compose: explicitly identify converted text/* parts

When running :accept, an error is displayed on the review screen:

 text/calendar error: no command defined for mime/type

When running :multipart text/xxx, its contents are not specified. They
are regenerated every time the review screen is displayed. When running
:accept, a text/calendar part is added with actual contents.

Update the Part object to hold a boolean initialized when first being
created. If body is nil, identify the part as "Converted" and update its
contents every time the review screen is displayed. When body is not nil
but contains text (e.g. when running :accept), identify the part as
*not* converted and ignore the conversion step.

Fixes: cbcabfafaab2 ("compose: allow writing multipart/alternative messages")
Reported-by: Inwit <inwit@sindominio.net>
Signed-off-by: Robin Jarry <robin@jarry.cc>
Tested-by: Inwit <inwit@sindominio.net>

3 files changed, 20 insertions, 9 deletions

diff --git a/app/compose.go b/app/compose.go
index 22d862aa..9f9ebf39 100644
--- a/app/compose.go
+++ b/app/compose.go
@@ -1787,7 +1787,10 @@ func (c *Composer) updateMultipart(p *lib.Part) error {
 		p.ConversionError = e
 		return e
 	}
-
+	if !p.Converted {
+		// text/* multipart created without a command (e.g. by :accept)
+		return nil
+	}
 	command, found := config.Converters[p.MimeType]
 	if !found {
 		// unreachable
diff --git a/commands/compose/multipart.go b/commands/compose/multipart.go
index 13fe8ca3..a38e0a6e 100644
--- a/commands/compose/multipart.go
+++ b/commands/compose/multipart.go
@@ -1,7 +1,6 @@
 package compose
 
 import (
-	"bytes"
 	"fmt"
 
 	"git.sr.ht/~rjarry/aerc/app"
@@ -52,7 +51,7 @@ func (m Multipart) Execute(args []string) error {
 			map[string]string{"Charset": "UTF-8"},
 			// the actual content of the part will be rendered
 			// every time the body of the email is updated
-			bytes.NewReader([]byte{}),
+			nil,
 		)
 		if err != nil {
 			return err
diff --git a/lib/attachment.go b/lib/attachment.go
index 6f29da55..a5f1b034 100644
--- a/lib/attachment.go
+++ b/lib/attachment.go
@@ -19,19 +19,28 @@ type Part struct {
 	MimeType        string
 	Params          map[string]string
 	Data            []byte
+	Converted       bool
 	ConversionError error
 }
 
 func NewPart(mimetype string, params map[string]string, body io.Reader,
 ) (*Part, error) {
-	d, err := io.ReadAll(body)
-	if err != nil {
-		return nil, err
+	var d []byte
+	var err error
+	var converted bool
+	if body == nil {
+		converted = true
+	} else {
+		d, err = io.ReadAll(body)
+		if err != nil {
+			return nil, err
+		}
 	}
 	return &Part{
-		MimeType: mimetype,
-		Params:   params,
-		Data:     d,
+		MimeType:  mimetype,
+		Params:    params,
+		Data:      d,
+		Converted: converted,
 	}, nil
 }