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Update HACKING.md

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Julian Ospald 2016-05-30 14:37:15 +02:00
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@ -61,6 +61,8 @@ This leads to the following benefits:
* we can reason about filepaths and rely on them to be valid (don't confuse that with "they exist") * we can reason about filepaths and rely on them to be valid (don't confuse that with "they exist")
* filepath functions like `(</>)` are now predictable and safe in contrast to the version from the `filepath` package * filepath functions like `(</>)` are now predictable and safe in contrast to the version from the `filepath` package
The [hpath](https://hackage.haskell.org/package/hpath) library does exactly that for us.
The only problem with this approach is that most libraries are still String The only problem with this approach is that most libraries are still String
based. Some provide dedicated `Foo.ByteString` modules though, but it based. Some provide dedicated `Foo.ByteString` modules though, but it
might be necessary to fork libraries. might be necessary to fork libraries.
@ -84,17 +86,10 @@ the call stack at point `b` in time, when the file information in memory
could already be out of date. There are two approaches to make this less could already be out of date. There are two approaches to make this less
sucky: sucky:
* use the hinotify library on GUI level to refresh the view (and the File representation in memory) whenever the contents of a directory changes * use the hinotify library on GUI level to refresh the view (and the File representation in memory) whenever the contents of a directory changes
* when we stuff something into the copy buffer, it is not saved as type `File a`, but as `Path Abs`... when the operation is finalized via `runFileOp`, then the file at the given path is read and the copy/move/whatnot function carried out immediately * when we stuff something into the copy buffer, it is not saved as type `File a`, but as `Path Abs`... when the operation is finalized then the file at the given path is read and the copy/move/whatnot function carried out immediately
This means we should only interact with the `HSFM.FileSystem.FileOperation`
module via the operation data types `FileOperation`, `Copy` and `Move` and
the `runFileOp` function. This doesn't completely solve the problem, but for
the rest we have to trust the posix functions to throw the proper exceptions.
In addition, we don't use the `directory` package, which is dangerous In addition, we don't use the `directory` package, which is dangerous
and broken. Instead, we implement our own low-level wrappers around and broken. Instead, we use the [HPath.IO](https://hackage.haskell.org/package/hpath/docs/HPath-IO.html).
the posix functions, so we have proper control over the internals
and know the possible exceptions.
### Exception handling ### Exception handling
@ -102,7 +97,7 @@ Exceptions are good. We don't want to wrap everything in Maybe/Either types
unless we want to handle failure immediately. Otherwise we need to make unless we want to handle failure immediately. Otherwise we need to make
sure that at least at some point IOExceptions are caught and visualized sure that at least at some point IOExceptions are caught and visualized
to the user. This is often done via e.g. `withErrorDialog` which catches to the user. This is often done via e.g. `withErrorDialog` which catches
`IOException` and `FmIOException`. `IOException` and [HPathIOException](https://hackage.haskell.org/package/hpath/docs/HPath-IO-Errors.html#t:HPathIOException).
It's also important to clean up stuff like filedescriptors via It's also important to clean up stuff like filedescriptors via
functions like `bracket` directly in our low-level code in case functions like `bracket` directly in our low-level code in case