Define a should_color library

Honors NO_COLOR, FORCE_COLOR, and defaults to whether the terminal is
interactive.

Bug: b/533162913

Author: Databean

base/cvd/cuttlefish/ansi_codes/BUILD.bazel

@@ -13,6 +13,15 @@ cf_cc_library(
     ],
 )
 
+cf_cc_library(
+    name = "should_color",
+    srcs = ["should_color.cc"],
+    hdrs = ["should_color.h"],
+    deps = [
+        "//cuttlefish/common/libs/utils:environment",
+    ],
+)
+
 cf_cc_library(
     name = "terminal_colors",
     srcs = ["terminal_colors.cc"],

base/cvd/cuttlefish/ansi_codes/should_color.cc

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2026 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "cuttlefish/ansi_codes/should_color.h"
+
+#include <unistd.h>
+
+#include "cuttlefish/common/libs/utils/environment.h"
+
+namespace cuttlefish {
+namespace {
+
+bool ColorDefault(int fd) {
+  // https://no-color.org/
+  if (!StringFromEnv("NO_COLOR").value_or("").empty()) {
+    return false;
+  }
+  // https://force-color.org/
+  if (!StringFromEnv("FORCE_COLOR").value_or("").empty()) {
+    return true;
+  }
+  return isatty(fd);
+}
+
+}  // namespace
+
+bool ShouldColorStdout() { return ColorDefault(STDOUT_FILENO); }
+
+bool ShouldColorStderr() { return ColorDefault(STDERR_FILENO); }
+
+}  // namespace cuttlefish

base/cvd/cuttlefish/ansi_codes/should_color.h

@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2026 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#pragma once
+
+namespace cuttlefish {
+
+bool ShouldColorStdout();
+bool ShouldColorStderr();
+
+}  // namespace cuttlefish