diff_test: add rule and tests (#136)

This new test rule compares two files and passes
if the files match.

On Linux/macOS/non-Windows, the test compares
files using 'diff'.

On Windows, the test compares files using
'fc.exe'. This utility is available on all Windows
versions I tried (Windows 2008 Server, Windows
2016 Datacenter Core).

See https://github.com/bazelbuild/bazel/issues/5508
See https://github.com/bazelbuild/bazel/issues/4319

5 files changed, 250 insertions, 0 deletions

diff --git a/tests/diff_test/BUILD b/tests/diff_test/BUILD
new file mode 100644
index 0000000..3a33bf2
--- /dev/null
+++ b/tests/diff_test/BUILD
@@ -0,0 +1,42 @@
+# This package aids testing the 'diff_test' rule.
+
+load("//rules:diff_test.bzl", "diff_test")
+
+package(default_testonly = 1)
+
+sh_test(
+    name = "diff_test_tests",
+    srcs = ["diff_test_tests.sh"],
+    data = [
+        "//rules:diff_test",
+        "//tests:unittest.bash",
+    ],
+    deps = ["@bazel_tools//tools/bash/runfiles"],
+)
+
+diff_test(
+    name = "same_src_src",
+    file1 = "a.txt",
+    file2 = "aa.txt",
+)
+
+diff_test(
+    name = "same_src_gen",
+    file1 = "a.txt",
+    file2 = "a-gen.txt",
+)
+
+diff_test(
+    name = "same_gen_gen",
+    file1 = "a-gen.txt",
+    file2 = "aa-gen.txt",
+)
+
+genrule(
+    name = "gen",
+    outs = [
+        "a-gen.txt",
+        "aa-gen.txt",
+    ],
+    cmd = "echo -n 'potato' > $(location a-gen.txt) && echo -n 'potato' > $(location aa-gen.txt)",
+)
diff --git a/tests/diff_test/a.txt b/tests/diff_test/a.txt
new file mode 100644
index 0000000..86ba009
--- /dev/null
+++ b/tests/diff_test/a.txt
@@ -0,0 +1 @@
+potato
\ No newline at end of file
diff --git a/tests/diff_test/aa.txt b/tests/diff_test/aa.txt
new file mode 100644
index 0000000..86ba009
--- /dev/null
+++ b/tests/diff_test/aa.txt
@@ -0,0 +1 @@
+potato
\ No newline at end of file
diff --git a/tests/diff_test/b.txt b/tests/diff_test/b.txt
new file mode 100644
index 0000000..1910281
--- /dev/null
+++ b/tests/diff_test/b.txt
@@ -0,0 +1 @@
+foo
\ No newline at end of file
diff --git a/tests/diff_test/diff_test_tests.sh b/tests/diff_test/diff_test_tests.sh
new file mode 100755
index 0000000..aa43307
--- /dev/null
+++ b/tests/diff_test/diff_test_tests.sh
@@ -0,0 +1,205 @@
+# Copyright 2019 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# --- begin runfiles.bash initialization ---
+# Copy-pasted from Bazel's Bash runfiles library (tools/bash/runfiles/runfiles.bash).
+set -euo pipefail
+if [[ ! -d "${RUNFILES_DIR:-/dev/null}" && ! -f "${RUNFILES_MANIFEST_FILE:-/dev/null}" ]]; then
+  if [[ -f "$0.runfiles_manifest" ]]; then
+    export RUNFILES_MANIFEST_FILE="$0.runfiles_manifest"
+  elif [[ -f "$0.runfiles/MANIFEST" ]]; then
+    export RUNFILES_MANIFEST_FILE="$0.runfiles/MANIFEST"
+  elif [[ -f "$0.runfiles/bazel_tools/tools/bash/runfiles/runfiles.bash" ]]; then
+    export RUNFILES_DIR="$0.runfiles"
+  fi
+fi
+if [[ -f "${RUNFILES_DIR:-/dev/null}/bazel_tools/tools/bash/runfiles/runfiles.bash" ]]; then
+  source "${RUNFILES_DIR}/bazel_tools/tools/bash/runfiles/runfiles.bash"
+elif [[ -f "${RUNFILES_MANIFEST_FILE:-/dev/null}" ]]; then
+  source "$(grep -m1 "^bazel_tools/tools/bash/runfiles/runfiles.bash " \
+            "$RUNFILES_MANIFEST_FILE" | cut -d ' ' -f 2-)"
+else
+  echo >&2 "ERROR: cannot find @bazel_tools//tools/bash/runfiles:runfiles.bash"
+  exit 1
+fi
+# --- end runfiles.bash initialization ---
+
+source "$(rlocation bazel_skylib/tests/unittest.bash)" \
+  || { echo "Could not source bazel_skylib/tests/unittest.bash" >&2; exit 1; }
+
+function import_diff_test() {
+  local -r repo="$1"
+  mkdir -p "${repo}/rules"
+  touch "${repo}/WORKSPACE"
+  ln -sf "$(rlocation bazel_skylib/rules/diff_test.bzl)" \
+         "${repo}/rules/diff_test.bzl"
+  echo "exports_files(['diff_test.bzl'])" > "${repo}/rules/BUILD"
+}
+
+function assert_simple_diff_test() {
+  local -r flag="$1"
+  local -r ws="${TEST_TMPDIR}/$2"
+
+  import_diff_test "$ws"
+  touch "$ws/WORKSPACE"
+  cat >"$ws/BUILD" <<'eof'
+load("//rules:diff_test.bzl", "diff_test")
+
+diff_test(
+    name = "same",
+    file1 = "a.txt",
+    file2 = "a.txt",
+)
+
+diff_test(
+    name = "different",
+    file1 = "a.txt",
+    file2 = "b.txt",
+)
+eof
+  echo foo > "$ws/a.txt"
+  echo bar > "$ws/b.txt"
+
+  (cd "$ws" && \
+   bazel test "$flag" //:same --test_output=errors 1>"$TEST_log" 2>&1 \
+     || fail "expected success")
+
+  (cd "$ws" && \
+   bazel test "$flag" //:different --test_output=errors 1>"$TEST_log" 2>&1 \
+     && fail "expected failure" || true)
+  expect_log 'FAIL: files "a.txt" and "b.txt" differ'
+}
+
+function assert_from_ext_repo() {
+  local -r flag="$1"
+  local -r ws="${TEST_TMPDIR}/$2"
+
+  # Import the rule to an external repository.
+  import_diff_test "$ws/bzl"
+  mkdir -p "$ws/ext1/foo" "$ws/main/ext1/foo" "$ws/ext2/foo" "$ws/main/ext2/foo"
+  cat >"$ws/main/WORKSPACE" <<'eof'
+local_repository(
+    name = "bzl",
+    path = "../bzl",
+)
+
+local_repository(
+    name = "ext1",
+    path = "../ext1",
+)
+
+local_repository(
+    name = "ext2",
+    path = "../ext2",
+)
+eof
+
+  # @ext1 has source files
+  touch "$ws/ext1/WORKSPACE"
+  echo 'exports_files(["foo.txt"])' >"$ws/ext1/foo/BUILD"
+  echo 'foo' > "$ws/ext1/foo/foo.txt"
+
+  # @//ext1/foo has different files than @ext1//foo
+  echo 'exports_files(["foo.txt"])' >"$ws/main/ext1/foo/BUILD"
+  echo 'not foo' > "$ws/main/ext1/foo/foo.txt"
+
+  # @ext2 has generated files
+  touch "$ws/ext2/WORKSPACE"
+  cat >"$ws/ext2/foo/BUILD" <<'eof'
+genrule(
+    name = "gen",
+    outs = [
+        "foo.txt",
+        "bar.txt",
+    ],
+    cmd = "echo 'foo' > $(location foo.txt) && echo 'bar' > $(location bar.txt)",
+    visibility = ["//visibility:public"],
+)
+eof
+
+  # @//ext2/foo has different files than @ext2//foo
+  cat >"$ws/main/ext2/foo/BUILD" <<'eof'
+genrule(
+    name = "gen",
+    outs = ["foo.txt"],
+    cmd = "echo 'not foo' > $@",
+    visibility = ["//visibility:public"],
+)
+eof
+
+  cat >"$ws/main/BUILD" <<'eof'
+load("@bzl//rules:diff_test.bzl", "diff_test")
+
+diff_test(
+    name = "same",
+    file1 = "@ext1//foo:foo.txt",
+    file2 = "@ext2//foo:foo.txt",
+)
+
+diff_test(
+    name = "different1",
+    file1 = "@ext1//foo:foo.txt",
+    file2 = "@ext2//foo:bar.txt",
+)
+
+diff_test(
+    name = "different2",
+    file1 = "@ext1//foo:foo.txt",
+    file2 = "//ext1/foo:foo.txt",
+)
+
+diff_test(
+    name = "different3",
+    file1 = "//ext2/foo:foo.txt",
+    file2 = "@ext2//foo:foo.txt",
+)
+eof
+
+  (cd "$ws/main" && \
+   bazel test "$flag" //:same --test_output=errors 1>"$TEST_log" 2>&1 \
+     || fail "expected success")
+
+  (cd "$ws/main" && \
+   bazel test "$flag" //:different1 --test_output=errors 1>"$TEST_log" 2>&1 \
+     && fail "expected failure" || true)
+  expect_log 'FAIL: files "external/ext1/foo/foo.txt" and "external/ext2/foo/bar.txt" differ'
+
+  (cd "$ws/main" && \
+   bazel test "$flag" //:different2 --test_output=errors 1>"$TEST_log" 2>&1 \
+     && fail "expected failure" || true)
+  expect_log 'FAIL: files "external/ext1/foo/foo.txt" and "ext1/foo/foo.txt" differ'
+
+  (cd "$ws/main" && \
+   bazel test "$flag" //:different3 --test_output=errors 1>"$TEST_log" 2>&1 \
+     && fail "expected failure" || true)
+  expect_log 'FAIL: files "ext2/foo/foo.txt" and "external/ext2/foo/foo.txt" differ'
+}
+
+function test_simple_diff_test_with_legacy_external_runfiles() {
+  assert_simple_diff_test "--legacy_external_runfiles" "${FUNCNAME[0]}"
+}
+
+function test_simple_diff_test_without_legacy_external_runfiles() {
+  assert_simple_diff_test "--nolegacy_external_runfiles" "${FUNCNAME[0]}"
+}
+
+function test_from_ext_repo_with_legacy_external_runfiles() {
+  assert_from_ext_repo "--legacy_external_runfiles" "${FUNCNAME[0]}"
+}
+
+function test_from_ext_repo_without_legacy_external_runfiles() {
+  assert_from_ext_repo "--nolegacy_external_runfiles" "${FUNCNAME[0]}"
+}
+
+run_suite "diff_test_tests test suite"