REPL returns list of all imported names when operator completion requested

When querying completions for operators GHCi returns a list containing all imported names rather than suitable completions.

For example, if you simply start GHCi and run :complete repl ">>" command it will give you all names from base and Prelude. Then if you import something else, for example :m +Data.Text, the result of query will contain names from Data.Text also.

In case of projects (cabal repl) things are worst, because returned list contains all names imported project-wise and it could be really huge.

GHCi behaves similarly with following queries:

:complete repl "(>>"
:complete repl "Prelude.>>"
:complete repl "Prelude.(>>"

I only tested this on OS X 10.9, GHC 7.8.4

mentioned in issue #9996 (closed)

changed weight to 5

added GHCi Tbug Trac import labels

Same here on Windows with GHC 7.8.3.

assigned to @trac-thomie

Also reported as #9996 (closed).

The problem comes from using the default word_break_chars when completing identifiers in ghc/ghc/InteractiveUI.hs:

 -- We initialize readline (in the interactiveUI function) to use
 -- word_break_chars as the default set of completion word break characters.
 -- This can be overridden for a particular command (for example, filename
 -- expansion shouldn't consider '/' to be a word break) by setting the third
 -- entry in the Command tuple above.
 --
 -- NOTE: in order for us to override the default correctly, any custom entry
 -- must be a SUBSET of word_break_chars.
 word_break_chars :: String
 word_break_chars = let symbols = "!#$%&*+/<=>?@\\^|-~"
                        specials = "(),;[]`{}"
                        spaces = " \t\n"
                    in spaces ++ specials ++ symbols
 
wrapIdentCompleter = wrapCompleter word_break_chars

Trac metadata

Trac field	Value
Related	→ #9996 (closed)

My little investigation lead me to completeQuotedWord function, but I can't follow any further now because I can't find where it comes from:

completeCmd [1] -> -> [2] -> ghciCompleteWord [3] -> [4] -> completeExpression [5]

completeExpression = completeQuotedWord (Just '\\') "\"" listFiles
                        completeIdentifier

[1]:https://github.com/ghc/ghc/blob/d20031d4c88b256cdae264cb05d9d850e973d956/ghc/InteractiveUI.hs#L2481 [2]:https://github.com/ghc/ghc/blob/d20031d4c88b256cdae264cb05d9d850e973d956/ghc/InteractiveUI.hs#L2484 [3]:https://github.com/ghc/ghc/blob/d20031d4c88b256cdae264cb05d9d850e973d956/ghc/InteractiveUI.hs#L2528 [4]:https://github.com/ghc/ghc/blob/d20031d4c88b256cdae264cb05d9d850e973d956/ghc/InteractiveUI.hs#L2535 [5]:https://github.com/ghc/ghc/blob/d20031d4c88b256cdae264cb05d9d850e973d956/ghc/InteractiveUI.hs#L2639

The problem comes from using the default word_break_chars

Oh, so I suppose potential solution is to check if prefix to be completed starts with operator symbol, and if the case do not use wrapIdentCompleter in completeIdentifier.

changed the description

assigned to @trac-Geraldus and unassigned @trac-thomie

Trac metadata

Trac field	Value
Differential revisions	- → D1058

mentioned in commit b3eb8fad

mentioned in issue #11483

Update.

This works:

Prelude> (☀☀) _ _ = ()
Prelude> x1 ☀<TAB>

This doesn't work:

Prelude> (☀☀) _ _ = ()
Prelude> x1☀<TAB>

A space is needed between the variable and the operator for completion to work.

To solve this nicely requires adding a function to haskeline, similar to completeWord, but which takes a predicate function instead of a list of escape characters.

The tests T10576a and T10576b are marked expect_broken for this issue.

Trac metadata

Trac field	Value
Test case	- → ghci/prog017 ghci/scripts/T10576a T10576b

mentioned in issue #12008

added incorrect runtime result label

added broken test label

added Pnormal label

mentioned in merge request !4941 (closed)

changed milestone to %9.2.1

assigned to @RolandSenn and unassigned @trac-Geraldus

mentioned in commit 268696d5

mentioned in commit 072fbe10

mentioned in commit 793dcb3d

Commit 793dcb3d in MR 4941 fixed this issue.

closed