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authorJoey Hess2015-12-05 17:52:43 -0400
committerJoey Hess2015-12-05 17:53:16 -0400
commit12548bae3d8feecce6a322162d91b827289ae824 (patch)
tree45f5ec5131817aab5133c9c1e4dbcf3364953e76 /src/Propellor/Types/ResultCheck.hs
parentb816e40e2618a8932144bceb7c7039adc5c44c11 (diff)
UncheckedProperty for cmdProperty et al
* Properties that run an arbitrary command, such as cmdProperty and scriptProperty are converted to use UncheckedProperty, since they cannot tell on their own if the command truely made a change or not. (API Change) Transition guide: - When GHC complains about an UncheckedProperty, add: `assume` MadeChange - Since these properties used to always return MadeChange, that change is always safe to make. - Or, if you know that the command should modifiy a file, use: `changesFile` filename * A few properties have had their Result improved, for example Apt.buldDep and Apt.autoRemove now check if a change was made or not.
Diffstat (limited to 'src/Propellor/Types/ResultCheck.hs')
-rw-r--r--src/Propellor/Types/ResultCheck.hs13
1 files changed, 13 insertions, 0 deletions
diff --git a/src/Propellor/Types/ResultCheck.hs b/src/Propellor/Types/ResultCheck.hs
index 6c2e1453..590d4ab9 100644
--- a/src/Propellor/Types/ResultCheck.hs
+++ b/src/Propellor/Types/ResultCheck.hs
@@ -5,6 +5,7 @@ module Propellor.Types.ResultCheck (
unchecked,
checkResult,
Checkable,
+ assume,
) where
import Propellor.Types
@@ -51,3 +52,15 @@ instance Checkable Property i where
instance Checkable UncheckedProperty i where
checkedProp (UncheckedProperty p) = p
+
+-- | Sometimes it's not practical to test if a property made a change.
+-- In such a case, it's often fine to say:
+--
+-- > someprop `assume` MadeChange
+--
+-- However, beware assuming `NoChange`, as that will make combinators
+-- like `onChange` not work.
+assume :: UncheckedProperty i -> Result -> Property i
+assume (UncheckedProperty p) result = adjustPropertySatisfy (checkedProp p) $ \satisfy -> do
+ r <- satisfy
+ return (r <> result)