Snapcraft filesets

A fileset is used within snapcraft.yaml to represent a group of files, or a single file, when creating a snap.

They’re useful when moving files into the stage and prime areas of the build process (see Snapcraft lifecycle for more details) as they can be referenced individually, rather than always having to construct a list of filenames.

A fileset is implemented as a YAML map between the fileset name (the key) and a list of corresponding filenames for each fileset. This list can be built from any of the following:

• individual files, eg. [ bin/dnsmasq ]
• subdirectory paths, eg. [ etc ]
• wildcard globs, eg. [ usr/* ]
• globstar globs, eg. [ lib/**/*.so* ]

The * (asterisk) wildcard glob returns all the files in that path. Conversely, adding an initial - (dash) will exclude the files in that path. For example, you could add usr/local/* then remove usr/local/man/* with the following:

filesets:
   allbutman: [ usr/local/*, -usr/local/man/* ]

Filenames are relative to the part install directory, eg. parts/<part-name>/install.

If you have used the organize keyword to rename files from your snapcraft.yaml part, your fileset will be built from filenames after they’re renamed.

Conflicting rules example

Snapcraft will attempt to aggregate conflicting rules from different filesets. For example, take the following directory and file structure:

adir
├── adirthat
├── adirthis
└── bdir
    ├── bdirthat
    └── bdirthis

The following fileset definition will not stage adir/bdir/* despite its specific inclusion under adir/*:

filesets:
  exclude-dir: [ -adir/bdir/* ]
  include-dir: [ adir/* ]
stage:
  - $include-dir
  - $exclude-dir

In the above example, using the excluding syntax adir/bdir instead of adir/bdir/* would exclude both the bdir directory and its contents, rather than excluding only the contents, retaining the empty bdir itself.

This is how the above will be staged within the snap:

adir
├── adirthat
├── adirthis
└── bdir

If, however, we remove the exclude-dir: [ -adir/bdir/* ] fileset definition, all the files and directories beneath adir will be staged in the snap:

adir
├── adirthat
├── adirthis
└── bdir
    ├── bdirthat
    └── bdirthis

Relevant Snapcraft source code

Check out the _organize_filesets function in snapcraft_legacy/internal/pluginhandler/init.py

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Last updated 9 months ago.