keep unimplemented notifications from closing connections

[zchee]

Summary

This PR fixes the default unimplemented LSP stubs so unhandled notifications are ignored instead of failing the JSON-RPC connection, while preserving method not found responses for unhandled requests.

It also cleans up the generated protocol surface around InitializeParams by flattening private _-prefixed meta-model bases into their public referrers, adds explicit constructors for Nullable[T], and tightens the structure-flattening generator so duplicate inherited fields/embeds are emitted only once.

Why

A JSON-RPC notification has no response slot. Returning a non-nil error from an unimplemented notification handler causes the dispatcher to treat that error as a connection-level failure. That made embedders of UnimplementedServer or UnimplementedClient lose the connection when a peer sent a notification they did not override, such as early window/logMessage traffic.

The LSP metaModel also exposes private helper structures such as _InitializeParams. Emitting those as public Go types leaks implementation detail into the API and adds avoidable indirection on initialize encoding/decoding.

What changed

• Return nil from unimplemented notification stubs so notifications are ignored per LSP/JSON-RPC semantics.
• Keep errNotImplemented for request stubs so peers still receive classified method not found responses.
• Add integration coverage proving an unimplemented client survives a server-sent notification and remains usable for later requests.
• Flatten _-prefixed meta-model structures into public referrers and emit empty structs as struct{}.
• Deduplicate inherited fields and embeds during recursive private-base flattening.
• Add NewNullable(v) and NullNullable[T]() constructors for the value and explicit-null states of Nullable[T].
• Keep cleanup-only review noise out of the generated/nullable changes without altering generated output.

Impact

Consumers can embed UnimplementedServer or UnimplementedClient and override only the methods they support without unhandled notifications tearing down the connection. Generated initialize types are also cleaner and avoid exposing private meta-model helper types.

Validation

• go test ./...
• go vet ./...
• go tool golangci-lint run ./... (0 issues)

[codecov]

Codecov Report

❌ Patch coverage is 96.77419% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.2%. Comparing base (2d08f2b) to head (dbfd534).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/genlsp/emit.go	96.6%	2 Missing ⚠️

@@          Coverage Diff          @@
##            main     #60   +/-   ##
=====================================
  Coverage   85.1%   85.2%           
=====================================
  Files         27      27           
  Lines       6077    6135   +58     
=====================================
+ Hits        5177    5230   +53     
- Misses       900     905    +5     

Flag	Coverage Δ
Linux-ARM64	85.2% <96.7%> (+<0.1%)	⬆️
Linux-X64	87.5% <95.9%> (+<0.1%)	⬆️

Files with missing lines	Coverage Δ
nullable.go	90.9% <100.0%> (+0.9%)	⬆️
protocol.go	100.0% <ø> (ø)
internal/genlsp/emit.go	90.9% <96.6%> (+<0.1%)	⬆️

[zchee]

/gemini review

[gemini-code-assist]

Code Review

This pull request flattens underscore-prefixed private base structures (such as _InitializeParams) directly into their public referrers during LSP code generation, eliminating the need to emit them as separate types. It also updates UnimplementedServer and UnimplementedClient notification methods to return nil instead of errNotImplemented to prevent connection teardown when notifications are unhandled, supported by a new integration test. Additionally, helper constructors NewNullable and NullNullable are introduced. The review feedback suggests tracking seenEmbeds and seenFields at the public structure level and passing them into inlineContribution to prevent duplicate fields or embeds when a public structure embeds multiple private bases or defines overlapping fields.

[zchee]

/gemini review

[gemini-code-assist]

Code Review

This pull request flattens private base structures (prefixed with an underscore) directly into their public referrers within the LSP generator, simplifying the generated Go structs and removing unnecessary private types. Additionally, it updates un-overridden notification methods in UnimplementedServer and UnimplementedClient to return nil instead of errNotImplemented, preventing connection teardowns when unhandled notifications are received. A review comment correctly identifies a potential infinite recursion risk in the recursive flatten function of the generator and suggests adding cycle detection.

[gemini-code-assist]

To prevent potential infinite recursion and stack overflow in case of cyclic dependencies in the meta-model structures (e.g., if a private base structure directly or indirectly references itself), it is safer to implement cycle detection using a visited map within the recursive flatten function.

	visited := make(map[string]bool)
	var flatten func(structure *Structure)
	flatten = func(structure *Structure) {
		if visited[structure.Name] {
			return
		}
		visited[structure.Name] = true