Resolved Derivation

• 1. Property name
• 2. Property version
• 3. Property outputs
  • 3.1. Property Derivation Output
    • 3.1.1. Property Input-Addressed Output
      • 3.1.1.1. Property path
    • 3.1.2. Property Fixed Content-Addressed Output
      • 3.1.2.1. Property method
      • 3.1.2.2. Property hash
    • 3.1.3. Property Floating Content-Addressed Output
      • 3.1.3.1. Property method
      • 3.1.3.2. Property hashAlgo
    • 3.1.4. Property Deferred Output
    • 3.1.5. Property Impure Output
      • 3.1.5.1. Property impure
      • 3.1.5.2. Property method
      • 3.1.5.3. Property hashAlgo
• 4. Property system
• 5. Property builder
• 6. Property args
  • 6.1. args items
• 7. Property env
  • 7.1. Property additionalProperties
• 8. Property structuredAttrs
• 9. Property inputs
  • 9.1. Store Path

Title: Resolved Derivation

Description: Experimental JSON representation of a resolved Nix derivation (version 4).

This schema describes the JSON representation of Nix’s BasicDerivation type, which is a derivation with all input derivation dependencies resolved to store paths. This is the result of Derivation::tryResolve.

This is called “version 4” because we wish to keep it in sync with the primary (not necessarily resolved) JSON schema, but actually it is the first version for this format.

Warning

This JSON format is currently experimental and subject to change.

1. Property name

Title: Derivation name

Description: The name of the derivation. Used when calculating store paths for the derivation’s outputs.

2. Property version

Title: Format version (must be 4)

Description: Must be 4. This is a guard that allows us to continue evolving this format. The choice of 3 is fairly arbitrary, but corresponds to this informal version:

• Version 0: ATerm format

• Version 1: Original JSON format, with ugly "r:sha256" inherited from ATerm format.

• Version 2: Separate method and hashAlgo fields in output specs

• Version 3: Drop store dir from store paths, just include base name.

• Version 4: Two cleanups, batched together to lesson churn:

  • Reorganize inputs into nested structure (inputs.srcs and inputs.drvs)

  • Use canonical content address JSON format for floating content addressed derivation outputs.

Note that while this format is experimental, the maintenance of versions is best-effort, and not promised to identify every change.

Specific value: 4

3. Property outputs

Title: Output specifications

Description: Information about the output paths of the derivation. This is a JSON object with one member per output, where the key is the output name and the value is a JSON object as described.

Example

"outputs": {
  "out": {
    "method": "nar",
    "hashAlgo": "sha256",
    "hash": "6fc80dcc62179dbc12fc0b5881275898f93444833d21b89dfe5f7fbcbb1d0d62"
  }
}

3.1. Property Derivation Output

Title: Derivation Output

Description: A single output of a derivation, with different variants for different output types.

3.1.1. Property Input-Addressed Output

Title: Input-Addressed Output

Description: The traditional non-fixed-output derivation type. The output path is determined from the derivation itself.

See Input-addressing derivation outputs for more details.

3.1.1.1. Property path

Title: Output path

Description: The output path determined from the derivation itself.

3.1.2. Property Fixed Content-Addressed Output

Title: Fixed Content-Addressed Output

Description: The output is content-addressed, and the content-address is fixed in advance.

See Fixed-output content-addressing for more details.

3.1.2.1. Property method

Title: Content-Addressing Method

Description: Method of content addressing used for this output.

Must be one of:

• “flat”
• “nar”
• “text”
• “git”

3.1.2.2. Property hash

Title: Expected hash value

Description: The expected content hash.

Examples:

"sha256-ungWv48Bz+pBQUDeXa4iI7ADYaOWF3qctBD/YfIAFa0="

"sha512-IEqPxt2oLwoM7XvrjgikFlfBbvRosiioJ5vjMacDwzWW/RXBOxsH+aodO+pXeJygMa2Fx6cd1wNU7GMSOMo0RQ=="

3.1.3. Property Floating Content-Addressed Output

Title: Floating Content-Addressed Output

Description: Floating-output derivations, whose outputs are content addressed, but not fixed, and so the output paths are dynamically calculated from whatever the output ends up being.

See Floating Content-Addressing for more details.

3.1.3.1. Property method

Title: Content-Addressing Method

Description: Method of content addressing used for this output.

3.1.3.2. Property hashAlgo

Title: Hash algorithm

Description: What hash algorithm to use for the given method of content-addressing.

Must be one of:

• “blake3”
• “md5”
• “sha1”
• “sha256”
• “sha512”

3.1.4. Property Deferred Output

Title: Deferred Output

Description: Input-addressed output which depends on a (CA) derivation whose outputs (and thus their content-address are not yet known.

3.1.5. Property Impure Output

Title: Impure Output

Description: Impure output which is just like a floating content-addressed output, but this derivation runs without sandboxing. As such, we don’t record it in the build trace, under the assumption that if we need it again, we should rebuild it, as it might produce something different.

3.1.5.1. Property impure

Specific value: true

3.1.5.2. Property method

Title: Content-Addressing Method

Description: How the file system objects will be serialized for hashing.

3.1.5.3. Property hashAlgo

Title: Hash algorithm

Description: How the serialization will be hashed.

Must be one of:

• “blake3”
• “md5”
• “sha1”
• “sha256”
• “sha512”

4. Property system

Title: Build system type

Description: The system type on which this derivation is to be built (e.g. x86_64-linux).

5. Property builder

Title: Build program path

Description: Absolute path of the program used to perform the build. Typically this is the bash shell (e.g. /nix/store/p4xlj4imjbnm4v0x5jf4qysvyjjlgq1d-bash-4.4-p23/bin/bash).

6. Property args

Title: Builder arguments

Description: Command-line arguments passed to the builder.

6.1. args items

7. Property env

Title: Environment variables

Description: Environment variables passed to the builder.

7.1. Property additionalProperties

8. Property structuredAttrs

Title: Structured attributes

Description: Structured Attributes, only defined if the derivation contains them. Structured attributes are JSON, and thus embedded as-is.

9. Property inputs

Title: Input source paths

Description: List of store paths on which this resolved derivation depends. Since all derivation inputs have been resolved, only source paths remain.

Example

"inputs": [
  "b8nwz167km1yciqpwzjj24f8jcy8pq1h-separate-debug-info.sh",
  "f1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-dep1-out"
]

9.1. Store Path

Title: Store Path

Description: A store path identifying a store object.

This schema describes the JSON representation of store paths as used in various Nix JSON APIs.

Warning

This JSON format is currently experimental and subject to change.

Format

Store paths in JSON are represented as strings containing just the hash and name portion, without the store directory prefix.

For example: "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-foo.drv"

(If the store dir is /nix/store, then this corresponds to the path /nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-foo.drv.)

Structure

The format follows this pattern: ${digest}-${name}

• hash: Digest rendered in Nix32 (20 hash bytes become 32 ASCII characters)
• name: The package name and optional version/suffix information