Remove cgo from coverage test (#1483)

I no longer believe there is a way to consistently collect coverage
data for C libraries with Bazel. This test kept getting stuck in good
or bad states, and its success depended on other tests that were
running with it and tools (lcov) installed on the system.

cgo coverage won't be supported until this is fixed in Bazel.

Also:

Deleted coverage_bin_test since it's expensive to run and provides
very little value.

tests/core/coverage/BUILD.bazel

@@ -36,12 +36,9 @@ function check_file_excluded {
 included_files=(
   'github.com/bazelbuild/rules_go/tests/core/coverage/a/a.go:'
   'github.com/bazelbuild/rules_go/tests/core/coverage/c/c.go:'
-  'github.com/bazelbuild/rules_go/tests/core/coverage/c/c_cgo.go:'
 )
 excluded_files=(
   'github.com/bazelbuild/rules_go/tests/core/coverage/b/b.go:'
-  'github.com/bazelbuild/rules_go/tests/core/coverage/b/b_cgo.go:'
-  '\.cgo1\.go:'
 )
 for i in "${included_files[@]}"; do
   check_file_included "$i"
@@ -55,10 +52,7 @@ done
         "--instrumentation_filter=-coverage:b",
         "--nocache_test_results",
     ],
-    targets = select({
-        "@io_bazel_rules_go//go/platform:darwin": [],
-        "//conditions:default": [":coverage_test"],
-    }),
+    targets = [":coverage_test"],
 )
 
 go_test(
@@ -68,61 +62,22 @@ go_test(
     tags = ["manual"],
 )
 
-bazel_test(
-    name = "coverage_bin_test",
-    check = """
-no_tests_found=4
-if [ "$result" -ne "$no_tests_found" ]; then
-  echo "error: unexpected bazel exit code: want $no_tests_found, got $result" >&2
-  exit 1
-fi
-result=0
-""",
-    command = "coverage",
-    targets = select({
-        # TODO(bazelbuild/bazel#5128): skip coverage test on Darwin. The target
-        # includes cgo, which gets instrumented, and Bazel reports link errors
-        # for instrumented C code on Darwin.
-        "@io_bazel_rules_go//go/platform:darwin": [],
-        "//conditions:default": [":coverage_bin"],
-    }),
-)
-
-go_binary(
-    name = "coverage_bin",
-    srcs = ["coverage_bin.go"],
-    deps = [":a"],
-    tags = ["manual"],
-)
-
 go_library(
     name = "a",
-    srcs = [
-        "a.go",
-        "a_cgo.go",
-    ],
-    cgo = True,
+    srcs = ["a.go"],
     deps = [":b"],
     importpath = "github.com/bazelbuild/rules_go/tests/core/coverage/a",
 )
 
 go_library(
     name = "b",
-    srcs = [
-        "b.go",
-        "b_cgo.go",
-    ],
-    cgo = True,
+    srcs = ["b.go"],
     deps = [":c"],
     importpath = "github.com/bazelbuild/rules_go/tests/core/coverage/b",
 )
 
 go_library(
     name = "c",
-    srcs = [
-        "c.go",
-        "c_cgo.go",
-    ],
-    cgo = True,
+    srcs = ["c.go"],
     importpath = "github.com/bazelbuild/rules_go/tests/core/coverage/c",
 )

tests/core/coverage/README.rst

@@ -8,9 +8,3 @@ Checks that ``bazel coverage`` on a ``go_test`` produces reasonable output.
 Libraries referenced by the test that pass ``--instrumentation_filter`` should
 have coverage data. Library excluded with ``--instrumentatiuon_filter`` should
 not have coverage data.
-
-coverage_bin_test
------------------
-
-Checks that ``bazel coverage`` on a ``go_binary`` causes Bazel to exit with
-status 4 (no tests found) instead of some other failure.

tests/core/coverage/coverage_test.go

@@ -4,5 +4,4 @@ import "testing"
 
 func TestLive(t *testing.T) {
 	ALive()
-	ACgoLive()
 }