fix: support special chars in assert_contains expected expression (#426)

See aspect-build/rules_js#1045

lib/testing.bzl

@@ -22,24 +22,31 @@ def assert_contains(name, actual, expected, size = None, timeout = None, **kwarg
     """
 
     test_sh = "_{}_test.sh".format(name)
+    expected_file = "_{}_expected.txt".format(name)
+
+    write_file(
+        name = "_%s_expected" % name,
+        out = expected_file,
+        content = [expected],
+    )
 
     write_file(
         name = "_" + name,
         out = test_sh,
         content = [
             "#!/usr/bin/env bash",
             "set -o errexit",
-            "grep --fixed-strings '{}' $1".format(expected),
+            "grep --fixed-strings -f $1 $2",
         ],
     )
 
     native.sh_test(
         name = name,
         srcs = [test_sh],
-        args = ["$(rootpath %s)" % actual],
+        args = ["$(rootpath %s)" % expected_file, "$(rootpath %s)" % actual],
         size = size,
         timeout = default_timeout(size, timeout),
-        data = [actual],
+        data = [actual, expected_file],
         **kwargs
     )
 

lib/tests/assert_contains/BUILD.bazel

@@ -0,0 +1,21 @@
+load("//lib:testing.bzl", "assert_contains")
+
+# Special characters within expected string: https://github.com/aspect-build/rules_js/issues/1045
+
+assert_contains(
+    name = "regexy-args-1",
+    actual = ":case1.txt",
+    expected = "--arg1='/{{[{]?(.*?)[}]?}}/'",
+)
+
+assert_contains(
+    name = "regexy-args-2",
+    actual = ":case1.txt",
+    expected = "--arg2='/{%(.*?)%}/'",
+)
+
+assert_contains(
+    name = "backtick",
+    actual = ":case1.txt",
+    expected = "`ff`",
+)

lib/tests/assert_contains/case1.txt

@@ -0,0 +1,3 @@
+--arg1='/{{[{]?(.*?)[}]?}}/'
+--arg2='/{%(.*?)%}/'
+`ff`