thrift-haskell
Haskell thrift codegen and runtime library, working in progress.
thrift-haskell-compiler
Following're some rules for IDL compiler:
- Haskell module name will be camelized and capitalized path/filename relative to
CWD
, for example:
...
├── IDL
│ ├── rockstable.thrift
│ └── rockstable_master.thrift
...
If you run thrift-haskell-compiler -o data ./IDL
, you will get your compiled files in:
├── Data
│ └── Idl
│ ├── Rockstable.hs
│ └── RockstableMaster.hs
├── IDL
│ ├── rockstable.thrift
│ └── rockstable_master.thrift
-
Identifier will be camelized (and capitalized if needed).
-
Type definitions will be compiled into
type
declarations.
typedef list<Tweet> TweetList
will be compiled to:
type TweetList = [Tweet]
-
Senum and Slist are deprecated, thus unsupportted.
-
Enum is very straightforward, except that hex numeric literals are not supportted(which follows the thrift spec AFAICT).
enum TweetType {
TWEET,
RETWEET = 2,
DM = 0xa, // this field's behavior is undefined
REPLY
}
will compiled to:
data TweetType = Tweet
| Retweet
| Dm
| Reply
deriving (Eq, Ord, Show, Thrift.Data, Thrift.Typeable,
Thrift.Generic, Thrift.Hashable)
instance Enum TweetType where
fromEnum Tweet = 0
fromEnum Retweet = 2
fromEnum Dm = 4
fromEnum Reply = 5
toEnum 0 = Tweet
toEnum 2 = Retweet
toEnum 4 = Dm
toEnum 5 = Reply
instance Thrift.Thrift TweetType where
typeCode = Thrift.TypeCode Thrift.tcInt32
defaultValue = Tweet
toTValue Tweet = Thrift.TInt32 0
toTValue Retweet = Thrift.TInt32 2
toTValue Dm = Thrift.TInt32 4
toTValue Reply = Thrift.TInt32 5
fromTValue (Thrift.TInt32 0) = Tweet
fromTValue (Thrift.TInt32 2) = Retweet
fromTValue (Thrift.TInt32 4) = Dm
fromTValue (Thrift.TInt32 5) = Reply
fromTValue _ = error "bad enum value"
- Struct field will be prepend with struct name to eliminate name collision, Every field must have a unique, positive integer identifier:
struct Tweet {
1: required i32 userId;
2: required string userName;
3: required string text;
4: optional Location loc;
5: optional TweetType tweetType = TweetType.TWEET;
16: optional string language = "english";
}
will compiled to:
data Tweet = Tweet{tweetUserId :: Thrift.Int32,
tweetUserName :: Thrift.Text, tweetText :: Thrift.Text,
tweetLoc :: Maybe Location, tweetTweetType :: Maybe TweetType,
tweetLanguage :: Maybe Thrift.Text}
deriving (Eq, Show, Thrift.Data, Thrift.Typeable, Thrift.Generic,
Thrift.Hashable)
instance Thrift.Thrift Tweet where
typeCode = Thrift.TypeCode Thrift.tcStruct
defaultValue
= let tweetUserId = Thrift.defaultValue
tweetUserName = Thrift.defaultValue
tweetText = Thrift.defaultValue
tweetLoc = Nothing
tweetTweetType = Just Tweet
tweetLanguage = Just "english"
in Tweet{..}
toTValue Tweet{..}
= Thrift.TStruct
(Thrift.catMaybes
[Just (1, Thrift.toTValue tweetUserId),
Just (2, Thrift.toTValue tweetUserName),
Just (3, Thrift.toTValue tweetText),
case tweetLoc of
Just x -> Just (4, Thrift.toTValue x)
_ -> Nothing,
case tweetTweetType of
Just x -> Just (5, Thrift.toTValue x)
_ -> Nothing,
case tweetLanguage of
Just x -> Just (16, Thrift.toTValue x)
_ -> Nothing])
fromTValue (Thrift.TStruct x)
= let m = Thrift.fromList x
tweetUserId = Thrift.lookupRequired (fromIntegral 1) m
tweetUserName = Thrift.lookupRequired (fromIntegral 2) m
tweetText = Thrift.lookupRequired (fromIntegral 3) m
tweetLoc = Thrift.lookupOptional Nothing (fromIntegral 4) m
tweetTweetType
= Thrift.lookupOptional (Just Tweet) (fromIntegral 5) m
tweetLanguage
= Thrift.lookupOptional (Just "english") (fromIntegral 16) m
in Tweet{..}
fromTValue _ = error "bad struct value"
Please notice that there exists a so called default field type, it's treated like required
field in data declarations, eg. without Maybe
. Because haskell really don't have a undefined/nil
notation, every field must be present as long as it is not optional. During deserialization, if peer doesn't send a default field, a defaultValue
will be used, for basic types those are:
bool: false
i8, i16, i32, i64, double : 0
string: ""
binary: ""
MapType: []
SetType: []
ListType: []
This may seemed arbitrary, but you will set these default field anyway so the choice of defaults are not important here, and you can supply a default value using thift's syntax. Following is a table describe every possible scenario:
field requireness | data type | serialize | deserialize | deserialize when user supply a default value x |
---|---|---|---|---|
required | a | always | must present, otherwise error | ignore user supply value x |
optional | Maybe a | if Just | not present == Nothing | not present == Just x |
default(function return) | a | always | not present == Thrift.def | not present == x |
The term present here means a field can be find by its identifier AND the type conversion is successful, if a field with same identifier but different type exists, we will simply call error. Note we won't do any implicit conversion, that means a Int32
field x is NOT present even there is an IntX
field x.
License
Copyright (c) 2016, Winterland
All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following
disclaimer in the documentation and/or other materials provided
with the distribution.
* Neither the name of winterland1989 nor the names of other
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.