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Diffstat (limited to 'src/Conftrack/Source.hs')
| -rw-r--r-- | src/Conftrack/Source.hs | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/src/Conftrack/Source.hs b/src/Conftrack/Source.hs index ecfa20d..ab13172 100644 --- a/src/Conftrack/Source.hs +++ b/src/Conftrack/Source.hs @@ -12,11 +12,27 @@ import Control.Monad.State (StateT (..)) import Data.Text (Text) +-- | An abstraction over "config sources". This might mean file formats, +-- environment variables, or any other kind of format that can be seen as a +-- key-value store. class ConfigSource s where + -- | Some sources require state, e.g. to keep track of which values were + -- already read. type SourceState s + + -- | read a single value from the source. fetchValue :: Key -> s -> StateT (SourceState s) IO (Either ConfigError (Value, Text)) + + -- | given @s@, determine if any keys are "left over" and were not used. + -- This is used to produce warnings for unknown configuration options; + -- since not all sources can support this, this function's return type + -- includes @Maybe@ and sources are free to return @Nothing@ if they + -- cannot determine if any unknown keys are present. leftovers :: s -> StateT (SourceState s) IO (Maybe [Key]) +-- | An opaque type for any kind of config sources. Values of this type can be +-- acquired from they @Conftrack.Source.*@ modules, or by implementing the +-- 'ConfigSource' type class. data SomeSource = forall source. ConfigSource source => SomeSource (source, SourceState source) |