Refactor handling of feature flags

This commit centralizes how feature flags are handled. All feature flags
must now add an entry in the `featureFlagConfig` dictionary. This
dictionary associates the flag with an environment variable name and
optionally a minimum version for CodeQL.

The new logic is:

- if the environment variable is set to false: disabled
- if the minimum version requirement specified and met: disabled
- if the environment variable is set to true: enable
- Otherwise check feature flag enablement from the server

lib/feature-flags.js

@@ -19,7 +19,7 @@ var __importStar = (this && this.__importStar) || function (mod) {
     return result;
 };
 Object.defineProperty(exports, "__esModule", { value: true });
-exports.createFeatureFlags = exports.GitHubFeatureFlags = exports.FeatureFlag = void 0;
+exports.createFeatureFlags = exports.GitHubFeatureFlags = exports.featureFlagConfig = exports.FeatureFlag = void 0;
 const api_client_1 = require("./api-client");
 const util = __importStar(require("./util"));
 var FeatureFlag;
@@ -30,6 +30,28 @@ var FeatureFlag;
     FeatureFlag["GolangExtractionReconciliationEnabled"] = "golang_extraction_reconciliation_enabled";
     FeatureFlag["CliConfigFileEnabled"] = "cli_config_file_enabled";
 })(FeatureFlag = exports.FeatureFlag || (exports.FeatureFlag = {}));
+exports.featureFlagConfig = {
+    [FeatureFlag.BypassToolcacheEnabled]: {
+        envVar: "CODEQL_BYPASS_TOOLCACHE",
+        minimumVersion: undefined,
+    },
+    [FeatureFlag.MlPoweredQueriesEnabled]: {
+        envVar: "CODEQL_VERSION_ML_POWERED_QUERIES",
+        minimumVersion: "2.7.5",
+    },
+    [FeatureFlag.TrapCachingEnabled]: {
+        envVar: "CODEQL_TRAP_CACHING",
+        minimumVersion: undefined,
+    },
+    [FeatureFlag.GolangExtractionReconciliationEnabled]: {
+        envVar: "CODEQL_GOLANG_EXTRACTION_RECONCILIATION",
+        minimumVersion: undefined,
+    },
+    [FeatureFlag.CliConfigFileEnabled]: {
+        envVar: "CODEQL_PASS_CONFIG_TO_CLI",
+        minimumVersion: "2.10.1",
+    },
+};
 class GitHubFeatureFlags {
     constructor(gitHubVersion, apiDetails, repositoryNwo, logger) {
         this.gitHubVersion = gitHubVersion;
@@ -37,11 +59,28 @@ class GitHubFeatureFlags {
         this.repositoryNwo = repositoryNwo;
         this.logger = logger;
     }
-    async getValue(flag) {
+    async getValue(flag, codeql) {
         // Bypassing the toolcache is disabled in test mode.
         if (flag === FeatureFlag.BypassToolcacheEnabled && util.isInTestMode()) {
             return false;
         }
+        const envVar = (process.env[exports.featureFlagConfig[flag].envVar] || "").toLocaleLowerCase();
+        // Do not use this feature if user explicitly disables it via an environment variable.
+        if (envVar === "false") {
+            return false;
+        }
+        // Never use this feature if the CLI version explicitly can't support it.
+        const minimumVersion = exports.featureFlagConfig[flag].minimumVersion;
+        if (codeql && minimumVersion) {
+            if (!(await util.codeQlVersionAbove(codeql, minimumVersion))) {
+                return false;
+            }
+        }
+        // Use this feature if user explicitly enables it via an environment variable.
+        if (envVar === "true") {
+            return true;
+        }
+        // Ask the GitHub API if the feature is enabled.
         const response = await this.getApiResponse();
         if (response === undefined) {
             this.logger.debug(`No feature flags API response for ${flag}, considering it disabled.`);