`cabal install` failure with GHC 8.10

[sjakobi]

For some reason, cabal install vgrep tried to build v0.1.4.1 for me, which unfortunately fails:

src/Vgrep/Environment/Config.hs:28:25: error:
    Not in scope: type constructor or class ‘Attr’
   |
28 |     { _lineNumbers   :: Attr
   |                         ^^^^

src/Vgrep/Environment/Config.hs:31:25: error:
    Not in scope: type constructor or class ‘Attr’
   |
31 |     , _lineNumbersHl :: Attr
   |                         ^^^^

src/Vgrep/Environment/Config.hs:34:25: error:
    Not in scope: type constructor or class ‘Attr’
   |
34 |     , _normal        :: Attr
   |                         ^^^^

src/Vgrep/Environment/Config.hs:37:25: error:
    Not in scope: type constructor or class ‘Attr’
   |
37 |     , _normalHl      :: Attr
   |                         ^^^^

src/Vgrep/Environment/Config.hs:40:25: error:
    Not in scope: type constructor or class ‘Attr’
   |
40 |     , _fileHeaders   :: Attr
   |                         ^^^^

src/Vgrep/Environment/Config.hs:44:25: error:
    Not in scope: type constructor or class ‘Attr’
   |
44 |     , _selected      :: Attr
   |                         ^^^^

Here's the output when I try to force cabal to install the latest v0.2.2.0:

$ cabal install vgrep --constraint 'vgrep ==0.2.2.0' --minimize-conflict-set
Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] trying: vgrep-0.2.2.0 (user goal)
[__1] trying: template-haskell-2.16.0.0/installed-2.16.0.0 (dependency of
vgrep)
[__2] next goal: aeson (dependency of vgrep)
[__2] rejecting: aeson-1.5.4.0 (conflict: vgrep => aeson>=0.11 && <1.3 ||
>=0.9 && <0.10)
[__2] skipping: aeson-1.5.3.0, aeson-1.5.2.0, aeson-1.5.1.0, aeson-1.5.0.0,
aeson-1.4.7.1, aeson-1.4.7.0, aeson-1.4.6.0, aeson-1.4.5.0, aeson-1.4.4.0,
aeson-1.4.3.0, aeson-1.4.2.0, aeson-1.4.1.0, aeson-1.4.0.0, aeson-1.3.1.1,
aeson-1.3.1.0, aeson-1.3.0.0 (has the same characteristics that caused the
previous version to fail: excluded by constraint '>=0.11 && <1.3 || >=0.9 &&
<0.10' from 'vgrep')
[__2] trying: aeson-1.2.4.0
[__3] next goal: th-abstraction (dependency of aeson)
[__3] rejecting: th-abstraction-0.3.2.0 (conflict: aeson =>
th-abstraction>=0.2.2 && <0.3)
[__3] skipping: th-abstraction-0.3.1.0, th-abstraction-0.3.0.0 (has the same
characteristics that caused the previous version to fail: excluded by
constraint '>=0.2.2 && <0.3' from 'aeson')
[__3] rejecting: th-abstraction-0.2.11.0 (conflict:
template-haskell==2.16.0.0/installed-2.16.0.0, th-abstraction =>
template-haskell>=2.5 && <2.15)
[__3] skipping: th-abstraction-0.2.10.0, th-abstraction-0.2.9.0,
th-abstraction-0.2.8.0, th-abstraction-0.2.7.0, th-abstraction-0.2.6.0,
th-abstraction-0.2.5.0, th-abstraction-0.2.4.0, th-abstraction-0.2.3.0,
th-abstraction-0.2.2.0, th-abstraction-0.2.1.0, th-abstraction-0.2.0.0,
th-abstraction-0.1.3.0, th-abstraction-0.1.2.1, th-abstraction-0.1.2.0,
th-abstraction-0.1.1.0, th-abstraction-0.1.0.0 (has the same characteristics
that caused the previous version to fail: excludes 'template-haskell' version
2.16.0.0)
[__3] fail (backjumping, conflict set: aeson, template-haskell,
th-abstraction)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: aeson, vgrep, template-haskell,
th-abstraction

This indicates that vgrep should be made compatible with the latest aeson. It's not as easy as updating the bounds on aeson though:

$ cabal install vgrep --constraint 'vgrep ==0.2.2.0' --allow-newer=aeson
<snip>

src/Vgrep/Ansi/Type.hs:51:10: error:
    • Could not deduce (Semigroup (Formatted attr))
        arising from the superclasses of an instance declaration
      from the context: (Eq attr, Monoid attr)
        bound by the instance declaration
        at src/Vgrep/Ansi/Type.hs:51:10-58
    • In the instance declaration for ‘Monoid (Formatted attr)’
   |
51 | instance (Eq attr, Monoid attr) => Monoid (Formatted attr) where
   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/Vgrep/Ansi/Type.hs:129:62: error:
    • Could not deduce (Semigroup (Formatted attr))
        arising from a use of ‘<>’
      from the context: (Eq attr, Monoid attr)
        bound by the type signature for:
                   fuse :: forall attr.
                           (Eq attr, Monoid attr) =>
                           Formatted attr -> Formatted attr -> Formatted attr
        at src/Vgrep/Ansi/Type.hs:123:1-84
    • In the third argument of ‘Format’, namely ‘(t <> t')’
      In the expression: Format (l + l') attr (t <> t')
      In a case alternative:
          (Format l attr t, Format l' attr' t')
            | attr' == attr -> Format (l + l') attr (t <> t')
    |
129 |         | attr' == attr             -> Format (l + l') attr (t <> t')
    |                                                              ^^^^^^^

(Possibly related to #52)

[sjakobi]

v0.2.3.0 is compatible. Thanks! :)

[sjakobi]

I just ran into this issue again. In response I've used my Hackage trustee powers to constrain vgrep < 0.1.5 to require vty < 5.15. See e.g. https://hackage.haskell.org/package/vgrep-0.1.4.1/revisions/.