bazel: add custom shadow lint

BUILD.bazel

@@ -169,9 +169,6 @@ nogo(
             "@org_golang_x_tools//go/analysis/passes/nilness:go_default_library",
             "@org_golang_x_tools//go/analysis/passes/pkgfact:go_default_library",
             "@org_golang_x_tools//go/analysis/passes/printf:go_default_library",
-            # TODO(ricky): we do want to run the shadow check, we just want to exclude
-            # shadows of the variable "err". Presumably we can hack around this. #73069
-            # "@org_golang_x_tools//go/analysis/passes/shadow:go_default_library",
             "@org_golang_x_tools//go/analysis/passes/shift:go_default_library",
             "@org_golang_x_tools//go/analysis/passes/sortslice:go_default_library",
             "@org_golang_x_tools//go/analysis/passes/stdmethods:go_default_library",
@@ -196,6 +193,7 @@ nogo(
             "//pkg/testutils/lint/passes/nocopy",
             "//pkg/testutils/lint/passes/returncheck",
             "//pkg/testutils/lint/passes/returnerrcheck",
+            "//pkg/testutils/lint/passes/shadow",
             "//pkg/testutils/lint/passes/timer",
             "//pkg/testutils/lint/passes/unconvert",
         ] + STATICCHECK_CHECKS,

build/bazelutil/nogo_config.json

@@ -1653,6 +1653,11 @@
             "cockroach/pkg/.*$": "first-party code"
         }
     },
+    "shadow": {
+        "only_files": {
+            "cockroach/pkg/.*$": "first-party code"
+        }
+    },
     "stdmethods": {
         "only_files": {
             "cockroach/pkg/.*$": "first-party code"

pkg/testutils/lint/passes/shadow/BUILD.bazel

@@ -0,0 +1,12 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "shadow",
+    srcs = ["shadow.go"],
+    importpath = "github.com/cockroachdb/cockroach/pkg/testutils/lint/passes/shadow",
+    visibility = ["//visibility:public"],
+    deps = [
+        "@org_golang_x_tools//go/analysis",
+        "@org_golang_x_tools//go/analysis/passes/shadow",
+    ],
+)

pkg/testutils/lint/passes/shadow/shadow.go

@@ -0,0 +1,53 @@
+// Copyright 2022 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+// Package shadow defines an Analyzer that is a slightly modified version
+// of the shadow Analyzer from upstream (golang.org/x/tools).
+// We allow shadows of a few variable names, like err.
+
+//go:build bazel
+// +build bazel
+
+package shadow
+
+import (
+	"fmt"
+	"strings"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/shadow"
+)
+
+var (
+	Analyzer         = shadow.Analyzer
+	permittedShadows = []string{
+		"ctx",
+		"err",
+		"pErr",
+	}
+)
+
+func init() {
+	oldRun := Analyzer.Run
+	Analyzer.Run = func(p *analysis.Pass) (interface{}, error) {
+		pass := *p
+		oldReport := p.Report
+		pass.Report = func(diag analysis.Diagnostic) {
+			for _, permittedShadow := range permittedShadows {
+				if strings.HasPrefix(diag.Message, fmt.Sprintf("declaration of %q shadows declaration at line", permittedShadow)) {
+					// Can throw the failure away.
+					return
+				}
+			}
+			oldReport(diag)
+		}
+		return oldRun(&pass)
+	}
+}

pkg/testutils/lint/passes/shadow/shadow_no_bazel.go

@@ -0,0 +1,18 @@
+// Copyright 2022 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+// Package shadow is empty when not built under Bazel.
+
+//go:build !bazel
+// +build !bazel
+
+package shadow
+
+// File intentionally empty.

pkg/util/log/eventpb/gen.go

@@ -387,10 +387,11 @@ func readInput(
 				// redact:"safeif:<regexp>" - safe for reporting if the string matches the regexp.
 				safeReName := ""
 				if re := fieldDefRe.ReplaceAllString(line, "$safeif"); re != "" {
+					var err error
 					// We're reading the regular expression from the .proto source, so we must
 					// take care of string un-escaping ourselves. If this code ever improves
 					// to apply as a protobuf plugin, this step can be removed.
-					re, err := strconv.Unquote(`"` + re + `"`)
+					re, err = strconv.Unquote(`"` + re + `"`)
 					if err != nil {
 						return errors.Wrapf(err, "error while unquoting regexp at %q", line)
 					}