fix: enable field removal for destination metadata/delivery_metadata

[alexluong]

Destination Field Removal Fix

Problem

Impossible to clear filter, metadata, or delivery_metadata on destination update by sending {}.

• Server: metadata/delivery_metadata used merge semantics — sending {} was a no-op
• Go SDK: json:",omitempty" drops empty maps before serialization, so {} never reaches the server

Server Fix

Changed metadata and delivery_metadata from merge to full replacement (matching how filter already worked).

Input	Behavior
Omitted / null	No change
{}	Clears the field
{"key": "val"}	Replaces entirely

config and credentials intentionally keep merge semantics.

SDK Status

SDK	Can send {} to clear?	Breaking changes?
TypeScript	✅ Works	None
Python	✅ Works	None
Go	❌ No	See below
Portal	✅ Works	N/A

All 148 TS tests and 11 Python tests pass.

Go SDK Limitation

Go's omitempty strips empty maps before serialization — {} becomes indistinguishable from "not sent".

Speakeasy has a nullableOptionalWrapper flag that generates three-state OptionalNullable[T] types (not set vs null vs value). This would solve it, but the flag is global and all-or-nothing — it wraps ~30+ fields across the entire SDK (Create, Response, Event, Attempt, Tenant), not just the update structs.

For example, with the flag enabled, the update struct changes from:

// Before (current) — empty map is silently dropped by omitempty
type DestinationUpdateWebhook struct {
    Filter           map[string]any    `json:"filter,omitempty"`
    DeliveryMetadata map[string]string `json:"delivery_metadata,omitempty"`
    Metadata         map[string]string `json:"metadata,omitempty"`
}

// After (with flag) — three-state: not set, null, or value (including {})
type DestinationUpdateWebhook struct {
    Filter           optionalnullable.OptionalNullable[map[string]any]    `json:"filter,omitempty"`
    DeliveryMetadata optionalnullable.OptionalNullable[map[string]string] `json:"delivery_metadata,omitempty"`
    Metadata         optionalnullable.OptionalNullable[map[string]string] `json:"metadata,omitempty"`
}

This is what we want — but the same wrapping also applies to every other nullable field: Tenant.Metadata, Event.Metadata, Attempt.ResponseData, Attempt.Event, DestinationCreateWebhook.Filter, all response structs, etc. (~30+ fields total).

DX impact on Go SDK usage

Creating a destination (current):

sdk.Destinations.Create(ctx, tenantID, components.DestinationCreateWebhook{
    Type:   "webhook",
    Topics: components.TopicsArrayOfStrings([]string{"user.created"}),
    Config: components.WebhookConfig{URL: "https://example.com/webhook"},
    Metadata: map[string]string{"team": "platform"},
})

Creating a destination (with flag):

sdk.Destinations.Create(ctx, tenantID, components.DestinationCreateWebhook{
    Type:   "webhook",
    Topics: components.TopicsArrayOfStrings([]string{"user.created"}),
    Config: components.WebhookConfig{URL: "https://example.com/webhook"},
    Metadata: optionalnullable.Of(map[string]string{"team": "platform"}),
})

Clearing metadata on update (with flag):

sdk.Destinations.Update(ctx, tenantID, destID, components.DestinationUpdateWebhook{
    Metadata: optionalnullable.Of(map[string]string{}), // sends {} → clears
})

Reading from response (with flag):

dest, _ := sdk.Destinations.Get(ctx, tenantID, destID)
// Before: dest.Metadata["team"]
// After:  dest.Metadata.Value()["team"]  (must unwrap OptionalNullable first)

Every nullable field across the SDK requires wrapping/unwrapping — not just the update fields we care about.

What we tried to scope it to update fields only

• Go-specific OpenAPI overlay converting only update fields to 3.1-style nullable (type: ["object", "null"]) — Speakeasy doesn't distinguish 3.0 vs 3.1, still wraps everything
• Searched for per-field extension (x-speakeasy-nullable etc.) — doesn't exist in Speakeasy's 52 extensions

Note: Go SDK currently does not support sending null either — only omitted and value. This is a current Outpost limitation, not a design decision. If we want to support explicit null semantics in the future, we'd need to explore the OptionalNullable wrapper regardless.

Options:

1. Document as Go limitation — users who need to clear fields use raw HTTP
2. Accept breaking change — flip the flag, bump Go SDK major version
3. Engage Speakeasy — request per-field nullable control

Test plan

• Unit tests: 12 tests in destination_handlers_test.go (filter/metadata/delivery_metadata: replaced not merged, cleared with {}, unchanged when omitted)
• SDK e2e tests (TS): 11 field removal tests + 148 total passing
• SDK e2e tests (Python): 11 field removal tests passing
• Pre-existing test fixes: events.test.ts and tenants.test.ts updated for PageIterator response shape

🤖 Generated with Claude Code