feature-flags.ts

import * as fs from "fs";
import * as path from "path";

import * as semver from "semver";

import { getApiClient } from "./api-client";
import { CodeQL } from "./codeql";
import * as defaults from "./defaults.json"; // Referenced from codeql-action-sync-tool!
import { Logger } from "./logging";
import { RepositoryNwo } from "./repository";
import * as util from "./util";

const DEFAULT_VERSION_FEATURE_FLAG_PREFIX = "default_codeql_version_";
const DEFAULT_VERSION_FEATURE_FLAG_SUFFIX = "_enabled";
const MINIMUM_ENABLED_CODEQL_VERSION = "2.11.6";

export type CodeQLDefaultVersionInfo =
  | {
      cliVersion: string;
      variant: util.GitHubVariant.DOTCOM;
    }
  | {
      cliVersion: string;
      tagName: string;
      variant: util.GitHubVariant.GHAE | util.GitHubVariant.GHES;
    };

export interface FeatureEnablement {
  /** Gets the default version of the CodeQL tools. */
  getDefaultCliVersion(
    variant: util.GitHubVariant
  ): Promise<CodeQLDefaultVersionInfo>;
  getValue(feature: Feature, codeql?: CodeQL): Promise<boolean>;
}

export enum Feature {
  BypassToolcacheEnabled = "bypass_toolcache_enabled",
  BypassToolcacheKotlinSwiftEnabled = "bypass_toolcache_kotlin_swift_enabled",
  CliConfigFileEnabled = "cli_config_file_enabled",
  DisableKotlinAnalysisEnabled = "disable_kotlin_analysis_enabled",
  MlPoweredQueriesEnabled = "ml_powered_queries_enabled",
  TrapCachingEnabled = "trap_caching_enabled",
  UploadFailedSarifEnabled = "upload_failed_sarif_enabled",
}

export const featureConfig: Record<
  Feature,
  { envVar: string; minimumVersion: string | undefined }
> = {
  [Feature.BypassToolcacheEnabled]: {
    envVar: "CODEQL_BYPASS_TOOLCACHE",
    // Cannot specify a minimum version because this flag is checked before we have
    // access to the CodeQL instance.
    minimumVersion: undefined,
  },
  [Feature.BypassToolcacheKotlinSwiftEnabled]: {
    envVar: "CODEQL_BYPASS_TOOLCACHE_KOTLIN_SWIFT",
    // Cannot specify a minimum version because this flag is checked before we have
    // access to the CodeQL instance.
    minimumVersion: undefined,
  },
  [Feature.DisableKotlinAnalysisEnabled]: {
    envVar: "CODEQL_DISABLE_KOTLIN_ANALYSIS",
    minimumVersion: undefined,
  },
  [Feature.CliConfigFileEnabled]: {
    envVar: "CODEQL_PASS_CONFIG_TO_CLI",
    minimumVersion: "2.11.6",
  },
  [Feature.MlPoweredQueriesEnabled]: {
    envVar: "CODEQL_ML_POWERED_QUERIES",
    minimumVersion: "2.7.5",
  },
  [Feature.TrapCachingEnabled]: {
    envVar: "CODEQL_TRAP_CACHING",
    minimumVersion: undefined,
  },
  [Feature.UploadFailedSarifEnabled]: {
    envVar: "CODEQL_ACTION_UPLOAD_FAILED_SARIF",
    minimumVersion: "2.11.3",
  },
};

/**
 * A response from the GitHub API that contains feature flag enablement information for the CodeQL
 * Action.
 *
 * It maps feature flags to whether they are enabled or not.
 */
type GitHubFeatureFlagsApiResponse = Partial<Record<Feature, boolean>>;

export const FEATURE_FLAGS_FILE_NAME = "cached-feature-flags.json";

/**
 * Determines the enablement status of a number of features.
 * If feature enablement is not able to be determined locally, a request to the
 * GitHub API is made to determine the enablement status.
 */
export class Features implements FeatureEnablement {
  private gitHubFeatureFlags: GitHubFeatureFlags;

  constructor(
    gitHubVersion: util.GitHubVersion,
    repositoryNwo: RepositoryNwo,
    tempDir: string,
    logger: Logger
  ) {
    this.gitHubFeatureFlags = new GitHubFeatureFlags(
      gitHubVersion,
      repositoryNwo,
      path.join(tempDir, FEATURE_FLAGS_FILE_NAME),
      logger
    );
  }

  async getDefaultCliVersion(
    variant: util.GitHubVariant
  ): Promise<CodeQLDefaultVersionInfo> {
    return await this.gitHubFeatureFlags.getDefaultCliVersion(variant);
  }

  /**
   *
   * @param feature The feature to check.
   * @param codeql An optional CodeQL object. If provided, and a `minimumVersion` is specified for the
   *        feature, the version of the CodeQL CLI will be checked against the minimum version.
   *        If the version is less than the minimum version, the feature will be considered
   *        disabled. If not provided, and a `minimumVersion` is specified for the feature, the
   *        this function will throw.
   * @returns true if the feature is enabled, false otherwise.
   *
   * @throws if a `minimumVersion` is specified for the feature, and `codeql` is not provided.
   */
  async getValue(feature: Feature, codeql?: CodeQL): Promise<boolean> {
    if (!codeql && featureConfig[feature].minimumVersion) {
      throw new Error(
        `Internal error: A minimum version is specified for feature ${feature}, but no instance of CodeQL was provided.`
      );
    }

    // Bypassing the toolcache is disabled in test mode.
    if (feature === Feature.BypassToolcacheEnabled && util.isInTestMode()) {
      return false;
    }

    const envVar = (
      process.env[featureConfig[feature].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 = featureConfig[feature].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.
    return await this.gitHubFeatureFlags.getValue(feature);
  }
}

class GitHubFeatureFlags implements FeatureEnablement {
  private cachedApiResponse: GitHubFeatureFlagsApiResponse | undefined;

  constructor(
    private readonly gitHubVersion: util.GitHubVersion,
    private readonly repositoryNwo: RepositoryNwo,
    private readonly featureFlagsFile: string,
    private readonly logger: Logger
  ) {
    /**/
  }

  private getCliVersionFromFeatureFlag(f: string): string | undefined {
    if (
      !f.startsWith(DEFAULT_VERSION_FEATURE_FLAG_PREFIX) ||
      !f.endsWith(DEFAULT_VERSION_FEATURE_FLAG_SUFFIX)
    ) {
      return undefined;
    }
    const version = f
      .substring(
        DEFAULT_VERSION_FEATURE_FLAG_PREFIX.length,
        f.length - DEFAULT_VERSION_FEATURE_FLAG_SUFFIX.length
      )
      .replace(/_/g, ".");

    if (!semver.valid(version)) {
      this.logger.warning(
        `Ignoring feature flag ${f} as it does not specify a valid CodeQL version.`
      );
      return undefined;
    }
    return version;
  }

  async getDefaultCliVersion(
    variant: util.GitHubVariant
  ): Promise<CodeQLDefaultVersionInfo> {
    if (variant === util.GitHubVariant.DOTCOM) {
      return {
        cliVersion: await this.getDefaultDotcomCliVersion(),
        variant,
      };
    }
    return {
      cliVersion: defaults.cliVersion,
      tagName: defaults.bundleVersion,
      variant,
    };
  }

  async getDefaultDotcomCliVersion(): Promise<string> {
    const response = await this.getAllFeatures();

    const enabledFeatureFlagCliVersions = Object.entries(response)
      .map(([f, isEnabled]) =>
        isEnabled ? this.getCliVersionFromFeatureFlag(f) : undefined
      )
      .filter((f) => f !== undefined)
      .map((f) => f as string);

    if (enabledFeatureFlagCliVersions.length === 0) {
      this.logger.debug(
        "Feature flags do not specify a default CLI version. Falling back to CLI version " +
          `${MINIMUM_ENABLED_CODEQL_VERSION}.`
      );
      return MINIMUM_ENABLED_CODEQL_VERSION;
    }

    const maxCliVersion = enabledFeatureFlagCliVersions.reduce(
      (maxVersion, currentVersion) =>
        currentVersion > maxVersion ? currentVersion : maxVersion,
      enabledFeatureFlagCliVersions[0]
    );
    this.logger.debug(
      `Derived default CLI version of ${maxCliVersion} from feature flags.`
    );
    return maxCliVersion;
  }

  async getValue(feature: Feature): Promise<boolean> {
    const response = await this.getAllFeatures();
    if (response === undefined) {
      this.logger.debug(
        `No feature flags API response for ${feature}, considering it disabled.`
      );
      return false;
    }
    const featureEnablement = response[feature];
    if (featureEnablement === undefined) {
      this.logger.debug(
        `Feature '${feature}' undefined in API response, considering it disabled.`
      );
      return false;
    }
    return !!featureEnablement;
  }

  private async getAllFeatures(): Promise<GitHubFeatureFlagsApiResponse> {
    // if we have an in memory cache, use that
    if (this.cachedApiResponse !== undefined) {
      return this.cachedApiResponse;
    }

    // if a previous step has written a feature flags file to disk, use that
    const fileFlags = await this.readLocalFlags();
    if (fileFlags !== undefined) {
      this.cachedApiResponse = fileFlags;
      return fileFlags;
    }

    // if not, request flags from the server
    let remoteFlags = await this.loadApiResponse();
    if (remoteFlags === undefined) {
      remoteFlags = {};
    }

    // cache the response in memory
    this.cachedApiResponse = remoteFlags;

    // and cache them to disk so future workflow steps can use them
    await this.writeLocalFlags(remoteFlags);

    return remoteFlags;
  }

  private async readLocalFlags(): Promise<
    GitHubFeatureFlagsApiResponse | undefined
  > {
    try {
      if (fs.existsSync(this.featureFlagsFile)) {
        this.logger.debug(
          `Loading feature flags from ${this.featureFlagsFile}`
        );
        return JSON.parse(fs.readFileSync(this.featureFlagsFile, "utf8"));
      }
    } catch (e) {
      this.logger.warning(
        `Error reading cached feature flags file ${this.featureFlagsFile}: ${e}. Requesting from GitHub instead.`
      );
    }
    return undefined;
  }

  private async writeLocalFlags(
    flags: GitHubFeatureFlagsApiResponse
  ): Promise<void> {
    try {
      this.logger.debug(`Writing feature flags to ${this.featureFlagsFile}`);
      fs.writeFileSync(this.featureFlagsFile, JSON.stringify(flags));
    } catch (e) {
      this.logger.warning(
        `Error writing cached feature flags file ${this.featureFlagsFile}: ${e}.`
      );
    }
  }

  private async loadApiResponse(): Promise<GitHubFeatureFlagsApiResponse> {
    // Do nothing when not running against github.com
    if (this.gitHubVersion.type !== util.GitHubVariant.DOTCOM) {
      this.logger.debug(
        "Not running against github.com. Disabling all toggleable features."
      );
      return {};
    }
    try {
      const response = await getApiClient().request(
        "GET /repos/:owner/:repo/code-scanning/codeql-action/features",
        {
          owner: this.repositoryNwo.owner,
          repo: this.repositoryNwo.repo,
        }
      );
      const remoteFlags = response.data;
      this.logger.debug(
        "Loaded the following default values for the feature flags from the Code Scanning API: " +
          `${JSON.stringify(remoteFlags)}`
      );
      return remoteFlags;
    } catch (e) {
      if (util.isHTTPError(e) && e.status === 403) {
        this.logger.warning(
          "This run of the CodeQL Action does not have permission to access Code Scanning API endpoints. " +
            "As a result, it will not be opted into any experimental features. " +
            "This could be because the Action is running on a pull request from a fork. If not, " +
            `please ensure the Action has the 'security-events: write' permission. Details: ${e}`
        );
        return {};
      } else {
        // Some features, such as `ml_powered_queries_enabled` affect the produced alerts.
        // Considering these features disabled in the event of a transient error could
        // therefore lead to alert churn. As a result, we crash if we cannot determine the value of
        // the feature.
        throw new Error(
          `Encountered an error while trying to determine feature enablement: ${e}`
        );
      }
    }
  }
}