Chan package:shake
How should you determine if a file has changed, used by
shakeChange. The most common values are
ChangeModtime
(the default, very fast,
touch causes files to rebuild) and
ChangeModtimeAndDigestInput (slightly slower,
touch
and switching
git branches does not cause input files to
rebuild).
Compare equality of file contents digests, a file has changed if its
digest changes. A touch will not force a rebuild. Use this
mode if modification times on your file system are unreliable.
Compare equality of modification timestamps, a file has changed if its
last modified time changes. A touch will force a rebuild.
This mode is fast and usually sufficiently accurate, so is the
default.
A file is rebuilt if both its modification time and digest have
changed. For efficiency reasons, the modification time is checked
first, and if that has changed, the digest is checked.
Use
ChangeModtimeAndDigest for input/source files and
ChangeModtime for output files. An input file is one which is a
dependency but is not built by Shake as it has no matching rule and
already exists on the file system.
A file is rebuilt if either its modification time or its digest has
changed. A touch will force a rebuild, but even if a files
modification time is reset afterwards, changes will also cause a
rebuild.
I recomputed the value and it was different.
I recomputed the value and it was the same.
The stored value has changed, but in a way that should be considered
identical (used rarely).
copyFileChanged old new copies the existing file from
old to new, if the contents have changed. The
old file will be tracked as a dependency. Also creates the
new directory if necessary.
Like
need but returns a list of rebuilt dependencies since the
calling rule last built successfully.
The following example writes a list of changed dependencies to a file
as its action.
"target" %> \out -> do
let sourceList = ["source1", "source2"]
rebuildList <- needHasChanged sourceList
writeFileLines out rebuildList
This function can be used to alter the action depending on which
dependency needed to be rebuild.
Note that a rule can be run even if no dependency has changed, for
example because of
shakeRebuild or because the target has
changed or been deleted. To detect the latter case you may wish to use
resultHasChanged.
Has a file changed. This function will only give the correct answer if
called in the rule producing the file,
before the rule has
modified the file in question. Best avoided, but sometimes necessary
in conjunction with
needHasChanged to cause rebuilds to happen
if the result is deleted or modified.
Write a file, but only if the contents would change.
How the output of a rule has changed.
At least one of my dependencies from last time have changed, or I have
no recorded dependencies.
How has the
RunResult changed from what happened last time.