On Fri, Sep 29, 2023 at 03:29:34PM +0200, Victor Toso wrote:
> Hi,
>
> On Thu, Sep 28, 2023 at 03:06:23PM +0100, Daniel P. Berrangé wrote:
> > On Wed, Sep 27, 2023 at 01:25:38PM +0200, Victor Toso wrote:
> > > This patch handles QAPI struct types and generates the equivalent
> > > types in Go. The following patch adds extra logic when a member of the
> > > struct has a Type that can take JSON Null value (e.g: StrOrNull in
> > > QEMU)
> > >
> > > The highlights of this implementation are:
> > >
> > > 1. Generating an Go struct that requires a @base type, the @base type
> > > fields are copied over to the Go struct. The advantage of this
> > > approach is to not have embed structs in any of the QAPI types.
> > > Note that embedding a @base type is recursive, that is, if the
> > > @base type has a @base, all of those fields will be copied over.
> > >
> > > 2. About the Go struct's fields:
> > >
> > > i) They can be either by Value or Reference.
> > >
> > > ii) Every field that is marked as optional in the QAPI specification
> > > are translated to Reference fields in its Go structure. This
> > > design decision is the most straightforward way to check if a
> > > given field was set or not. Exception only for types that can
> > > take JSON Null value.
> > >
> > > iii) Mandatory fields are always by Value with the exception of QAPI
> > > arrays, which are handled by Reference (to a block of memory) by
> > > Go.
> > >
> > > iv) All the fields are named with Uppercase due Golang's export
> > > convention.
> > >
> > > v) In order to avoid any kind of issues when encoding or decoding,
> > > to or from JSON, we mark all fields with its @name and, when it is
> > > optional, member, with @omitempty
> > >
> > > Example:
> > >
> > > qapi:
> > > | { 'struct': 'BlockdevCreateOptionsFile',
> > > | 'data': { 'filename': 'str',
> > > | 'size': 'size',
> > > | '*preallocation': 'PreallocMode',
> > > | '*nocow': 'bool',
> > > | '*extent-size-hint': 'size'} }
> > >
> > > go:
> > > | type BlockdevCreateOptionsFile struct {
> > > | Filename string `json:"filename"`
> > > | Size uint64 `json:"size"`
> > > | Preallocation *PreallocMode `json:"preallocation,omitempty"`
> > > | Nocow *bool `json:"nocow,omitempty"`
> > > | ExtentSizeHint *uint64 `json:"extent-size-hint,omitempty"`
> > > | }
> >
> > Note, 'omitempty' shouldn't be used on pointer fields, only
> > scalar fields. The pointer fields are always omitted when nil.
>
> 'omitempty' should be used with pointer fields unless you want to
> Marshal JSON Null, which is not the expected output.
Oh doh, did't notice that.
With regards,
Daniel
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