hash_derivation_modulo] of input derivations (recursively).

To avoid recursing and doing unnecessary calculation, we simply ask the caller of this function to provide the result of the [hash_derivation_modulo] call of the current Derivation, and leave it up to them to calculate it when needed.

On completion, self.environment[$outputName] and self.outputs[$outputName].path are set to the calculated output path for all outputs.