In previous releases, passing a `nil` value as an FS config
did not cause any error. However, in 1.0.0-rc.1 this leads
to the creation of an invalid `adapter{fs: nil}`, which
eventually leads to a panic (nil):
(f *FileEntry) Stat(st *platform.Stat_t) =>
(r *lazyDir) file() =>
r.fs.OpenFile(".", os.O_RDONLY, 0)
with fs == nil
The backwards-compatible fix is to make Adapt()
return UnimplementedFS, and ensuring `nil` is a valid value
that config is able to handle.
However, we may want to consider returning an error somewhere,
because configuring a nil FS may be unintended.
Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>
This adds a new top-level type FSConfig, which is configured via
`ModuleConfig.WithFSConfig(fcfg)`. This implements read-only and
read-write directory mounts, something not formally supported before. It
also implements `WithFS` which adapts a normal `fs.FS`. For convenience,
we retain the old `ModuleConfig.WithFS` signature so as to not affect
existing users much. A new configuration for our emerging raw
filesystem, `FSConfig.WithSysfs()` will happen later without breaking
this API.
Here's an example:
```
moduleConfig = wazero.NewModuleConfig().
// Make the current directory read-only accessible to the guest.
WithReadOnlyDirMount(".", "/")
// Make "/tmp/wasm" accessible to the guest as "/tmp".
WithDirMount("/tmp/wasm", "/tmp")
```
Signed-off-by: Adrian Cole <adrian@tetrate.io>
