m4: want_zstd.m4 - Simplify pkg-config check

This commit simplifies the package check to be more consistent with the
other pkg-config module checks, which lowers the burden of maintenance.

diff --git a/m4/want_zstd.m4 b/m4/want_zstd.m4
index 57b1b03477880b7adb3aa2dc9a79f948f9aeb680..ce70f213ea8e2f98c73ccdc319e8b9a810f96ae3 100644 (file)
--- a/m4/want_zstd.m4
+++ b/m4/want_zstd.m4
@@ -1,21 +1,27 @@
 AC_DEFUN([DOVECOT_WANT_ZSTD], [
   have_zstd=no
 
-  AS_IF([test $want_zstd = yes], [
-    PKG_CHECK_MODULES([ZSTD], [libzstd], [have_zstd=yes], [AC_MSG_ERROR([libzstd not found])])
-  ], [AS_IF([test $want_zstd != no], [
-      PKG_CHECK_MODULES([ZSTD], [libzstd], [have_zstd=yes], [have_zstd=no])
+  AS_IF([test "$want_zstd" != "no"], [
+    PKG_CHECK_MODULES([ZSTD], [libzstd], [have_zstd=yes], [
+      have_zstd=no
+
+      AS_IF([test "$want_zstd" = "yes"], [
+        AC_MSG_ERROR([cannot build with zstd support: zstd library (libzstd) not found])
+      ])
     ])
   ])
 
-  AS_IF([test $have_zstd = yes], [
+  AS_IF([test "$have_zstd" != "no"], [
     have_compress_lib=yes
     COMPRESS_LIBS="$COMPRESS_LIBS $ZSTD_LIBS"
-    AC_DEFINE([HAVE_ZSTD], [], [Define if you have ZSTD library])
-    AC_CHECK_DECLS([ZSTD_error_parameter_unsupported, ZSTD_minCLevel], [], [], [[#include <zstd_errors.h>]])
-    AC_CHECK_LIB([zstd], [ZSTD_getErrorCode], [
-       AC_DEFINE([HAVE_ZSTD_GETERRORCODE], [1], [Whether zstd has ZSTD_getErrorCode])
-    ], [])
+    AC_DEFINE(HAVE_ZSTD,, [Define if you have ZSTD library])
+
+    AC_CHECK_DECLS([ZSTD_error_parameter_unsupported, ZSTD_minCLevel], [], [], [[
+      #include <zstd_errors.h>
+    ]])
+    AC_CHECK_LIB(zstd, ZSTD_getErrorCode, [
+      AC_DEFINE(HAVE_ZSTD_GETERRORCODE, [1], [Whether zstd has ZSTD_getErrorCode])
+    ])
   ])
 
   AM_CONDITIONAL([BUILD_ZSTD], test "$have_zstd" = "yes")