Several fields in snapcraft.yaml are dependent on the architecture or the operating system being exposed to Snapcraft. This is accomplished using a specific and advanced syntax within the YAML consumed by the snapcraft command.
The following build-packages section, for example, evaluates and then defines which build packages to install depending on the target environment (to) for the snap:
build-packages:
- to arm64:
- g++-multilib-arm-linux-gnueabihf
- gcc-multilib-arm-linux-gnueabihf
- else:
- gcc-multilib
- g++-multilib
This advanced grammar is made up of three nestable statements: to, on and try.
The to statement
- to <selector>:
<grammar>|<primitive>
- else:
<grammar>|<primitive>
The body of the to clause is taken into account if every (AND, not OR) selector is true for the target environment.
The only selectors currently supported are host and target architectures (e.g. amd64 ).
<primitive> may be either a list or a scalar, depending on whether the keyword is a command-delimited list of names or not.
If the to clause doesn’t match and is immediately followed by an else clause, the else clause must be satisfied. A to clause without an else clause is considered satisfied even if no selector matched. The else fail form allows for the generation of an error if a to clause is not matched.
Optionally an ‘on’ statement can precede a 'to' in the same line to form a compound statement. Used this way, the selectors of both statements have to be true. That is to say, both the build environment and the target have to be true for the body of the clause to be taken into account.
The on statement
- on <selector>[,<selector>...]:
<grammar>|<primitive>
- else[fail]:
<grammar>|<primitive>
The body of the on clause is taken into account if every (AND, not OR) selector is true for the build environment.
The only selectors currently supported are host and target architectures (e.g. amd64).
<primitive> may be either a list or a scalar, depending on whether the keyword is a command-delimited list of names or not.
If the on clause doesn’t match and is immediately followed by an else clause, the else clause must be satisfied. An on clause without an else clause is considered satisfied even if no selector matched. The else fail form allows for the generation of an error if a to clause is not matched.
The try statement
- try:
<grammar>|<primitive>
- else:
<grammar>|<primitive>
The body of the try clause is taken into account only when all primitives contained within it are valid (primitive validity is determined on a keyword-specific basis). If they are not all valid, and are immediately followed by else clauses, those are tried in order, and one of them must be satisfied. A try clause with no ‘else’ clause is considered satisfied even if it contains invalid primitives.
<primitive> may be either a list or a scalar, depending on whether the keyword is a command-delimited list of names or not.
Warning:
The try statement does not work with builds using a base snap of core22 or later.
Example
The following two examples will set different environment variables for the build stage, depending on the host (on) and target (to) architectures:
build-environment:
- on amd64 to arm64:
- FOO: BAR
- on amd64 to armhf:
- FOO: BAZ
build-environment:
- on amd64 to [arm64,armhf]:
- FOO: BAR
- on amd64 to riscv64:
- FOO: BAZ
Last updated 9 months ago.