Add a Swift package registry client

README.md

@@ -134,6 +134,7 @@ packages = registries.BulkFetchPackagesWithConcurrency(ctx, purls, nil, 5)
 | Maven | `pkg:maven/org.apache.commons/commons-lang3@3.12.0` |
 | RubyGems | `pkg:gem/rails@7.1.0` |
 | Terraform | `pkg:terraform/hashicorp/consul/aws@0.11.0` |
+| Swift | `pkg:swift/apple/swift-nio@2.65.0?repository_url=https://packages.example.com` |
 
 ## Direct Registry Usage
 
@@ -192,6 +193,9 @@ import _ "github.com/git-pkgs/registries/all"
 | Homebrew | `brew` | https://formulae.brew.sh |
 | Deno | `deno` | https://apiland.deno.dev |
 | Terraform | `terraform` | https://registry.terraform.io |
+| Swift | `swift` | URL required |
+
+Swift package names are a registry scope and name, written `scope/name` (the PURL namespace and name) or `scope.name`. A host-style PURL namespace such as `pkg:swift/github.com/apple/swift-argument-parser` has no defined mapping to a registry scope, so the Swift client rejects it.
 
 ## Types
 

all/all.go

@@ -38,5 +38,6 @@ import (
 	_ "github.com/git-pkgs/registries/internal/pub"
 	_ "github.com/git-pkgs/registries/internal/pypi"
 	_ "github.com/git-pkgs/registries/internal/rubygems"
+	_ "github.com/git-pkgs/registries/internal/swift"
 	_ "github.com/git-pkgs/registries/internal/terraform"
 )

client/client.go

@@ -61,8 +61,24 @@ func (c *Client) GetJSON(ctx context.Context, url string, v any) error {
 	return json.Unmarshal(body, v)
 }
 
+// GetJSONWithHeaders fetches a URL with extra request headers, which replace
+// the defaults of the same name, decodes the JSON response into v and returns
+// the response headers.
+func (c *Client) GetJSONWithHeaders(ctx context.Context, url string, header http.Header, v any) (http.Header, error) {
+	body, respHeader, err := c.getBody(ctx, url, header)
+	if err != nil {
+		return nil, err
+	}
+	return respHeader, json.Unmarshal(body, v)
+}
+
 // GetBody fetches a URL and returns the response body.
 func (c *Client) GetBody(ctx context.Context, url string) ([]byte, error) {
+	body, _, err := c.getBody(ctx, url, nil)
+	return body, err
+}
+
+func (c *Client) getBody(ctx context.Context, url string, header http.Header) ([]byte, http.Header, error) {
 	var lastErr error
 
 	for attempt := 0; attempt <= c.MaxRetries; attempt++ {
@@ -73,64 +89,67 @@ func (c *Client) GetBody(ctx context.Context, url string) ([]byte, error) {
 
 			select {
 			case <-ctx.Done():
-				return nil, ctx.Err()
+				return nil, nil, ctx.Err()
 			case <-time.After(delay):
 			}
 		}
 
 		if c.RateLimiter != nil {
 			if err := c.RateLimiter.Wait(ctx); err != nil {
-				return nil, err
+				return nil, nil, err
 			}
 		}
 
-		body, err := c.doRequest(ctx, url)
+		body, respHeader, err := c.doRequest(ctx, url, header)
 		if err == nil {
-			return body, nil
+			return body, respHeader, nil
 		}
 
 		lastErr = err
 		if errors.Is(err, ErrUpstreamHeld) {
-			return nil, err
+			return nil, nil, err
 		}
 		var rateErr *RateLimitError
 		if errors.As(err, &rateErr) {
-			return nil, err
+			return nil, nil, err
 		}
 
 		var httpErr *HTTPError
 		if ok := isHTTPError(err, &httpErr); ok {
 			if httpErr.StatusCode == http.StatusNotFound {
-				return nil, err
+				return nil, nil, err
 			}
 			if httpErr.StatusCode == http.StatusTooManyRequests || httpErr.StatusCode >= http.StatusInternalServerError {
 				continue
 			}
-			return nil, err
+			return nil, nil, err
 		}
 	}
 
-	return nil, lastErr
+	return nil, nil, lastErr
 }
 
-func (c *Client) doRequest(ctx context.Context, url string) ([]byte, error) {
+func (c *Client) doRequest(ctx context.Context, url string, header http.Header) ([]byte, http.Header, error) {
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
 	req.Header.Set("User-Agent", c.UserAgent)
 	req.Header.Set("Accept", "application/json")
+	for name, values := range header {
+		req.Header[http.CanonicalHeaderKey(name)] = values
+	}
 
 	resp, err := c.HTTPClient.Do(req)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	defer func() { _ = resp.Body.Close() }()
 
 	body, err := io.ReadAll(io.LimitReader(resp.Body, maxResponseSize))
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
 	if resp.StatusCode >= http.StatusBadRequest {
@@ -145,13 +164,13 @@ func (c *Client) doRequest(ctx context.Context, url string) ([]byte, error) {
 				if delay%time.Second != 0 {
 					seconds++
 				}
-				return nil, &RateLimitError{RetryAfter: int(seconds)}
+				return nil, nil, &RateLimitError{RetryAfter: int(seconds)}
 			}
 		}
-		return nil, httpErr
+		return nil, nil, httpErr
 	}
 
-	return body, nil
+	return body, resp.Header, nil
 }
 
 func isHTTPError(err error, target **HTTPError) bool {

client/client_test.go

@@ -115,3 +115,34 @@ func TestResponseWithinLimit(t *testing.T) {
 		t.Fatalf("got %q, want %q", string(body), payload)
 	}
 }
+
+func TestGetJSONWithHeaders(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if got := r.Header.Values("Accept"); len(got) != 1 || got[0] != "application/vnd.example+json" {
+			t.Errorf("Accept = %v, want only the supplied value", got)
+		}
+		if r.Header.Get("User-Agent") == "" {
+			t.Error("default User-Agent was dropped")
+		}
+		w.Header().Set("Link", `<https://example.com/?page=2>; rel="next"`)
+		_, _ = w.Write([]byte(`{"name":"test"}`))
+	}))
+	defer srv.Close()
+
+	c := DefaultClient()
+	c.MaxRetries = 0
+
+	var result struct {
+		Name string `json:"name"`
+	}
+	header, err := c.GetJSONWithHeaders(context.Background(), srv.URL, http.Header{"accept": {"application/vnd.example+json"}}, &result)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result.Name != "test" {
+		t.Errorf("got %+v", result)
+	}
+	if header.Get("Link") == "" {
+		t.Error("response headers not returned")
+	}
+}

fetch/swift_resolver_test.go

@@ -0,0 +1,28 @@
+package fetch
+
+import (
+	"context"
+	"testing"
+
+	"github.com/git-pkgs/registries"
+	_ "github.com/git-pkgs/registries/internal/swift"
+)
+
+func TestResolveSwift(t *testing.T) {
+	reg, err := registries.New("swift", "https://packages.example.com", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	r := NewResolver()
+	r.RegisterRegistry(reg)
+
+	for _, name := range []string{"apple/swift-nio", "apple.swift-nio"} {
+		info, err := r.Resolve(context.Background(), "swift", name, "2.65.0")
+		if err != nil {
+			t.Fatalf("Resolve(%q) failed: %v", name, err)
+		}
+		if want := "https://packages.example.com/apple/swift-nio/2.65.0.zip"; info.URL != want {
+			t.Errorf("URL = %q, want %q", info.URL, want)
+		}
+	}
+}