client: add utilities to encode platforms

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

client/image_history.go

@@ -17,11 +17,11 @@ func (cli *Client) ImageHistory(ctx context.Context, imageID string, opts image.
 			return nil, err
 		}
 
-		p, err := json.Marshal(*opts.Platform)
+		p, err := encodePlatform(opts.Platform)
 		if err != nil {
 			return nil, fmt.Errorf("invalid platform: %v", err)
 		}
-		query.Set("platform", string(p))
+		query.Set("platform", p)
 	}
 
 	var history []image.HistoryResponseItem

client/image_load.go

@@ -2,7 +2,6 @@ package client // import "github.com/docker/docker/client"
 
 import (
 	"context"
-	"encoding/json"
 	"io"
 	"net/http"
 	"net/url"
@@ -28,11 +27,11 @@ func (cli *Client) ImageLoad(ctx context.Context, input io.Reader, opts image.Lo
 			return image.LoadResponse{}, err
 		}
 
-		p, err := json.Marshal(*opts.Platform)
+		p, err := encodePlatform(opts.Platform)
 		if err != nil {
 			return image.LoadResponse{}, err
 		}
-		query.Set("platform", string(p))
+		query.Set("platform", p)
 	}
 
 	resp, err := cli.postRaw(ctx, "/images/load", query, input, http.Header{

client/image_save.go

@@ -2,8 +2,6 @@ package client // import "github.com/docker/docker/client"
 
 import (
 	"context"
-	"encoding/json"
-	"fmt"
 	"io"
 	"net/url"
 
@@ -22,11 +20,11 @@ func (cli *Client) ImageSave(ctx context.Context, imageIDs []string, opts image.
 			return nil, err
 		}
 
-		p, err := json.Marshal(*opts.Platform)
+		p, err := encodePlatform(opts.Platform)
 		if err != nil {
-			return nil, fmt.Errorf("invalid platform: %v", err)
+			return nil, err
 		}
-		query.Set("platform", string(p))
+		query.Set("platform", p)
 	}
 
 	resp, err := cli.get(ctx, "/images/get", query, nil)

client/utils.go

@@ -1,10 +1,14 @@
 package client // import "github.com/docker/docker/client"
 
 import (
+	"encoding/json"
+	"fmt"
 	"net/url"
 	"regexp"
 
 	"github.com/docker/docker/api/types/filters"
+	"github.com/docker/docker/errdefs"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
 var headerRegexp = regexp.MustCompile(`\ADocker/.+\s\((.+)\)\z`)
@@ -32,3 +36,43 @@ func getFiltersQuery(f filters.Args) (url.Values, error) {
 	}
 	return query, nil
 }
+
+// encodePlatforms marshals the given platform(s) to JSON format, to
+// be used for query-parameters for filtering / selecting platforms.
+func encodePlatforms(platform ...ocispec.Platform) ([]string, error) {
+	if len(platform) == 0 {
+		return []string{}, nil
+	}
+	if len(platform) == 1 {
+		p, err := encodePlatform(&platform[0])
+		if err != nil {
+			return nil, err
+		}
+		return []string{p}, nil
+	}
+
+	seen := make(map[string]struct{}, len(platform))
+	out := make([]string, 0, len(platform))
+	for i := range platform {
+		p, err := encodePlatform(&platform[i])
+		if err != nil {
+			return nil, err
+		}
+		if _, ok := seen[p]; !ok {
+			out = append(out, p)
+			seen[p] = struct{}{}
+		}
+	}
+	return out, nil
+}
+
+// encodePlatforms marshals the given platform to JSON format, to
+// be used for query-parameters for filtering / selecting platforms. It
+// is used as a helper for encodePlatforms,
+func encodePlatform(platform *ocispec.Platform) (string, error) {
+	p, err := json.Marshal(platform)
+	if err != nil {
+		return "", errdefs.InvalidParameter(fmt.Errorf("invalid platform: %v", err))
+	}
+	return string(p), nil
+}

client/utils_test.go

@@ -0,0 +1,56 @@
+package client
+
+import (
+	"testing"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"gotest.tools/v3/assert"
+)
+
+func TestEncodePlatforms(t *testing.T) {
+	tests := []struct {
+		doc       string
+		platforms []ocispec.Platform
+		expected  []string
+	}{
+		{
+			doc: "single platform",
+			platforms: []ocispec.Platform{
+				{Architecture: "arm64", OS: "windows", Variant: "v8", OSVersion: "99.99.99"},
+			},
+			expected: []string{
+				`{"architecture":"arm64","os":"windows","os.version":"99.99.99","variant":"v8"}`,
+			},
+		},
+		{
+			doc: "multiple platforms",
+			platforms: []ocispec.Platform{
+				{Architecture: "arm64", OS: "linux", Variant: "v8"},
+				{Architecture: "arm64", OS: "windows", Variant: "v8", OSVersion: "99.99.99"},
+			},
+			expected: []string{
+				`{"architecture":"arm64","os":"linux","variant":"v8"}`,
+				`{"architecture":"arm64","os":"windows","os.version":"99.99.99","variant":"v8"}`,
+			},
+		},
+		{
+			doc: "multiple platforms with duplicates",
+			platforms: []ocispec.Platform{
+				{Architecture: "arm64", OS: "linux", Variant: "v8"},
+				{Architecture: "arm64", OS: "windows", Variant: "v8", OSVersion: "99.99.99"},
+				{Architecture: "arm64", OS: "linux", Variant: "v8"},
+			},
+			expected: []string{
+				`{"architecture":"arm64","os":"linux","variant":"v8"}`,
+				`{"architecture":"arm64","os":"windows","os.version":"99.99.99","variant":"v8"}`,
+			},
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.doc, func(t *testing.T) {
+			out, err := encodePlatforms(tc.platforms...)
+			assert.NilError(t, err)
+			assert.DeepEqual(t, out, tc.expected)
+		})
+	}
+}