Provide an error message on bogus config file spec

If local.conf specifies a config file addition in the following way...

[[post-config|$MY_CONF_FILE]]
[xyz]
foo=bar

...and $MY_CONF_FILE points to a file whose directory is not writable by
the user running the script, then stack.sh aborts with the following
obscure message:

  2015-09-01 08:20:08.113 | touch: setting times of '/': Permission denied

This patch modifies inc/meta-config to provide a useful error message,
such as:

  2015-09-01 08:20:08.114 | could not create config file / ($MY_CONF_FILE)

This patch also modifies inc/meta-config so that it provides an error
message if $MY_CONF_FILE is empty (instead of silently ignoring this local.conf
statement):

  2015-09-01 09:38:53.406 | bogus config file specification: $MY_CONF_FILE
  is undefined

Change-Id: I9b78407420318548561012a8672762bc7fdd6db6
Closes-Bug: 1490881

Author: tmmorin

inc/meta-config

@@ -89,9 +89,10 @@ function merge_config_file {
     # note, configfile might be a variable (note the iniset, etc
     # created in the mega-awk below is "eval"ed too, so we just leave
     # it alone.
-    local real_configfile=$(eval echo $configfile)
+    local real_configfile
+    real_configfile=$(eval echo $configfile)
     if [ ! -f $real_configfile ]; then
-        touch $real_configfile
+        touch $real_configfile || die $LINENO "could not create config file $real_configfile ($configfile)"
     fi
 
     get_meta_section $file $matchgroup $configfile | \
@@ -177,8 +178,18 @@ function merge_config_group {
     local configfile group
     for group in $matchgroups; do
         for configfile in $(get_meta_section_files $localfile $group); do
-            if [[ -d $(dirname $(eval "echo $configfile")) ]]; then
+            local realconfigfile
+            local dir
+
+            realconfigfile=$(eval "echo $configfile")
+            if [[ -z $realconfigfile ]]; then
+                die $LINENO "bogus config file specification: $configfile is undefined"
+            fi
+            dir=$(dirname $realconfigfile)
+            if [[ -d $dir ]]; then
                 merge_config_file $localfile $group $configfile
+            else
+                die $LINENO "bogus config file specification $configfile ($configfile=$realconfigfile, $dir is not a directory)"
             fi
         done
     done

tests/test_meta_config.sh

@@ -23,6 +23,12 @@ function check_result {
     fi
 }
 
+# mock function-common:die so that it does not
+# interupt our test script
+function die {
+    exit -1
+}
+
 TEST_1C_ADD="[eee]
 type=new
 multi = foo2"
@@ -110,6 +116,15 @@ attr = strip_trailing_space
 [DEFAULT]
 servers=10.11.12.13:80
 
+[[test8|/permission-denied.conf]]
+foo=bar
+
+[[test9|\$UNDEF]]
+foo=bar
+
+[[test10|does-not-exist-dir/test.conf]]
+foo=bar
+
 [[test-multi-sections|test-multi-sections.conf]]
 [sec-1]
 cfg_item1 = abcd
@@ -340,6 +355,36 @@ EXPECT_VAL="
 servers = 10.11.12.13:80"
 check_result "$VAL" "$EXPECT_VAL"
 
+echo "merge_config_file test8 non-touchable conf file: "
+set +e
+# function is expected to fail and exit, running it
+# in a subprocess to let this script proceed
+(merge_config_file test.conf test8 /permission-denied.conf)
+VAL=$?
+EXPECT_VAL=255
+check_result "$VAL" "$EXPECT_VAL"
+set -e
+
+echo -n "merge_config_group test9 undefined conf file: "
+set +e
+# function is expected to fail and exit, running it
+# in a subprocess to let this script proceed
+(merge_config_group test.conf test9)
+VAL=$?
+EXPECT_VAL=255
+check_result "$VAL" "$EXPECT_VAL"
+set -e
+
+echo -n "merge_config_group test10 not directory: "
+set +e
+# function is expected to fail and exit, running it
+# in a subprocess to let this script proceed
+(merge_config_group test.conf test10)
+VAL=$?
+EXPECT_VAL=255
+check_result "$VAL" "$EXPECT_VAL"
+set -e
+
 rm -f test.conf test1c.conf test2a.conf \
     test-space.conf test-equals.conf test-strip.conf \
     test-colon.conf test-env.conf test-multiline.conf \