filters: export mime type and filename in env

Export AERC_MIME_TYPE and AERC_FILENAME in the filters command
environment. This allows dynamic coloring with tools that require
a filename and/or a mime type to determine the syntax.

Update docs and add example use in the default config file.

Signed-off-by: Robin Jarry <robin@jarry.cc>
Acked-by: Moritz Poldrack <moritz@poldrack.dev>

CHANGELOG.md

@@ -20,6 +20,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   handler (i.e. `:open gimp` to open attachment in GIMP).
 - Restored XOAUTH2 support for IMAP and SMTP.
 - Support for attaching files with `mailto:`-links
+- Filter commands now have the `AERC_MIME_TYPE` and `AERC_FILENAME` variables
+  defined in their environment.
 
 ### Changed
 

config/aerc.conf

@@ -310,6 +310,11 @@ reply-to-self=true
 #   $PREFIX/share/aerc/filters
 #   /usr/share/aerc/filters
 #
+# The following variables are defined in the filter command environment:
+#
+#   AERC_MIME_TYPE      the part MIME type/subtype
+#   AERC_FILENAME       the attachment filename (if any)
+#
 # The first filter which matches the email's mimetype will be used, so order
 # them from most to least specific.
 #
@@ -323,6 +328,7 @@ message/delivery-status=colorize
 message/rfc822=colorize
 #text/html=pandoc -f html -t plain | colorize
 #text/html=html | colorize
+#text/*=bat -fP --file-name="$AERC_FILENAME"
 #application/x-sh=bat -fP -l sh
 #image/*=catimg -w $(tput cols) -
 #subject,~Git(hub|lab)=lolcat -f

doc/aerc-config.5.scd

@@ -520,6 +520,13 @@ $PREFIX/share/aerc/filters
 /usr/share/aerc/filters
 ```
 
+The following variables are defined in the filter command environment:
+
+_AERC_MIME_TYPE_
+	the part MIME type/subtype
+_AERC_FILENAME_
+	the attachment filename (if any)
+
 Note that said email body is converted into UTF-8 before being passed to
 filters.
 

widgets/msgviewer.go

@@ -541,8 +541,9 @@ func NewPartViewer(acct *AccountView, conf *config.AercConfig,
 	pager = exec.Command(cmd[0], cmd[1:]...)
 
 	info := msg.MessageInfo()
+	mime := part.FullMIMEType()
+
 	for _, f := range conf.Filters {
-		mime := part.FullMIMEType()
 		switch f.FilterType {
 		case config.FILTER_MIMETYPE:
 			if fnmatch.Match(f.Filter, mime, 0) {
@@ -577,6 +578,10 @@ func NewPartViewer(acct *AccountView, conf *config.AercConfig,
 		}
 		filter.Env = os.Environ()
 		filter.Env = append(filter.Env, fmt.Sprintf("PATH=%s", path))
+		filter.Env = append(filter.Env,
+			fmt.Sprintf("AERC_MIME_TYPE=%s", mime))
+		filter.Env = append(filter.Env,
+			fmt.Sprintf("AERC_FILENAME=%s", part.FileName()))
 		if pipe, err = filter.StdinPipe(); err != nil {
 			return nil, err
 		}