Use `camelCaseFunctionNames` in generated files

[thesmartwon]

Use `camelCaseFunctionNames` in generated files

[travisstaloch]

I like the idea and would favor using lower camel case names in generated zig code. However, all of the other implementations I looked at used title camel case including go, cpp and python if i remember correctly. So I chose to follow them because its a little easier to compare generated code.

I'm not sure why this is a thing. I can see why the go impl does this as it follows the go style guide. But the cpp and python impls aren't following their style guides.

Maybe we could add a build or config option for changing the function casing? I would be glad to accept a PR for this. But I'd like to default to title case for now, at least until a day when this project is more trusted (known to work well) and comparing generated code shouldn't be necessary.

[clickingbuttons]

Hey @travisstaloch , would you accept a PR refactoring src/codegen.zig?

Serious issues

1. --no-gen-object-api still imports object API ...T types and Unpack functions
2. Property name collisions with unions can lead to generated code calling non-existent functions. For example:

union Type { Null, Int }
table Field { type: Type }

generates a non-existent call to rcv.Type_Type() instead of the correct rcv.TypeType():

pub fn UnpackTo(rcv: Field, t: *FieldT, __pack_opts: fb.common.PackOptions) !void {
    if (rcv.Type_()) |_tab| {
        t.type = try TypeT.Unpack(rcv.Type_Type(), _tab, __pack_opts);
    }
}

3. Object API optionals should be optional_field: ?T instead of optional_field: ?*T to prevent unnecessary allocation.
4. Add error printing on invalid codegen (useful for when Zig breaks codegenned syntax and for codegen devs)

Style issues

1. Remove _s from variable names. Zig purposefully disallows private struct members. Also, constants like __file_indent are already namespaced to the source file. Parameters like __builder can simply be renamed to builder.
2. Consistently use self: Self instead of inconsitently rcv: {type} and self: {type}
3. Add option for an index file with all generated types since there's a file generated per table/struct/union which can add up quickly.
4. As for the casing, I think a reason for Title over snake_case is to prevent parameter name shadowing like:

pub fn rcv(rcv: Field) bool {
    ...
}

This can of course be solved by renaming the parameter to rcv_ or something similar but adds another layer of complexity.

Sorry to hijack this issue, let me know if there's a better way to contact you. I'm happy to make all these changes.

[travisstaloch]

Hey @travisstaloch , would you accept a PR refactoring src/codegen.zig?

Sorry so long. Looked at this earler today and forgot to respond.

These all sound like legitimate problems to me and I would gladly accpt a PR. 👍

I've created #3 with the text from above. Lets discuss there