[PATCH] Display extra headers for emacs-mua - db config option

[Johan Parin]

Modify format_headers_sprinter so that it returns some additional headers in the
sexp, instead of a small fixed set of headers.

The extra header list is configured by the database config option
`show.extra_headers'.

This is required in order for the elisp variable
`notmuch-message-headers' to work.

See this bug report:

  https://notmuchmail.org/pipermail/notmuch/2017/026069.html
---
 doc/man1/notmuch-config.rst |  6 ++++++
 notmuch-config.c            |  7 ++++---
 notmuch-show.c              | 41 ++++++++++++++++++++++++++++++++++++-
 3 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/doc/man1/notmuch-config.rst b/doc/man1/notmuch-config.rst
index 28487079..0eb59883 100644
--- a/doc/man1/notmuch-config.rst
+++ b/doc/man1/notmuch-config.rst
@@ -204,6 +204,12 @@ The available configuration items are described below.
     supported. See **notmuch-search-terms(7)** for a list of existing
     prefixes, and an explanation of probabilistic prefixes.
 
+**show.extra_headers**
+    A list of extra headers that will be output by **notmuch show**
+    with ``--format=sexp``, if present in the message.
+
+    Default: empty list.
+
 **built_with.<name>**
     Compile time feature <name>. Current possibilities include
     "compact" (see **notmuch-compact(1)**) and "field_processor" (see
diff --git a/notmuch-config.c b/notmuch-config.c
index 1b079e85..6554ad9b 100644
--- a/notmuch-config.c
+++ b/notmuch-config.c
@@ -841,9 +841,10 @@ typedef struct config_key {
 
 static struct config_key
     config_key_table[] = {
-    { "index.decrypt",   true,   false,  NULL },
-    { "index.header.",   true,   true,   validate_field_name },
-    { "query.",          true,   true,   NULL },
+    { "index.decrypt",      true,   false,  NULL },
+    { "index.header.",      true,   true,   validate_field_name },
+    { "query.",             true,   true,   NULL },
+    { "show.extra_headers", true,   false,  NULL }
 };
 
 static config_key_info_t *
diff --git a/notmuch-show.c b/notmuch-show.c
index 21792a57..4c77468f 100644
--- a/notmuch-show.c
+++ b/notmuch-show.c
@@ -18,11 +18,16 @@
  * Author: Carl Worth <cworth at cworth.org>
  */
 
+#include <string.h>
+
 #include "notmuch-client.h"
 #include "gmime-filter-reply.h"
 #include "sprinter.h"
 #include "zlib-extra.h"
 
+static notmuch_database_t *notmuch = NULL;
+
+
 static const char *
 _get_tags_as_string (const void *ctx, notmuch_message_t *message)
 {
@@ -195,6 +200,38 @@ _is_from_line (const char *line)
 	return 0;
 }
 
+/* Output extra headers if configured with the `show.extra_headers'
+ * database configuration option
+ */
+void
+format_extra_headers_sprinter (sprinter_t *sp, GMimeMessage *message)
+{
+    GMimeHeaderList *header_list;
+    GMimeHeader *header;
+    char *extra_headers, *tofree, *header_name;
+
+    if (notmuch == NULL)
+	return;
+
+    if (notmuch_database_get_config (notmuch, "show.extra_headers",
+				     &extra_headers) != NOTMUCH_STATUS_SUCCESS)
+	return;
+
+    header_list  = g_mime_object_get_header_list (GMIME_OBJECT(message));
+
+    tofree = extra_headers;
+    while ( (header_name = strsep(&extra_headers, ";")) != NULL) {
+
+	header = g_mime_header_list_get_header (header_list, header_name);
+	if (header == NULL)
+	    continue;
+
+	sp->map_key (sp, g_mime_header_get_name(header));
+	sp->string (sp, g_mime_header_get_value(header));
+    }
+    free (tofree);
+}
+
 void
 format_headers_sprinter (sprinter_t *sp, GMimeMessage *message,
 			 bool reply, const _notmuch_message_crypto_t *msg_crypto)
@@ -253,6 +290,9 @@ format_headers_sprinter (sprinter_t *sp, GMimeMessage *message,
     } else {
 	sp->map_key (sp, "Date");
 	sp->string (sp, g_mime_message_get_date_string (sp, message));
+
+	/* Output extra headers the user has configured in the database, if any */
+	format_extra_headers_sprinter (sp, message);
     }
 
     sp->end (sp);
@@ -1152,7 +1192,6 @@ static const notmuch_show_format_t *formatters[] = {
 int
 notmuch_show_command (notmuch_config_t *config, int argc, char *argv[])
 {
-    notmuch_database_t *notmuch;
     notmuch_query_t *query;
     char *query_string;
     int opt_index, ret;
-- 
2.21.0 (Apple Git-122)