feat(v2): add BuildHeaders and InsertMetadataIntoOutgoingContext to h…

…eader (#290)

refs: googleapis/gapic-generator-go#1300
refs: googleapis/gapic-generator-go#1301

v2/header.go

@@ -31,9 +31,15 @@ package gax
 
 import (
  "bytes"
+ "context"
+ "fmt"
+ "net/http"
  "runtime"
  "strings"
  "unicode"
+
+ "github.com/googleapis/gax-go/v2/callctx"
+ "google.golang.org/grpc/metadata"
 )
 
 var (
@@ -117,3 +123,46 @@ func XGoogHeader(keyval ...string) string {
  }
  return buf.String()[1:]
 }
+
+// InsertMetadataIntoOutgoingContext is for use by the Google Cloud Libraries
+// only.
+//
+// InsertMetadataIntoOutgoingContext returns a new context that merges the
+// provided keyvals metadata pairs with any existing metadata/headers in the
+// provided context. keyvals should have a corresponding value for every key
+// provided. If there is an odd number of keyvals this method will panic.
+// Existing values for keys will not be overwritten, instead provided values
+// will be appended to the list of existing values.
+func InsertMetadataIntoOutgoingContext(ctx context.Context, keyvals ...string) context.Context {
+ return metadata.NewOutgoingContext(ctx, insertMetadata(ctx, keyvals...))
+}
+
+// BuildHeaders is for use by the Google Cloud Libraries only.
+//
+// BuildHeaders returns a new http.Header that merges the provided
+// keyvals header pairs with any existing metadata/headers in the provided
+// context. keyvals should have a corresponding value for every key provided.
+// If there is an odd number of keyvals this method will panic.
+// Existing values for keys will not be overwritten, instead provided values
+// will be appended to the list of existing values.
+func BuildHeaders(ctx context.Context, keyvals ...string) http.Header {
+ return http.Header(insertMetadata(ctx, keyvals...))
+}
+
+func insertMetadata(ctx context.Context, keyvals ...string) metadata.MD {
+ if len(keyvals)%2 != 0 {
+ panic(fmt.Sprintf("gax: an even number of key value pairs must be provided, got %d", len(keyvals)))
+ }
+ out, ok := metadata.FromOutgoingContext(ctx)
+ if !ok {
+ out = metadata.MD(make(map[string][]string))
+ }
+ headers := callctx.HeadersFromContext(ctx)
+ for k, v := range headers {
+ out[k] = append(out[k], v...)
+ }
+ for i := 0; i < len(keyvals); i = i + 2 {
+ out[keyvals[i]] = append(out[keyvals[i]], keyvals[i+1])
+ }
+ return out
+}

v2/header_test.go

@@ -30,9 +30,13 @@
 package gax
 
 import (
+ "context"
+ "net/http"
  "testing"
 
  "github.com/google/go-cmp/cmp"
+ "github.com/googleapis/gax-go/v2/callctx"
+ "google.golang.org/grpc/metadata"
 )
 
 func TestXGoogHeader(t *testing.T) {
@@ -89,3 +93,64 @@ func TestGoVersion(t *testing.T) {
  }
  }
 }
+
+func TestInsertMetadataIntoOutgoingContext(t *testing.T) {
+ for _, tst := range []struct {
+ // User-provided metadata set in context
+ userMd metadata.MD
+ // User-provided headers set in context
+ userHeaders []string
+ // Client-provided headers passed to func
+ clientHeaders []string
+ want metadata.MD
+ }{
+ {
+ userMd: metadata.Pairs("key_1", "val_1", "key_2", "val_21"),
+ want: metadata.Pairs("key_1", "val_1", "key_2", "val_21"),
+ },
+ {
+ userHeaders: []string{"key_2", "val_22"},
+ want: metadata.Pairs("key_2", "val_22"),
+ },
+ {
+ clientHeaders: []string{"key_2", "val_23", "key_2", "val_24"},
+ want: metadata.Pairs("key_2", "val_23", "key_2", "val_24"),
+ },
+ {
+ userMd: metadata.Pairs("key_1", "val_1", "key_2", "val_21"),
+ userHeaders: []string{"key_2", "val_22"},
+ clientHeaders: []string{"key_2", "val_23", "key_2", "val_24"},
+ want: metadata.Pairs("key_1", "val_1", "key_2", "val_21", "key_2", "val_22", "key_2", "val_23", "key_2", "val_24"),
+ },
+ } {
+ ctx := context.Background()
+ if tst.userMd != nil {
+ ctx = metadata.NewOutgoingContext(ctx, tst.userMd)
+ }
+ ctx = callctx.SetHeaders(ctx, tst.userHeaders...)
+
+ ctx = InsertMetadataIntoOutgoingContext(ctx, tst.clientHeaders...)
+
+ got, _ := metadata.FromOutgoingContext(ctx)
+ if diff := cmp.Diff(tst.want, got); diff != "" {
+ t.Errorf("InsertMetadata(ctx, %q) mismatch (-want +got):\n%s", tst.clientHeaders, diff)
+ }
+ }
+}
+
+func TestBuildHeaders(t *testing.T) {
+ // User-provided metadata set in context
+ existingMd := metadata.Pairs("key_1", "val_1", "key_2", "val_21")
+ ctx := metadata.NewOutgoingContext(context.Background(), existingMd)
+ // User-provided headers set in context
+ ctx = callctx.SetHeaders(ctx, "key_2", "val_22")
+ // Client-provided headers
+ keyvals := []string{"key_2", "val_23", "key_2", "val_24"}
+
+ got := BuildHeaders(ctx, keyvals...)
+
+ want := http.Header{"key_1": []string{"val_1"}, "key_2": []string{"val_21", "val_22", "val_23", "val_24"}}
+ if diff := cmp.Diff(want, got); diff != "" {
+ t.Errorf("InsertMetadata(ctx, %q) mismatch (-want +got):\n%s", keyvals, diff)
+ }
+}