ghc-exactprint
ghc-exactprint copied to clipboard
alanz
Usage examples?
I'm having a go at using exactprint to add an explicit export list for a module. So starting from something without an explicit export list, I should get
module Test.ExportExplicit (isExported, anotherExport, andAnother) where
isExported = (+1)
anotherExport = True
andAnother = 27
main :: IO ()
main = pure ()
So far, I get almost the right output; it is missing commas:
module Test.ExportImplicit (alsoExportedisExportedmain) where
isExported = (+1)
alsoExported = True
main :: IO ()
main = print $ isExported 1
The core of my code is
22 mkIEVarFromNameT :: Monad m => Name -> TransformT m (Located (IE GhcPs))
23 mkIEVarFromNameT name = do
24 loc <- uniqueSrcSpanT
25 return $ L
26 loc
27 (IEVar noExt
28 (L loc (IEName (L loc (mkVarUnqual ((occNameFS . occName) name)))))
29 )
30
31 addExportDeclAnnT :: Monad m => Located (IE GhcPs) -> TransformT m ()
32 addExportDeclAnnT (L _ (IEVar _ (L _ (IEName x)))) =
33 addSimpleAnnT x (DP (0, 0)) [(G AnnVal, DP (0, 0))]
34
35 mkNamesFromAvailInfos :: [AvailInfo] -> [Name]
36 mkNamesFromAvailInfos = concatMap availNames -- there are also other choices
94 addExports
95 :: DynFlags
96 -> [AvailInfo]
97 -> (Anns, Located (HsModule GhcPs))
98 -> (Anns, Located (HsModule GhcPs))
99 addExports dflags exports (anns, ast@(L astLoc hsMod)) = do
100 let
101 names = mkNamesFromAvailInfos exports
102 (exports', (anns', n), s) =
103 --
104 runTransform anns $ mapM mkIEVarFromNameT names
105
106 addExportDecls
107 :: [Located (IE GhcPs)] -> Transform (Located (HsModule GhcPs))
108 addExportDecls expl = do
109 let hsMod' = hsMod { hsmodExports = Just $ L astLoc expl }
110 mapM_ addTrailingCommaT expl -- init expl
111 mapM_ addExportDeclAnnT expl
112 addSimpleAnnT (L astLoc expl)
113 (DP (0, 1))
114 [(G AnnOpenP, DP (0, 0)), (G AnnCloseP, DP (0, 0))]
115 return (L astLoc hsMod')
116
117 (ast', (anns'', n'), s') = runTransform anns' (addExportDecls exports')
118
119 (anns'', ast')
anns'' contains no comma annotations, whereas I would have expected the result to be something like the following (generated by brittany)
A Just (Ann (DP (0,0)) [] [] [((G AnnModule),DP (0,0)),((G AnnVal),DP (0,1)),((G AnnWhere),DP (0,1)),((G AnnEofPos),DP (1,0))] Nothing Nothing)
HsModule
Just (A (Nothing) {abstract:ModuleName})
Just
A Just (Ann (DP (0,1)) [] [] [((G AnnOpenP),DP (0,0)),((G AnnCloseP),DP (0,0))] Nothing Nothing)
[ A Just (Ann (DP (0,0)) [] [] [((G AnnComma),DP (0,0))] Nothing Nothing)
IEVar
NoExt
A Just (Ann (DP (0,0)) [] [] [] Nothing Nothing)
IEName
A Just (Ann (DP (0,0)) [] [] [((G AnnVal),DP (0,0))] Nothing Nothing)
Unqual {OccName: isExported}
, A Just (Ann (DP (0,1)) [] [] [((G AnnComma),DP (0,0))] Nothing Nothing)
IEVar
NoExt
A Just (Ann (DP (0,0)) [] [] [] Nothing Nothing)
IEName
A Just (Ann (DP (0,0)) [] [] [((G AnnVal),DP (0,0))] Nothing Nothing)
Unqual {OccName: anotherExport}
, A Just (Ann (DP (0,1)) [] [] [] Nothing Nothing)
IEVar
NoExt
A Just (Ann (DP (0,0)) [] [] [] Nothing Nothing)
IEName
A Just (Ann (DP (0,0)) [] [] [((G AnnVal),DP (0,0))] Nothing Nothing)
Unqual {OccName: andAnother}
]
I'm clearly not applying addTrailingCommaT correctly at line 110. Is there an obvious bug, or is there a better example of how to generate the additional syntax from a given list of '[Name]'? The only libraries that seem to use ghc-exacprint are apply-refact, brittany, HaRe, hgrep, lens-th-rewrite, retrie and smuggler, but I haven't found anything that is obviously on point in them. Thanks.
PS: ppr ast' seems to put in its own brackets
module Test.ExportImplicit (
alsoExported, isExported, main
) where
isExported = (+ 1)
alsoExported = True
main :: IO ()
main = print $ isExported 1
In lines 24-29 (mkIEVarFromNameT) you reuse the same unique loc, which means that there is one AnnKey shared between IEVar, IEName and Unqual. As a consequence, in line 111 you overwrite the annotation value that was modified in 110.
Or written in imperative style, your code roughly reads as
024 loc1 = loc2 = loc3 = generateUnique();
110 myAnnMap[loc1].annsDP = myMap[loc1].annsDP ++ [comma];
111 myAnnMap[loc2] = { dp = .., annsDP = .. };
Thanks for looking, Lennart. I'm clearly being thick, but the following produces the same result.
mkIEVarFromNameT :: Monad m => Name -> TransformT m (Located (IE GhcPs))
23 mkIEVarFromNameT name = do
24 locIEVar <- uniqueSrcSpanT
25 locIEName <- uniqueSrcSpanT
26 locUnqual <- uniqueSrcSpanT
27 return $ L
28 locIEVar
29 (IEVar
30 noExt
31 (L locIEName
32 (IEName (L locUnqual (mkVarUnqual ((occNameFS . occName) name))))
33 )
34 )
Oh, right. Try refactoring the code so that you only do one runTransform. The return value from uniqueSrcSpanT is only as unique as the state of the Transform, and every runTransform sets it to the same 0. So you still share keys atm.
Although you only have 2 runTransforms, I thought you had more. Maybe try testing this hypothesis by using runTransformFrom n in line 117.
If that works you can refactor the code to clean it up. It should be a bit cleaner with a single runTransform on the outside.
hm no, you don't use uniqueSrcSpanT in the second runTransform. But I don't trust yet that you don't have overlapping keys nonetheless. Maybe the whole addExports should be a monadic Transform (HsModule GhcPs).
Thanks to your first hins, I got the following to work! This is probably more by luck than by analysis, so it's probably buggy, and I need to simplify it. I'll have a go with the runTransformFrom n.
In your refactoring suggestion, do you mean composing the various annotation steps into one? I think that adding the () and annotating the IEVar still need to be two steps. But I could take the runTransform out of addExportDecls to the call site?
22 mkNamesFromAvailInfos :: [AvailInfo] -> [Name]
23 mkNamesFromAvailInfos = concatMap availNames -- there are also other choices
24
25 mkIEVarFromNameT :: Monad m => Name -> TransformT m (Located (IE GhcPs))
26 mkIEVarFromNameT name = do
27 loc <- uniqueSrcSpanT
28 return $ L
29 loc
30 (IEVar noExt
31 (L loc (IEName (L loc (mkVarUnqual ((occNameFS . occName) name)))))
32 )
33
34 addExportDeclAnnT :: Monad m => Located (IE GhcPs) -> TransformT m ()
35 addExportDeclAnnT (L _ (IEVar _ (L _ (IEName x)))) =
36 addSimpleAnnT x (DP (1, 2)) [(G AnnVal, DP (0, 0))]
37
38 addCommaT :: Monad m => Located (IE GhcPs) -> TransformT m ()
39 addCommaT x@(L _ (IEVar _ (L _ (IEName _)))) =
40 addSimpleAnnT x (DP (0, 0)) [(G AnnComma, DP (0, 0))]
93 addExports
94 :: DynFlags
95 -> [AvailInfo]
96 -> (Anns, Located (HsModule GhcPs))
97 -> (Anns, Located (HsModule GhcPs))
98 addExports dflags exports (anns, ast@(L astLoc hsMod)) = do
99 let
100 names = mkNamesFromAvailInfos exports
101 (exports', (anns', n), s) =
102 -- runTransform :: Anns -> Transform a -> (a, (Anns, Int), [String])
103 runTransform anns $ mapM mkIEVarFromNameT names
104
105 addExportDecls
106 :: [Located (IE GhcPs)] -> Transform (Located (HsModule GhcPs))
107 addExportDecls expl = do
108 let hsMod' = hsMod { hsmodExports = Just $ L astLoc expl }
109 addSimpleAnnT (L astLoc expl)
110 (DP (0, 1))
111 [(G AnnOpenP, DP (0, 0)), (G AnnCloseP, DP (0, 1))]
112 mapM_ addExportDeclAnnT expl
113 mapM_ addCommaT (init expl)
114 return (L astLoc hsMod')
115
116 (ast', (anns'', n'), s') = runTransform anns' (addExportDecls exports')
117
118 (anns'', ast')
I recommend to Debug.Trace.trace the involved keys/locs to diagnose this. astLoc in line 98 and loc in 27 might still be the same.
Using traceM I got
astLoc: RealSrcSpan SrcSpanPoint "test/Test/ExportImplicit.hs" 1 1
loc: RealSrcSpan SrcSpanPoint "ghc-exactprint" -1 0
loc: RealSrcSpan SrcSpanPoint "ghc-exactprint" -1 1
loc: RealSrcSpan SrcSpanPoint "ghc-exactprint" -1 2
If you have suggestions for cleaning up the code, they'd be v welcome.
oh, that is good to know. So I was wrong about the "overlapping keys" idea.
The difference is just addTrailingCommaT vs addSimpleAnnT - the former does not add an annotation to the map if it does not exist. I missed that detail earlier. The correct translation would have been:
024 loc1 = loc2 = loc3 = generateUnique(); 110 if (myAnnMap[loc1]) { myAnnMap[loc1].annsDP = myMap[loc1].annsDP ++ [comma] }; 111 myAnnMap[outerLoc] = { dp = .., annsDP = .. };
Sorry for pushing in the wrong directions with my attempts of debugging this. Glad you got something working. I am still confused why it works to be honest, because you are sharing keys again, and it seems you overwrite the annotations containing AnnVal. But maybe I overlook something.
I'd refactor it like this (doing this blind, hopefully it is not too broken):
addExports
:: DynFlags
-> [AvailInfo]
-> (Anns, Located (HsModule GhcPs))
-> (Anns, Located (HsModule GhcPs))
addExports dflags exports (anns, ast@(L astLoc hsMod)) =
-- runTransform :: Anns -> Transform a -> (a, (Anns, Int), [String])
let (ast', (anns', _), s') = runTransform anns $ do
let names = mkNamesFromAvailInfos exports
(exports', (anns', n), s) <- mapM mkIEVarFromNameT names
let addExportDecls
:: [Located (IE GhcPs)] -> Transform (Located (HsModule GhcPs))
addExportDecls expl = do
let hsMod' = hsMod { hsmodExports = Just $ L astLoc expl }
addSimpleAnnT
(L astLoc expl)
(DP (0, 1))
[(G AnnOpenP, DP (0, 0)), (G AnnCloseP, DP (0, 1))]
mapM_ addExportDeclAnnT expl
mapM_ addCommaT (init expl)
return (L astLoc hsMod')
addExportDecls exports'
in (anns', ast')
Many thanks. That was v helpful and allowed me to clean up further to:
58 addExplicitExports
59 :: DynFlags
60 -> [AvailInfo]
61 -> (Anns, Located (HsModule GhcPs))
62 -> (Anns, Located (HsModule GhcPs))
63 addExplicitExports dflags exports (anns, L astLoc hsMod) = (anns', ast')
64 where
65 (ast', (anns', _n), _s) = runTransform anns $ do
66
67 let names = mkNamesFromAvailInfos exports
68 exportsList <- mapM mkIEVarFromNameT names
69
70 let lExportsList = L astLoc exportsList
71 hsMod' = hsMod { hsmodExports = Just lExportsList }
72 addParensT lExportsList
73 mapM_ addExportDeclAnnT exportsList
74 unless (null exportsList) $ mapM_ addCommaT (init exportsList)
75 return (L astLoc hsMod')
with
14 mkNamesFromAvailInfos :: [AvailInfo] -> [Name]
15 mkNamesFromAvailInfos = concatMap availNames -- there are also other choices
16
17 mkIEVarFromNameT :: Monad m => Name -> TransformT m (Located (IE GhcPs))
18 mkIEVarFromNameT name = do
19 locIEVar <- uniqueSrcSpanT
20 locIEName <- uniqueSrcSpanT
21 locUnqual <- uniqueSrcSpanT
22 return $
23 L
24 locIEVar
25 ( IEVar
26 noExt
27 ( L
28 locIEName
29 (IEName (L locUnqual (mkVarUnqual ((occNameFS . occName) name))))
30 )
31 )
32
33 addExportDeclAnnT :: Monad m => Located (IE GhcPs) -> TransformT m ()
34 addExportDeclAnnT (L _ (IEVar _ (L _ (IEName x)))) =
35 addSimpleAnnT x (DP (1, 2)) [(G AnnVal, DP (0, 0))]
36
37 addCommaT :: Monad m => Located (IE GhcPs) -> TransformT m ()
38 addCommaT x = addSimpleAnnT x (DP (0, 0)) [(G AnnComma, DP (0, 0))]
39
40 addParensT :: Monad m => Located [Located (IE GhcPs)] -> TransformT m ()
41 addParensT x =
42 addSimpleAnnT
43 x
44 (DP (0, 1))
45 [(G AnnOpenP, DP (0, 0)), (G AnnCloseP, DP (0, 1))]
which seems much more satisfying.
I'll restored the 3 different invocations just in case ...
I'm happy to provide further debugging output if it'd help unravel the conundrum, or take any further stylistic improvements.
Many thanks for your time.
That looks good.
I just noticed that the AnnKeys are different if they are on different constructors. So because you have a IEVar, a IEName and an Unqual you should be safe sharing the SrcSpan. Maybe it is a good idea in general to avoid that because you might forget about it and share it on the same constructor in the future, but technically it is not necessary here. This is the reason why the other version worked.
Thanks. Noted.
To come back to the original original question, it'd be great to have some fuller top-level documentation or examples of the use of this library and where the pitfalls are.