System.FS.Sim.Error

Introduce possibility of errors

Alternative to simErrorHasFS that creates TVars internally.

Runs a computation provided an Errors and an initial MockFS, producing a result and the final state of the filesystem.

Execute the next action using the given Errors. After the action is finished, the previous Errors are restored.

An ErrorStream is a possibly infinite Stream of (Maybe) FsErrorTypes.

Nothing indicates that there is no error.

Each time the ErrorStream is used (see runErrorStream), the first element (Nothing in case the list is empty) is taken from the list and an ErrorStream with the remainder of the list is returned. The first element represents whether an error should be returned or not.

An FsError consists of a number of fields: fsErrorType, a fsErrorPath, etc. Only the first fields is interesting. Therefore, we only generate the FsErrorType. The FsErrorType will be used to construct the actual FsError.

ErrorStream for reading bytes from a file: an error or a partial get.

ErrorStream for writing bytes to a file: an error and possibly some corruption, or a partial write.

A Partial p, where p > 0, is a number representing how many fewer bytes should be read or written than requested.

Given a requested number of bytes to read/write, compute a partial number of bytes to read/write.

We subtract p from the number of requested bytes. If that would result in 0 requested bytes or less, we request 1 byte. If the number of requested bytes was already 0, we can't simulate a partial read so we return 0 again.

Like partialiseByteCount, but for Word64.

Given a bytestring that is requested to be written to disk, use partialiseByteCount to compute a partial bytestring.

Model possible corruptions that could happen to a hPutSome call.

Apply the PutCorruption to the ByteString.

If the bytestring is substituted by corrupt junk, then the output bytestring might be larger than the input bytestring.

Error streams for the methods of the HasFS type class.

An ErrorStream is provided for each method of the HasFS type class. This ErrorStream will be used to generate potential errors that will be thrown by the corresponding method.

For hPutSome, an ErrorStreamWithCorruption is provided to simulate corruption.

An Errors is used in conjunction with SimErrorFS, which is a layer on top of SimFS that simulates methods throwing FsErrors.

Return True if all streams are empty (null).

Generator for Errors that allows some things to be disabled.

This is needed by the VolatileDB state machine tests, which try to predict what should happen based on the Errors, which is too complex sometimes.

Use the given ErrorStream for each field/method. No corruption of hPutSome.