[MM-64296] Help for AI: Respect env overrides for consoleLevel (#31278)

* respect env overrides for consoleLevel; add tests

* clean up test

* merge conflict

* improve parallelizability

* be better commenting

* better name for fn, comment explaining why we're using it

* empty

* empty

* empty

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/api4/apitestlib_test.go

@@ -0,0 +1,70 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package api4
+
+import (
+	"os"
+	"testing"
+
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEnvironmentVariableHandling(t *testing.T) {
+	// TestEnvironmentVariableHandling should NEVER be run with t.Parallel()
+
+	originalConsoleLevel := os.Getenv("MM_LOGSETTINGS_CONSOLELEVEL")
+	defer func() {
+		// Restore original environment variables
+		if originalConsoleLevel != "" {
+			os.Setenv("MM_LOGSETTINGS_CONSOLELEVEL", originalConsoleLevel)
+		} else {
+			os.Unsetenv("MM_LOGSETTINGS_CONSOLELEVEL")
+		}
+	}()
+
+	t.Run("MM_LOGSETTINGS_CONSOLELEVEL should be respected when set", func(t *testing.T) {
+		// never run with t.Parallel()
+
+		// Set the console level environment variable
+		os.Setenv("MM_LOGSETTINGS_CONSOLELEVEL", "ERROR")
+		defer os.Unsetenv("MM_LOGSETTINGS_CONSOLELEVEL")
+
+		th := SetupEnterprise(t)
+		defer th.TearDown()
+
+		// Verify the console level was set from the environment variable
+		config := th.App.Config()
+		assert.Equal(t, "ERROR", *config.LogSettings.ConsoleLevel)
+	})
+
+	t.Run("Only MM_LOGSETTINGS_CONSOLELEVEL is manually processed", func(t *testing.T) {
+		// never run with t.Parallel()
+
+		// This test verifies that we haven't accidentally enabled general environment
+		// variable processing - we only manually handle MM_LOGSETTINGS_CONSOLELEVEL
+
+		// First, test without MM_LOGSETTINGS_CONSOLELEVEL set
+		os.Unsetenv("MM_LOGSETTINGS_CONSOLELEVEL")
+
+		th1 := SetupEnterprise(t)
+		config1 := th1.App.Config()
+		defaultConsoleLevel := *config1.LogSettings.ConsoleLevel
+		th1.TearDown()
+
+		// Now test with MM_LOGSETTINGS_CONSOLELEVEL set
+		os.Setenv("MM_LOGSETTINGS_CONSOLELEVEL", "DEBUG")
+		defer os.Unsetenv("MM_LOGSETTINGS_CONSOLELEVEL")
+
+		th2 := SetupEnterprise(t)
+		config2 := th2.App.Config()
+		customConsoleLevel := *config2.LogSettings.ConsoleLevel
+		th2.TearDown()
+
+		// Verify our manual implementation works
+		assert.Equal(t, mlog.LvlStdLog.Name, defaultConsoleLevel, "Default should be stdlog")
+		assert.Equal(t, "DEBUG", customConsoleLevel, "Environment variable should be respected")
+		assert.NotEqual(t, defaultConsoleLevel, customConsoleLevel, "Values should be different")
+	})
+}