Fix race condition when generating evaluator log summaries

The original code that logged the human-readable log summary generated the log asynchronously, which was a reasonable choice. When I added support for viewing and scanning logs, I didn't notice that the summary was being generated asynchronously, and wrote my code assuming that the summary was already on disk when I opened it to find where each relation's log started. The effect was that, depending on timing, the evaluation sometimes failed with an error popup complaining about not being able to open the log summary file.

The fix is to _generate_ the log summary synchronously, but continue to _log_ it asynchronously.

Author: Dave Bartolomeo

extensions/ql-vscode/src/run-queries.ts

@@ -36,7 +36,7 @@ import { compileDatabaseUpgradeSequence, hasNondestructiveUpgradeCapabilities, u
 import { ensureMetadataIsComplete } from './query-results';
 import { SELECT_QUERY_NAME } from './contextual/locationFinder';
 import { DecodedBqrsChunk } from './pure/bqrs-cli-types';
-import { getErrorMessage } from './pure/helpers-pure';
+import { asError, getErrorMessage } from './pure/helpers-pure';
 import { generateSummarySymbolsFile } from './log-insights/summary-parser';
 
 /**
@@ -207,7 +207,10 @@ export class QueryEvaluationInfo {
           logPath: this.evalLogPath,
         });
         if (await this.hasEvalLog()) {
-          this.displayHumanReadableLogSummary(queryInfo, qs);
+          queryInfo.evalLogLocation = this.evalLogPath;
+          queryInfo.evalLogSummaryLocation = await this.generateHumanReadableLogSummary(qs);
+          void this.logEndSummary(queryInfo.evalLogSummaryLocation, qs);  // Logged asynchrnously
+
           if (config.isCanary()) { // Generate JSON summary for viewer.
             await qs.cliServer.generateJsonLogSummary(this.evalLogPath, this.jsonEvalLogSummaryPath);
             queryInfo.jsonEvalLogSummaryLocation = this.jsonEvalLogSummaryPath;
@@ -340,25 +343,40 @@ export class QueryEvaluationInfo {
   }
 
   /**
-   * Calls the appropriate CLI command to generate a human-readable log summary
-   * and logs to the Query Server console and query log file.
+   * Calls the appropriate CLI command to generate a human-readable log summary.
+   * @param qs The query server client.
+   * @returns The path to the log summary, or `undefined` if the summary could not be generated.
    */
-  displayHumanReadableLogSummary(queryInfo: LocalQueryInfo, qs: qsClient.QueryServerClient): void {
-    queryInfo.evalLogLocation = this.evalLogPath;
-    void qs.cliServer.generateLogSummary(this.evalLogPath, this.evalLogSummaryPath, this.evalLogEndSummaryPath)
-      .then(() => {
-        queryInfo.evalLogSummaryLocation = this.evalLogSummaryPath;
-        fs.readFile(this.evalLogEndSummaryPath, (err, buffer) => {
-          if (err) {
-            throw new Error(`Could not read structured evaluator log end of summary file at ${this.evalLogEndSummaryPath}.`);
-          }
-          void qs.logger.log(' --- Evaluator Log Summary --- ', { additionalLogLocation: this.logPath });
-          void qs.logger.log(buffer.toString(), { additionalLogLocation: this.logPath });
-        });
-      })
-      .catch(err => {
-        void showAndLogWarningMessage(`Failed to generate human-readable structured evaluator log summary. Reason: ${err.message}`);
-      });
+  private async generateHumanReadableLogSummary(qs: qsClient.QueryServerClient): Promise<string | undefined> {
+    try {
+      await qs.cliServer.generateLogSummary(this.evalLogPath, this.evalLogSummaryPath, this.evalLogEndSummaryPath);
+      return this.evalLogSummaryPath;
+
+    } catch (e) {
+      const err = asError(e);
+      void showAndLogWarningMessage(`Failed to generate human-readable structured evaluator log summary. Reason: ${err.message}`);
+      return undefined;
+    }
+  }
+
+  /**
+   * Logs the end summary to the Output window and log file.
+   * @param logSummaryPath Path to the human-readable log summary
+   * @param qs The query server client.
+   */
+  private async logEndSummary(logSummaryPath: string | undefined, qs: qsClient.QueryServerClient): Promise<void> {
+    if (logSummaryPath === undefined) {
+      // Failed to generate the log, so we don't expect an end summary either.
+      return;
+    }
+
+    try {
+      const endSummaryContent = await fs.readFile(this.evalLogEndSummaryPath, 'utf-8');
+      void qs.logger.log(' --- Evaluator Log Summary --- ', { additionalLogLocation: this.logPath });
+      void qs.logger.log(endSummaryContent, { additionalLogLocation: this.logPath });
+    } catch (e) {
+      void showAndLogWarningMessage(`Could not read structured evaluator log end of summary file at ${this.evalLogEndSummaryPath}.`);
+    }
   }
 
   /**