test-lib: silence "-x" cleanup under bash

diff --git a/t/test-lib.sh b/t/test-lib.sh
index 9b61f16f7a8807ad96014d79f1d1b968397584bf..7914453a3b382d9f7d76b5fb55c532d458138d9c 100644 (file)
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -175,9 +175,10 @@ esac
 
 # Convenience
 #
-# A regexp to match 5 and 40 hexdigits
+# A regexp to match 5, 35 and 40 hexdigits
 _x05='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
-_x40="$_x05$_x05$_x05$_x05$_x05$_x05$_x05$_x05"
+_x35="$_x05$_x05$_x05$_x05$_x05$_x05$_x05"
+_x40="$_x35$_x05"
 
 # Zero SHA-1
 _z40=0000000000000000000000000000000000000000
@@ -193,7 +194,7 @@ LF='
 # when case-folding filenames
 u200c=$(printf '\342\200\214')
 
-export _x05 _x40 _z40 LF u200c EMPTY_TREE EMPTY_BLOB
+export _x05 _x35 _x40 _z40 LF u200c EMPTY_TREE EMPTY_BLOB
 
 # Each test should start with something like this, after copyright notices:
 #
@@ -600,26 +601,40 @@ test_eval_inner_ () {
 }
 
 test_eval_ () {
-       # We run this block with stderr redirected to avoid extra cruft
-       # during a "-x" trace. Once in "set -x" mode, we cannot prevent
+       # If "-x" tracing is in effect, then we want to avoid polluting stderr
+       # with non-test commands. But once in "set -x" mode, we cannot prevent
        # the shell from printing the "set +x" to turn it off (nor the saving
        # of $? before that). But we can make sure that the output goes to
        # /dev/null.
        #
-       # The test itself is run with stderr put back to &4 (so either to
-       # /dev/null, or to the original stderr if --verbose was used).
+       # There are a few subtleties here:
+       #
+       #   - we have to redirect descriptor 4 in addition to 2, to cover
+       #     BASH_XTRACEFD
+       #
+       #   - the actual eval has to come before the redirection block (since
+       #     it needs to see descriptor 4 to set up its stderr)
+       #
+       #   - likewise, any error message we print must be outside the block to
+       #     access descriptor 4
+       #
+       #   - checking $? has to come immediately after the eval, but it must
+       #     be _inside_ the block to avoid polluting the "set -x" output
+       #
+
+       test_eval_inner_ "$@" </dev/null >&3 2>&4
        {
-               test_eval_inner_ "$@" </dev/null >&3 2>&4
                test_eval_ret_=$?
                if want_trace
                then
                        set +x
-                       if test "$test_eval_ret_" != 0
-                       then
-                               say_color error >&4 "error: last command exited with \$?=$test_eval_ret_"
-                       fi
                fi
-       } 2>/dev/null
+       } 2>/dev/null 4>&2
+
+       if test "$test_eval_ret_" != 0 && want_trace
+       then
+               say_color error >&4 "error: last command exited with \$?=$test_eval_ret_"
+       fi
        return $test_eval_ret_
 }