Fix "module defined in multiple files" with eval commands #214
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In #214, we had a situation where modules were loaded: ghci> :show targets Foo Bar Baz And then an eval comment in (e.g.) `Foo` causes the module to be added and explicitly interpreted by path: ghci> :add *src/Foo.hs Then, we have `Foo` loaded by name (`Foo`) and by path (`src/Foo.hs`), which triggers the dreaded bug. At the time I proposed this fix, correctly: > I think we can fix this by keeping track of how each module is added > to the session -- as a path or as a module name -- and then only using > that form going forward. I threaded some extra information to the `:show targets` parser to track if modules were listed as names or paths, **but then at the end of `Ghci::interpret_module` I would always insert the module into the target set as a `TargetKind::Path`,** meaning that the *next* time the comment was evaluated, the module would be loaded as a path, causing the error. https://github.com/MercuryTechnologies/ghciwatch/blob/dbba61bbdec9a86f97051b12647e51b7be4fd484/src/ghci/mod.rs#L698-L699 This fixes the bug and adds an `assert!` to fail faster and more obviously if it happens again.
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In #214, we had a situation where modules were loaded: ghci> :show targets Foo Bar Baz And then an eval comment in (e.g.) `Foo` causes the module to be added and explicitly interpreted by path: ghci> :add *src/Foo.hs Then, we have `Foo` loaded by name (`Foo`) and by path (`src/Foo.hs`), which triggers the dreaded bug. At the time I proposed this fix, correctly: > I think we can fix this by keeping track of how each module is added to the session — as a path or as a module name — and then only using that form going forward. I threaded some extra information to the `:show targets` parser to track if modules were listed as names or paths, **but then at the end of `Ghci::interpret_module` I would always insert the module into the target set as a `TargetKind::Path`,** meaning that the *next* time the comment was evaluated, the module would be loaded as a path, causing the error. https://github.com/MercuryTechnologies/ghciwatch/blob/dbba61bbdec9a86f97051b12647e51b7be4fd484/src/ghci/mod.rs#L698-L699 This fixes the bug and adds an `assert!` to fail faster and more obviously if it happens again. ## Prior art - #37 - #77 - #125 - #214
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Our favorite bug is back! We have a situation where
ghciwatchloads all the modules at the start of the session, so they're all loaded:Then, an eval command in (for example) module
Foois executed. To start with, the module is added and explicitly interpreted:Unfortunately, this always uses the module path (see #171), so if
ghciwatchwasn't the one to load the module (e.g. it was loaded at the start of the session), the module path and module name will conflict and lead tot he dreaded "module is defined in multiple files".See: https://gitlab.haskell.org/ghc/ghc/-/issues/13254#note_525037
Solution
I think we can fix this by keeping track of how each module is added to the session — as a path or as a module name — and then only using that form going forward.