Several fields in snapcraft.yaml are dependent on the architecture or the operating system being exposed to Snapcraft. This is accomplished using specific and advanced syntax within the YAML consumed by the snapcraft command.
This advanced grammar is made up of three nestable statements: on
, to
and try
:
The on statement
- on <selector>[,<selector>...]:
<grammar>|<primitive>
- else[ fail]:
<grammar>|<primitive>
<primitive>
may be either a list or a scalar, depending on the keyword.
The body of the on
clause is taken into account if every (AND, not OR) selector is true for the build environment. Currently the only selectors supported are host architectures (e.g. amd64
).
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 to statement
- [on <selector>[,<selector>...] ]to <selector>[,<selector>...]:
<grammar>|<primitive>
- else[ fail]:
<grammar>|<primitive>
<primitive>
may be either a list or a scalar, depending on the keyword.
The body of the to
clause is taken into account if every (AND, not OR) selector is true for the target environment. Currently the only selectors supported are target architectures (e.g. armhf
).
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 try statement
- try:
<grammar>|<primitive>
- else:
<grammar>|<primitive>
<primitive>
may be either a list or a scalar, depending on the keyword.
Warning:
The try statement does not work with builds using a base snap of core22
or later.
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.
Example
parts:
_part_name_:
stage-packages:
# libnuma1 package isn't available in armhf architecture, make it optional
- try:
- libnuma1