I/O: writing

To save files we'll use the Io.Writer interface. I'm not going to explain in detail what is possible to do with it, because it has been recently introduced into the Zig standard library, it's a vast subject and I'm not familiar with it. So I'll stick to the minimum of informations to make our use case work.

Let's handle first the case where the filename is known, and we just want to save the current file.

We add another key-value pair to our status_messages string map:

    .{ "bufwrite", "\"{s}\" {d} lines, {d} bytes written" },

So that we'll print a message if the save is successful.

ioerr() and the error messages StringMap

Whenever a write operation fails, we'll handle the error in a helper function, ioerr():

/// Handle an error of type IoError by printing an error message, without
/// quitting the editor.
fn ioerr(e: *Editor, err: t.IoError) !void {
    try e.errorMessage(message.errors.get("ioerr").?, .{@errorName(err)});
    return;
}

As you can see, this function doesn't make the process terminate only because we couldn't save the file for some reason. Instead, it will print an error in the message area, with the name of the error.

IoError

The ioerr function accepts an argument of type IoError. This is an error union that we'll define in types:

///////////////////////////////////////////////////////////////////////////////
//
//                              Error sets
//
///////////////////////////////////////////////////////////////////////////////

/// Error set for both read and write operations.
pub const IoError = std.fs.File.OpenError
                 || std.fs.File.WriteError
                 || std.Io.Reader.Error
                 || std.Io.Writer.Error;

It includes errors for both reading and writing, because to write a file, we must also be able to open it, and also that can fail.

Error messages

We keep all these error messages we'll be using in message.zig, in another StringMap that we'll call errors:

const error_messages = .{
    .{ "ioerr", "Can't save! I/O error: {s}" },
};

pub const errors = std.StaticStringMap([]const u8).initComptime(error_messages);