swift-mirror/utils/swift_snapshot_tool

Swift Snapshot Tool

Used to list and bisect nightly snapshots off of swift.org.

Examples

List snapshots

# xcrun swift run swift_snapshot_tool list
[INFO] Starting to download snapshot information from github. 
[INFO] Finished downloading snapshot information from github. 
0 swift-DEVELOPMENT-SNAPSHOT-2024-09-06-a
1 swift-DEVELOPMENT-SNAPSHOT-2024-09-05-a
2 swift-DEVELOPMENT-SNAPSHOT-2024-09-04-a
3 swift-DEVELOPMENT-SNAPSHOT-2024-08-29-a
...

The number to the left is just the number back through historical time that the value is at. This allows for one to get a sense of the range of time in between two bisect numbers since one can look at the range in between them and how time varies.

Bisect

xcrun swift run swift_snapshot_tool bisect --script $SCRIPT_NAME --workspace $DIR_TO_DOWNLOAD_TOOLCHAINS \
   --good-tag $OLDER_TAG_NAME_THAT_PASSES --bad-tag $NEWER_TAG_NAME_THAT_FAILS

bisect success is defined by $SCRIPT_NAME returning 0 as an exit code. All other exit codes are considered a failure.

Options:

• workspace: This is the place where we will download toolchains to. Defaults to /tmp/swift_snapshot_tool_workspace_v1

• script: This is the script that should be run. We pass in the environment variables SWIFT_EXEC and SWIFT_FRONTEND to the subscript. If the script returns a zero exit code then the run is considered a succeess. If the script returns a non-zero exit code, then the run is considered a failure.

• good_tag: This is the older tag and is assumed to succeed by returning a zero exit code.

• bad_tag: This is the newer tag and is assumed to fail by returning a non-zero exit code.

• invert: This causes test.sh's result to be inverted. This allows one to bisect backwards from a good state to a bad state. This is useful to determine when an error was fixed.

• branch: This controls the specific branch of snapshots that are downloaded. By default uses development. Also supports the options 5.0 and 6.0.