[azcore] Adding in a function create a policy.Request using an existi…

…ng *http.Request (#23186)

Adding in a function create a policy.Request using an already created http.Request. This is useful if you want to use our pipelines in contexts where we're not in our generated clients.

sdk/azcore/CHANGELOG.md

@@ -4,6 +4,8 @@
 
 ### Features Added
 
+- Added runtime.NewRequestFromRequest(), allowing for a policy.Request to be created from an existing *http.Request.
+
 ### Breaking Changes
 
 ### Bugs Fixed

sdk/azcore/internal/exported/exported_test.go

@@ -7,7 +7,10 @@
 package exported
 
 import (
+	"bytes"
+	"context"
 	"fmt"
+	"io"
 	"net/http"
 	"strings"
 	"testing"
@@ -74,3 +77,72 @@ func TestNewSASCredential(t *testing.T) {
 	cred.Update(val2)
 	require.EqualValues(t, val2, SASCredentialGet(cred))
 }
+
+func TestNewRequestFromRequest(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	expectedData := bytes.NewReader([]byte{1, 2, 3, 4, 5})
+
+	httpRequest, err := http.NewRequestWithContext(ctx, "POST", "https://example.com", expectedData)
+	require.NoError(t, err)
+
+	req, err := NewRequestFromRequest(httpRequest)
+	require.NoError(t, err)
+
+	// our stream has been drained - the func has to make a copy of the body so it can be seekable.
+	// so our stream should be at end.
+	currentPos, err := expectedData.Seek(0, io.SeekCurrent)
+	require.NoError(t, err)
+	require.Equal(t, int64(5), currentPos)
+
+	actualData, err := io.ReadAll(req.Body())
+	require.NoError(t, err)
+	require.Equal(t, []byte{1, 2, 3, 4, 5}, actualData)
+
+	// now we change stuff in the policy.Request...
+	replacementBuff := bytes.NewReader([]byte{6})
+	err = req.SetBody(NopCloser(replacementBuff), "application/coolstuff")
+	require.NoError(t, err)
+
+	// and it's automatically reflected in the http.Request, which helps us with interop
+	// with other HTTP pipelines.
+	require.Equal(t, "application/coolstuff", httpRequest.Header.Get("Content-Type"))
+	newBytes, err := io.ReadAll(httpRequest.Body)
+	require.NoError(t, err)
+	require.Equal(t, []byte{6}, newBytes)
+}
+
+func TestNewRequestFromRequest_AvoidExtraCopyIfReadSeekCloser(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	expectedData := NopCloser(bytes.NewReader([]byte{1, 2, 3, 4, 5}))
+
+	httpRequest, err := http.NewRequestWithContext(ctx, "POST", "https://example.com", expectedData)
+	require.NoError(t, err)
+
+	req, err := NewRequestFromRequest(httpRequest)
+	require.NoError(t, err)
+
+	// our stream should _NOT_ get drained since it was already an io.ReadSeekCloser
+	currentPos, err := expectedData.Seek(0, io.SeekCurrent)
+	require.NoError(t, err)
+	require.Equal(t, int64(0), currentPos)
+
+	actualData, err := io.ReadAll(req.Body())
+	require.NoError(t, err)
+	require.Equal(t, []byte{1, 2, 3, 4, 5}, actualData)
+
+	// now we change stuff in the policy.Request...
+	replacementBuff := bytes.NewReader([]byte{6})
+	err = req.SetBody(NopCloser(replacementBuff), "application/coolstuff")
+	require.NoError(t, err)
+
+	// and it's automatically reflected in the http.Request, which helps us with interop
+	// with other HTTP pipelines.
+	require.Equal(t, "application/coolstuff", httpRequest.Header.Get("Content-Type"))
+	newBytes, err := io.ReadAll(httpRequest.Body)
+	require.NoError(t, err)
+	require.Equal(t, []byte{6}, newBytes)
+}

sdk/azcore/internal/exported/request.go

@@ -7,6 +7,7 @@
 package exported
 
 import (
+	"bytes"
 	"context"
 	"encoding/base64"
 	"errors"
@@ -67,6 +68,42 @@ func (ov opValues) get(value any) bool {
 	return ok
 }
 
+// NewRequestFromRequest creates a new policy.Request with an existing *http.Request
+// Exported as runtime.NewRequestFromRequest().
+func NewRequestFromRequest(req *http.Request) (*Request, error) {
+	policyReq := &Request{req: req}
+
+	if req.Body != nil {
+		// we can avoid a body copy here if the underlying stream is already a
+		// ReadSeekCloser.
+		readSeekCloser, isReadSeekCloser := req.Body.(io.ReadSeekCloser)
+
+		if !isReadSeekCloser {
+			// since this is an already populated http.Request we want to copy
+			// over its body, if it has one.
+			bodyBytes, err := io.ReadAll(req.Body)
+
+			if err != nil {
+				return nil, err
+			}
+
+			if err := req.Body.Close(); err != nil {
+				return nil, err
+			}
+
+			readSeekCloser = NopCloser(bytes.NewReader(bodyBytes))
+		}
+
+		// SetBody also takes care of updating the http.Request's body
+		// as well, so they should stay in-sync from this point.
+		if err := policyReq.SetBody(readSeekCloser, req.Header.Get("Content-Type")); err != nil {
+			return nil, err
+		}
+	}
+
+	return policyReq, nil
+}
+
 // NewRequest creates a new Request with the specified input.
 // Exported as runtime.NewRequest().
 func NewRequest(ctx context.Context, httpMethod string, endpoint string) (*Request, error) {

sdk/azcore/runtime/request.go

@@ -15,6 +15,7 @@ import (
 	"fmt"
 	"io"
 	"mime/multipart"
+	"net/http"
 	"net/textproto"
 	"net/url"
 	"path"
@@ -45,6 +46,11 @@ func NewRequest(ctx context.Context, httpMethod string, endpoint string) (*polic
 	return exported.NewRequest(ctx, httpMethod, endpoint)
 }
 
+// NewRequestFromRequest creates a new policy.Request with an existing *http.Request
+func NewRequestFromRequest(req *http.Request) (*policy.Request, error) {
+	return exported.NewRequestFromRequest(req)
+}
+
 // EncodeQueryParams will parse and encode any query parameters in the specified URL.
 // Any semicolons will automatically be escaped.
 func EncodeQueryParams(u string) (string, error) {