feat(api-docs): generate OpenAPI components/schemas from Go structs

A new emit_jsonschema.go walks the same allow-listed structs as the zod/types/examples emitters and writes generated/schemas.ts (SCHEMAS). build-openapi mounts it under components.schemas and points each typed response obj at a $ref instead of an untyped {} blob, so Swagger renders real models and openapi-generator can emit clients.

Also add a vitest guard that safeParses every EXAMPLES entry against its generated zod schema, reviving the previously unused generated/zod.ts and catching drift between the example and schema emitters.

tools/openapigen/emit_jsonschema.go

@@ -0,0 +1,190 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+func emitJSONSchema(w io.Writer, schemas []Schema, aliases []Alias) error {
+	byName := make(map[string]Schema, len(schemas))
+	for _, s := range schemas {
+		byName[s.Name] = s
+	}
+	aliasByName := make(map[string]Alias, len(aliases))
+	for _, a := range aliases {
+		aliasByName[a.Name] = a
+	}
+
+	gen := &schemaGen{byName: byName, aliasByName: aliasByName}
+
+	out := make(map[string]any, len(schemas))
+	for _, s := range schemas {
+		out[s.Name] = gen.objectSchema(s)
+	}
+
+	payload, err := json.MarshalIndent(out, "", "  ")
+	if err != nil {
+		return err
+	}
+	if _, err := fmt.Fprintln(w, examplesHeader); err != nil {
+		return err
+	}
+	if _, err := fmt.Fprintf(w, "export const SCHEMAS: Record<string, unknown> = %s;\n", payload); err != nil {
+		return err
+	}
+	return nil
+}
+
+type schemaGen struct {
+	byName      map[string]Schema
+	aliasByName map[string]Alias
+}
+
+func (g *schemaGen) objectSchema(s Schema) map[string]any {
+	props := make(map[string]any, len(s.Fields))
+	var required []string
+	for _, f := range s.Fields {
+		props[f.JSONName] = g.fieldSchema(f)
+		if !f.Optional {
+			required = append(required, f.JSONName)
+		}
+	}
+	obj := map[string]any{"type": "object", "properties": props}
+	if len(required) > 0 {
+		sort.Strings(required)
+		obj["required"] = required
+	}
+	if s.Doc != "" {
+		obj["description"] = s.Doc
+	}
+	return obj
+}
+
+func (g *schemaGen) fieldSchema(f Field) map[string]any {
+	sch := g.typeSchema(f.Type)
+	if ref, ok := sch["$ref"]; ok {
+		if f.Doc == "" && f.Example == "" {
+			return sch
+		}
+		wrap := map[string]any{"allOf": []any{map[string]any{"$ref": ref}}}
+		if f.Doc != "" {
+			wrap["description"] = f.Doc
+		}
+		if f.Example != "" {
+			wrap["example"] = coerceExample(f.Example, baseKind(f.Type))
+		}
+		return wrap
+	}
+	applyConstraints(sch, f.Type, f.Validate)
+	if f.Doc != "" {
+		sch["description"] = f.Doc
+	}
+	if f.Example != "" {
+		sch["example"] = coerceExample(f.Example, baseKind(f.Type))
+	}
+	return sch
+}
+
+func (g *schemaGen) typeSchema(t TypeRef) map[string]any {
+	switch t.Kind {
+	case KindString:
+		if t.Name == "datetime" {
+			return map[string]any{"type": "string", "format": "date-time"}
+		}
+		return map[string]any{"type": "string"}
+	case KindInt:
+		return map[string]any{"type": "integer"}
+	case KindNumber:
+		return map[string]any{"type": "number"}
+	case KindBool:
+		return map[string]any{"type": "boolean"}
+	case KindArray:
+		return map[string]any{"type": "array", "items": g.typeSchema(*t.Element)}
+	case KindMap:
+		return map[string]any{"type": "object", "additionalProperties": g.typeSchema(*t.Value)}
+	case KindAny, KindUnknown, KindRaw:
+		return map[string]any{}
+	case KindRef:
+		if t.Name == "nullable" {
+			inner := g.typeSchema(*t.Inner)
+			if ref, ok := inner["$ref"]; ok {
+				return map[string]any{"nullable": true, "allOf": []any{map[string]any{"$ref": ref}}}
+			}
+			inner["nullable"] = true
+			return inner
+		}
+		if alias, ok := g.aliasByName[t.Name]; ok {
+			return g.typeSchema(alias.Underlying)
+		}
+		if _, ok := g.byName[t.Name]; ok {
+			return map[string]any{"$ref": "#/components/schemas/" + t.Name}
+		}
+		return map[string]any{}
+	}
+	return map[string]any{}
+}
+
+func applyConstraints(sch map[string]any, t TypeRef, rules []ValidateRule) {
+	base := baseKind(t)
+	numeric := base.Kind == KindInt || base.Kind == KindNumber
+	str := base.Kind == KindString
+	for _, r := range rules {
+		switch r.Name {
+		case "gte":
+			if numeric {
+				sch["minimum"] = coerceExample(r.Param, base)
+			}
+		case "lte":
+			if numeric {
+				sch["maximum"] = coerceExample(r.Param, base)
+			}
+		case "gt":
+			if numeric {
+				sch["minimum"] = coerceExample(r.Param, base)
+				sch["exclusiveMinimum"] = true
+			}
+		case "lt":
+			if numeric {
+				sch["maximum"] = coerceExample(r.Param, base)
+				sch["exclusiveMaximum"] = true
+			}
+		case "min":
+			if numeric {
+				sch["minimum"] = coerceExample(r.Param, base)
+			} else if str {
+				if n, err := strconv.Atoi(r.Param); err == nil {
+					sch["minLength"] = n
+				}
+			}
+		case "max":
+			if numeric {
+				sch["maximum"] = coerceExample(r.Param, base)
+			} else if str {
+				if n, err := strconv.Atoi(r.Param); err == nil {
+					sch["maxLength"] = n
+				}
+			}
+		case "oneof":
+			vals := strings.Fields(r.Param)
+			if len(vals) > 0 {
+				enum := make([]any, len(vals))
+				for i, v := range vals {
+					enum[i] = v
+				}
+				sch["enum"] = enum
+			}
+		case "email":
+			if str {
+				sch["format"] = "email"
+			}
+		case "url":
+			if str {
+				sch["format"] = "uri"
+			}
+		}
+	}
+}

tools/openapigen/main.go

@@ -106,6 +106,10 @@ func run(root, outDir string) error {
 	if err := emitExamples(examplesBuf, schemas, aliases); err != nil {
 		return err
 	}
+	schemasBuf := &bytes.Buffer{}
+	if err := emitJSONSchema(schemasBuf, schemas, aliases); err != nil {
+		return err
+	}
 
 	if err := os.WriteFile(filepath.Join(target, "zod.ts"), zodBuf.Bytes(), 0o644); err != nil {
 		return err
@@ -116,6 +120,9 @@ func run(root, outDir string) error {
 	if err := os.WriteFile(filepath.Join(target, "examples.ts"), examplesBuf.Bytes(), 0o644); err != nil {
 		return err
 	}
+	if err := os.WriteFile(filepath.Join(target, "schemas.ts"), schemasBuf.Bytes(), 0o644); err != nil {
+		return err
+	}
 
 	fmt.Printf("openapigen: wrote %d schemas to %s\n", len(schemas), target)
 	return nil