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feat(v2): add IsFeatureEnabled (#454)
Check if an experimental feature is enabled via environment variable. The feature name must be the suffix, e.g., FOO for GOOGLE_SDK_GO_EXPERIMENTAL_FOO.
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‎v2/feature.go‎

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// Copyright 2025, Google Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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package gax
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import (
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"os"
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"strings"
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"sync"
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)
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var (
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// featureEnabledOnce caches results for IsFeatureEnabled.
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featureEnabledOnce sync.Once
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featureEnabledStore map[string]bool
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)
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// IsFeatureEnabled checks if an experimental feature is enabled via
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// environment variable. The environment variable must be prefixed with
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// "GOOGLE_SDK_GO_EXPERIMENTAL_". The feature name passed to this
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// function must be the suffix (e.g., "FOO" for "GOOGLE_SDK_GO_EXPERIMENTAL_FOO").
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// To enable the feature, the environment variable's value must be "true",
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// case-insensitive. The result for each name is cached on the first call.
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func IsFeatureEnabled(name string) bool {
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featureEnabledOnce.Do(func() {
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featureEnabledStore = make(map[string]bool)
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for _, env := range os.Environ() {
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if strings.HasPrefix(env, "GOOGLE_SDK_GO_EXPERIMENTAL_") {
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// Parse "KEY=VALUE"
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kv := strings.SplitN(env, "=", 2)
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if len(kv) == 2 && strings.ToLower(kv[1]) == "true" {
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key := strings.TrimPrefix(kv[0], "GOOGLE_SDK_GO_EXPERIMENTAL_")
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featureEnabledStore[key] = true
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}
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}
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}
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})
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return featureEnabledStore[name]
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}
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// TestOnlyResetIsFeatureEnabled is for testing purposes only. It resets the cached
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// feature flags, allowing environment variables to be re-read on the next call to IsFeatureEnabled.
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// This function is not thread-safe; if another goroutine reads a feature after this
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// function is called but before the `featureEnabledOnce` is re-initialized by IsFeatureEnabled,
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// it may see an inconsistent state.
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func TestOnlyResetIsFeatureEnabled() {
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featureEnabledOnce = sync.Once{}
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featureEnabledStore = nil
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}

‎v2/feature_test.go‎

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// Copyright 2025, Google Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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package gax
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import (
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"os"
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"testing"
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)
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func TestIsFeatureEnabled(t *testing.T) {
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tests := []struct {
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name string
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envVar string
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envValue string
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expected bool
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expectedCache bool
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}{
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{
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name: "EnabledFeature",
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envVar: "GOOGLE_SDK_GO_EXPERIMENTAL_TRACING",
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envValue: "true",
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expected: true,
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expectedCache: true,
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},
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{
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name: "DisabledFeature",
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envVar: "GOOGLE_SDK_GO_EXPERIMENTAL_ANOTHER",
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envValue: "false",
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expected: false,
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expectedCache: false,
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},
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{
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name: "MissingFeature",
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envVar: "GOOGLE_SDK_GO_EXPERIMENTAL_MISSING",
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envValue: "",
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expected: false,
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expectedCache: false,
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},
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{
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name: "CaseInsensitiveTrue",
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envVar: "GOOGLE_SDK_GO_EXPERIMENTAL_MIXED_CASE",
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envValue: "True",
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expected: true,
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expectedCache: true,
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},
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{
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name: "CaseInsensitiveTrue",
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envVar: "GOOGLE_SDK_GO_EXPERIMENTAL_UPPER_CASE",
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envValue: "TRUE",
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expected: true,
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expectedCache: true,
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},
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{
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name: "OtherValue",
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envVar: "GOOGLE_SDK_GO_EXPERIMENTAL_INVALID",
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envValue: "1",
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expected: false,
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expectedCache: false,
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},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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// Reset the global state for each test to ensure isolation
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TestOnlyResetIsFeatureEnabled()
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if tt.envValue != "" {
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os.Setenv(tt.envVar, tt.envValue)
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defer os.Unsetenv(tt.envVar)
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}
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if got := IsFeatureEnabled(tt.envVar[len("GOOGLE_SDK_GO_EXPERIMENTAL_"):]); got != tt.expected {
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t.Errorf("IsFeatureEnabled() = %v, want %v", got, tt.expected)
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}
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// Verify caching behavior after the first call
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if tt.expectedCache && featureEnabledStore[tt.envVar[len("GOOGLE_SDK_GO_EXPERIMENTAL_"):]] != true {
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t.Errorf("Feature %s not correctly cached as true", tt.envVar)
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} else if !tt.expectedCache && featureEnabledStore[tt.envVar[len("GOOGLE_SDK_GO_EXPERIMENTAL_"):]] == true {
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t.Errorf("Feature %s incorrectly cached as true", tt.envVar)
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}
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})
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}
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// Test that subsequent calls to IsFeatureEnabled do not re-read environment variables
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t.Run("CachingPreventsReread", func(t *testing.T) {
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TestOnlyResetIsFeatureEnabled()
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// Set an environment variable for the first call
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os.Setenv("GOOGLE_SDK_GO_EXPERIMENTAL_CACHED_FEATURE", "true")
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defer os.Unsetenv("GOOGLE_SDK_GO_EXPERIMENTAL_CACHED_FEATURE")
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// First call, should read from env and cache
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if !IsFeatureEnabled("CACHED_FEATURE") {
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t.Fatalf("Expected CACHED_FEATURE to be enabled on first call")
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}
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// Unset the environment variable after the first call
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os.Unsetenv("GOOGLE_SDK_GO_EXPERIMENTAL_CACHED_FEATURE")
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// Second call, should use cached value and still be true
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if !IsFeatureEnabled("CACHED_FEATURE") {
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t.Errorf("Expected CACHED_FEATURE to remain enabled due to caching")
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}
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// Check a new feature that was never set, should be false
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if IsFeatureEnabled("NEW_FEATURE_AFTER_CACHE") {
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t.Errorf("Expected NEW_FEATURE_AFTER_CACHE to be false as it was set after init")
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}
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})
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// Test with multiple environment variables set
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t.Run("MultipleEnvVars", func(t *testing.T) {
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TestOnlyResetIsFeatureEnabled()
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os.Setenv("GOOGLE_SDK_GO_EXPERIMENTAL_FEATURE1", "true")
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os.Setenv("GOOGLE_SDK_GO_EXPERIMENTAL_FEATURE2", "false")
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os.Setenv("GOOGLE_SDK_GO_EXPERIMENTAL_FEATURE3", "true")
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defer os.Unsetenv("GOOGLE_SDK_GO_EXPERIMENTAL_FEATURE1")
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defer os.Unsetenv("GOOGLE_SDK_GO_EXPERIMENTAL_FEATURE2")
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defer os.Unsetenv("GOOGLE_SDK_GO_EXPERIMENTAL_FEATURE3")
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if !IsFeatureEnabled("FEATURE1") {
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t.Errorf("Expected FEATURE1 to be enabled")
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}
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if IsFeatureEnabled("FEATURE2") {
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t.Errorf("Expected FEATURE2 to be disabled")
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}
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if !IsFeatureEnabled("FEATURE3") {
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t.Errorf("Expected FEATURE3 to be enabled")
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}
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if IsFeatureEnabled("NONEXISTENT_FEATURE") {
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t.Errorf("Expected NONEXISTENT_FEATURE to be disabled")
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}
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})
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}

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