testing/env: Make @go.test_compgen fail loudly

The previous commit rectified errors in assertions from `tests/new.bats`
whereby assertions that should have failed as written did not. Though
the code under test was sound, these latent test errors were due to the
fact that `@go.test_compgen` would produce an empty result array and
return success if the underlying `@go.compgen` returned empty results.

When this empty array was passed to `assert_success` or `assert_failure`
using "${array[@]}" notation, it expanded to an empty argument list, in
which case these assertions did not check the value of `$output`. This
left the impression that the output matched a nonempty list of values
when the assertions were actually not comparing the output at all.

Now `@go.test_compgen` will fail loudly with `@go.compgen` results are
empty, and any case in which the underlying `@go.compgen` returns an
error.

Author: mbland

lib/testing/environment

@@ -120,8 +120,19 @@ test-go() {
 #   ...:     Arguments passed directly to `@go.compgen`
 @go.test_compgen() {
   set "$DISABLE_BATS_SHELL_OPTIONS"
+  local completions
+  local err_args
+
   . "$_GO_USE_MODULES" 'complete' 'strings'
-  @go.split $'\n' "$(@go.compgen "${@:2}")" "$1"
+  completions="$(@go.compgen "${@:2}")"
+
+  if [[ "$?" -ne '0' || -z "$completions" ]]; then
+    printf -v 'err_args' ' "%s"' "${@:2}"
+    printf 'compgen failed or results were empty:%s\n' "$err_args" >&2
+    restore_bats_shell_options '1'
+    return
+  fi
+  @go.split $'\n' "$completions" "$1"
   restore_bats_shell_options "$?"
 }
 

tests/testing/environment.bats

@@ -93,33 +93,3 @@ teardown() {
   run test-go
   assert_success '_GO_CMD: test-go'
 }
-
-setup_go_test_compgen() {
-  local item
-
-  mkdir -p "$TEST_GO_ROOTDIR/lib"
-  printf 'foo' >"$TEST_GO_ROOTDIR/lib/foo"
-  printf 'bar' >"$TEST_GO_ROOTDIR/lib/bar"
-  printf 'baz' >"$TEST_GO_ROOTDIR/lib/baz"
-
-  . "$_GO_USE_MODULES" 'complete'
-  while IFS= read -r item; do
-    __expected+=("${item#$TEST_GO_ROOTDIR/}")
-  done < <(@go.compgen -f -- "$TEST_GO_ROOTDIR/lib/")
-}
-
-@test "$SUITE: @go.test_compgen" {
-  set "$DISABLE_BATS_SHELL_OPTIONS"
-  local __expected=()
-  setup_go_test_compgen
-  restore_bats_shell_options "$?"
-
-  export -f @go.test_compgen
-  @go.create_test_go_script \
-    'declare results=()' \
-    '@go.test_compgen "results" -f -- lib/' \
-    'printf "%s\n" "${results[@]}"'
-
-  run "$TEST_GO_SCRIPT"
-  assert_success "${__expected[@]}"
-}

tests/testing/environment/test-compgen.bats

@@ -0,0 +1,56 @@
+#! /usr/bin/env bats
+
+load ../../environment
+
+EXPECTED=()
+
+setup() {
+  test_filter
+  @go.create_test_go_script
+  export -f @go.test_compgen
+
+  set "$DISABLE_BATS_SHELL_OPTIONS"
+  setup_go_test_compgen
+  restore_bats_shell_options "$?"
+
+  @go.create_test_go_script \
+    'declare results=()' \
+    'if ! @go.test_compgen "results" "$@"; then' \
+    '  exit 1' \
+    'fi' \
+    'printf "%s\n" "${results[@]}"'
+}
+
+teardown() {
+  @go.remove_test_go_rootdir
+}
+
+setup_go_test_compgen() {
+  local item
+
+  mkdir -p "$TEST_GO_ROOTDIR/lib"
+  printf 'foo' >"$TEST_GO_ROOTDIR/lib/foo"
+  printf 'bar' >"$TEST_GO_ROOTDIR/lib/bar"
+  printf 'baz' >"$TEST_GO_ROOTDIR/lib/baz"
+
+  . "$_GO_USE_MODULES" 'complete'
+  while IFS= read -r item; do
+    EXPECTED+=("${item#$TEST_GO_ROOTDIR/}")
+  done < <(@go.compgen -f -- "$TEST_GO_ROOTDIR/lib/")
+}
+
+@test "$SUITE: completion succeeds" {
+  run "$TEST_GO_SCRIPT" -f -- lib/
+  assert_success "${EXPECTED[@]}"
+}
+
+@test "$SUITE: completion fails" {
+  run "$TEST_GO_SCRIPT" -f -- lib/nonexistent
+  assert_failure \
+    'compgen failed or results were empty: "-f" "--" "lib/nonexistent"'
+}
+
+@test "$SUITE: fails if completions are empty" {
+  run "$TEST_GO_SCRIPT" lib/nonexistent
+  assert_failure 'compgen failed or results were empty: "lib/nonexistent"'
+}