fix: preserve Go allOf object composition

docs/src/SUMMARY.md

@@ -7,6 +7,7 @@
 - [Multipart and Binary Bodies](multipart_and_binary.md)
 - [Response Headers](response_headers.md)
 - [Rust Generator Configuration](rust_config.md)
+- [Go Generator Configuration](go_config.md)
 - [TypeScript Generator Configuration](ts_config.md)
 - [Python Generator Configuration](python_config.md)
 - [Java Generator Configuration](java_config.md)

docs/src/go_config.md

@@ -0,0 +1,58 @@
+# Go Generator Configuration
+
+```toml
+[go-http]
+module_path = "example.com/sdk"
+all_of_strategy = "composed"
+```
+
+## Object and map composition
+
+The default `composed` policy retains named object members as embedded Go fields
+and gives anonymous map members named storage such as `AdditionalProperties`.
+Generated JSON methods combine the members into one flat wire object rather
+than inheriting one embedded member's JSON methods and losing its siblings.
+
+```go
+value := models.Pair{
+    Base: models.Base{KnownField: "fixed"},
+    Other: models.Other{OtherField: 7},
+}
+// json.Marshal(value): {"known_field":"fixed","other_field":7}
+```
+
+Existing named member entrypoints and promoted fields remain available. Repeated
+member names or map-storage collisions receive numeric suffixes. Aliases and
+nested object compositions are followed without rewriting ordinary model codecs.
+
+On reading, each member receives its own declared keys and globally unknown keys.
+A sibling's declared keys are not duplicated into extension storage, so editing a
+named field does not leave stale values in a map member. Typed members retain their
+native `encoding/json` behavior. If member writes produce different JSON encodings
+for the same key, marshaling returns an error instead of silently overwriting data.
+
+This is not a complete JSON Schema validator. It uses retained IR object facts and
+conservative representation compatibility; ordinary member validation, optional
+fields, null behavior and dynamic `any` number conversion remain unchanged.
+In particular, `any` entries still follow Go's native floating-point conventions.
+It does not infer missing shared-lowering facts or redesign ordinary dictionary
+codecs.
+
+## Raw escape hatch
+
+Set `all_of_strategy = "raw"` to emit every intersection as an alias of
+`json.RawMessage`, preserving JSON kinds, nulls and exact numeric literals without
+typed member selection. The same raw representation is the default fallback for
+non-object intersections, unproductive composition cycles and object/map types
+that cannot be conservatively composed. No unconditional generation error or
+invalid anonymous-map embedding is introduced for these shapes.
+
+```bash
+openapi-nexus generate --input api.yaml --output sdk --generators go-http \
+  --generator-config go-http.all_of_strategy=raw
+```
+
+Raw values intentionally do not enforce intersection constraints. Use them when
+wire preservation is more useful than inferred typed composition. This policy
+does not change untagged unions, ordinary objects, other generators or generated
+dependencies.

just/golden-go.just

@@ -7,5 +7,13 @@ set working-directory := '..'
     UPDATE_GOLDEN=1 cargo test --test golden_tests_go_http -- --nocapture
 
 # Compile-check Go goldens with go build
-@build:
+@build: test
     ./scripts/golden-build-go.sh
+
+# Generate fresh dependencies before ordinary Go consumer execution.
+@prepare:
+    bash ./scripts/generate-go-client-fixtures.sh
+
+@test: prepare
+    go -C tests/generated-clients/go/composition test ./...
+    go -C tests/generated-clients/go/raw test ./...

scripts/generate-go-client-fixtures.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+root="$(cd "$(dirname "$0")/.." && pwd)"
+project="$root/tests/generated-clients/go"
+while read -r name fixture strategy; do
+  case "$name" in
+    ""|\#*) continue ;;
+    *[!a-zA-Z0-9_-]*) echo "invalid fixture name: $name" >&2; exit 1 ;;
+  esac
+  output="$project/generated/$name"
+  options=(--config "$root/tests/generated-clients/config.toml"
+    --input "$root/tests/fixtures/$fixture" --output "$output" --generators go-http)
+  if [ -n "$strategy" ]; then
+    case "$strategy" in
+      composed|raw) ;;
+      *) echo "invalid allOf strategy: $strategy" >&2; exit 1 ;;
+    esac
+    options+=(--generator-config "go-http.all_of_strategy=$strategy")
+  fi
+  # Only these fixed, ignored fixture output directories are disposable.
+  rm -rf "$output"
+  cargo run --quiet --manifest-path "$root/Cargo.toml" --bin openapi-nexus -- generate "${options[@]}"
+done < "$project/fixtures.txt"

src/generators/go/http/codegen.rs

@@ -55,6 +55,7 @@ impl GoHttpCodeGenerator {
             &module_path,
             &header,
             &request_inputs,
+            self.config.all_of_strategy,
         )?);
 
         // APIs