oweb: make DecodeUserJSON take a field name

This allows for better error messages when decoding fails. For example,
instead of:

    {"code":"invalid_json","message":"unexpected end of JSON input"}

We now get:

    {"code":"invalid_json","field":"manifest","message":"unexpected end of JSON input"}

api/api.go

@@ -104,3 +104,7 @@ func (s *Server) handlePush(_ http.ResponseWriter, r *http.Request) error {
 	return err
 
 }
+
+func (s *Server) handlePull(w http.ResponseWriter, r *http.Request) error {
+	return oweb.ErrNotFound
+}

oweb/oweb.go

@@ -63,20 +63,21 @@ func Serve(h HandlerFunc, w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-func DecodeUserJSON[T any](r io.Reader) (*T, error) {
+func DecodeUserJSON[T any](field string, r io.Reader) (*T, error) {
 	v, err := DecodeJSON[T](r)
+	if err == nil {
+		return v, nil
+	}
+	var msg string
 	var e *json.SyntaxError
 	if errors.As(err, &e) {
-		return nil, &ollama.Error{Code: "invalid_json", Message: e.Error()}
+		msg = e.Error()
 	}
 	var se *json.UnmarshalTypeError
 	if errors.As(err, &se) {
-		return nil, &ollama.Error{
+		msg = fmt.Sprintf("%s (%q) is not a %s", se.Field, se.Value, se.Type)
-			Code:    "invalid_json",
-			Message: fmt.Sprintf("%s (%q) is not a %s", se.Field, se.Value, se.Type),
 	}
-	}
+	return nil, Mistake("invalid_json", field, msg)
-	return v, err
 }
 
 func DecodeJSON[T any](r io.Reader) (*T, error) {

registry/apitypes.go

@@ -1,5 +1,7 @@
 package registry
 
+import "encoding/json"
+
 type Manifest struct {
 	Layers []Layer `json:"layers"`
 }
@@ -11,7 +13,8 @@ type Layer struct {
 }
 
 type PushRequest struct {
-	Manifest Manifest `json:"manifest"`
+	Ref      string `json:"ref"`
+	Manifest json.RawMessage
 }
 
 type Requirement struct {

registry/client.go

@@ -2,7 +2,6 @@ package registry
 
 import (
 	"context"
-	"encoding/json"
 	"io"
 	"net/http"
 
@@ -11,14 +10,20 @@ import (
 
 type Client struct {
 	BaseURL    string
+	HTTPClient *http.Client
+}
+
+func (c *Client) oclient() *ollama.Client {
+	return (*ollama.Client)(c)
 }
 
 // Push pushes a manifest to the server.
 func (c *Client) Push(ctx context.Context, ref string, manifest []byte) ([]Requirement, error) {
 	// TODO(bmizerany): backoff
-	v, err := ollama.Do[PushResponse](ctx, "POST", c.BaseURL+"/v1/push/"+ref, struct {
+	v, err := ollama.Do[PushResponse](ctx, c.oclient(), "POST", "/v1/push", &PushRequest{
-		Manifest json.RawMessage `json:"manifest"`
+		Ref:      ref,
-	}{manifest})
+		Manifest: manifest,
+	})
 	if err != nil {
 		return nil, err
 	}

registry/server.go

@@ -2,6 +2,7 @@
 package registry
 
 import (
+	"bytes"
 	"cmp"
 	"context"
 	"errors"
@@ -34,16 +35,16 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 func (s *Server) serveHTTP(w http.ResponseWriter, r *http.Request) error {
 	switch {
-	case strings.HasPrefix(r.URL.Path, "/v1/push/"):
+	case strings.HasPrefix(r.URL.Path, "/v1/push"):
 		return s.handlePush(w, r)
-	case strings.HasPrefix(r.URL.Path, "/v1/pull/"):
+	case strings.HasPrefix(r.URL.Path, "/v1/pull"):
 		return s.handlePull(w, r)
 	}
 	return oweb.ErrNotFound
 }
 
 func (s *Server) handlePush(w http.ResponseWriter, r *http.Request) error {
-	pr, err := oweb.DecodeUserJSON[PushRequest](r.Body)
+	pr, err := oweb.DecodeUserJSON[PushRequest]("", r.Body)
 	if err != nil {
 		return err
 	}
@@ -53,9 +54,14 @@ func (s *Server) handlePush(w http.ResponseWriter, r *http.Request) error {
 		Secure: false,
 	})
 
+	m, err := oweb.DecodeUserJSON[Manifest]("manifest", bytes.NewReader(pr.Manifest))
+	if err != nil {
+		return err
+	}
+
 	// TODO(bmizerany): parallelize
 	var requirements []Requirement
-	for _, l := range pr.Manifest.Layers {
+	for _, l := range m.Layers {
 		if l.Size == 0 {
 			continue
 		}