From fd8f55ffd25bfe4eed1524f3daba2f05f8dd373e Mon Sep 17 00:00:00 2001
From: Sergey Poznyakoff <gray@gnu.org>
Date: Tue, 18 Jun 2019 00:06:40 +0300
Subject: Don't accept database types not supported by mailutils

For details, see the last paragraph in:

http://mail.gnu.org.ua/mailman/listarchive/bug-mailfromd/2019-06/msg00001.html

* configure.ac (db_type_to_feature): Make sure empty string is never
returned.
---
 configure.ac | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 54c9ebd8..289a2916 100644
--- a/configure.ac
+++ b/configure.ac
@@ -146,8 +146,21 @@ ndbm:ndbm
 
 # Convert database type to mailutils feature
 db_type_to_feature() {
-    sed -n /^$(echo "$1" | tr A-Z a-z)':/s/.*://p' <<EOF
+    # Normalize the input
+    key=$(echo "$1" | tr A-Z a-z)
+    # Augment db_map with the line "$key:$key" and select from the resulting
+    # input the first entry starting with "$key:". On output, replace it with
+    # the characters that follow : up to the newline.
+    # The first expression looks for the string in the first line of input.
+    # If found, it replaces it and branches to the end of script. The second
+    # expression then has no chance to catch, since the scanning resumes from
+    # line 2. Otherwise, if key is not found in the first line, the second
+    # expression searches for it in the remaining lines.
+    # The default entry "$key:$key" ensures the normalized key is returned
+    # if no match was found.
+    sed -n -e "1s/^$key"'://p;t' -e '1,//{s///p}' <<EOF
 $db_map
+$key:$key
 EOF
 }
 
@@ -201,6 +214,9 @@ else
   feature=$(mailutils info $fl | head -n 1 | sed 's/WITH_//')
   if test -n "$feature"; then
       DEFAULT_DB_TYPE=$(db_feature_to_type $feature)
+      if test -z "$DEFAULT_DB_TYPE"; then
+        AC_MSG_WARN([can't select database type $feature, falling back to default])
+      fi
   fi
 fi
 if test -n "$DEFAULT_DB_TYPE"; then
-- 
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