backend: Fetch package version at build time

Extract `fetch-version.ts` which is called at build time to create
file `dist/api/version.json`.
This file is read by `backend-info.ts` at runtime.

This also fixes handing over the Git commit hash to the backend app
in the Docker backend image, which was broken as of 2022-07-12.
(Reason: The commit hash was previously required at runtime, but was
only provided at build time.)

backend/package.json

@@ -22,7 +22,8 @@
   "main": "index.ts",
   "scripts": {
     "tsc": "./node_modules/typescript/bin/tsc -p tsconfig.build.json",
-    "build": "npm run tsc && cp ./src/tasks/price-feeds/mtgox-weekly.json ./dist/tasks/",
+    "build": "npm run tsc && npm run create-resources",
+    "create-resources": "cp ./src/tasks/price-feeds/mtgox-weekly.json ./dist/tasks && node dist/api/fetch-version.js",
     "start": "node --max-old-space-size=2048 dist/index.js",
     "start-production": "node --max-old-space-size=4096 dist/index.js",
     "test": "./node_modules/.bin/jest --coverage",

backend/src/api/backend-info.ts

@@ -1,60 +1,37 @@
-import * as fs from 'fs';
-import * as os from 'os';
-import logger from '../logger';
+import fs from 'fs';
+import path from 'path';
+import os from 'os';
 import { IBackendInfo } from '../mempool.interfaces';
-const { spawnSync } = require('child_process');
 
 class BackendInfo {
-  private gitCommitHash = '';
-  private hostname = '';
-  private version = '';
+  private backendInfo: IBackendInfo;
 
   constructor() {
-    this.setLatestCommitHash();
-    this.setVersion();
-    this.hostname = os.hostname();
-  }
-
-  public getBackendInfo(): IBackendInfo {
-    return {
-      hostname: this.hostname,
-      gitCommit: this.gitCommitHash,
-      version: this.version,
+    // This file is created by ./fetch-version.ts during building
+    const versionFile = path.join(__dirname, 'version.json')
+    var versionInfo;
+    if (fs.existsSync(versionFile)) {
+      versionInfo = JSON.parse(fs.readFileSync(versionFile).toString());
+    } else {
+      // Use dummy values if `versionFile` doesn't exist (e.g., during testing)
+      versionInfo = {
+        version: '?',
+        gitCommit: '?'
+      };
+    }
+    this.backendInfo = {
+      hostname: os.hostname(),
+      version: versionInfo.version,
+      gitCommit: versionInfo.gitCommit
     };
   }
 
+  public getBackendInfo(): IBackendInfo {
+    return this.backendInfo;
+  }
+
   public getShortCommitHash() {
-    return this.gitCommitHash.slice(0, 7);
-  }
-
-  private setLatestCommitHash(): void {
-    //TODO: share this logic with `generate-config.js`
-    if (process.env.DOCKER_COMMIT_HASH) {
-      this.gitCommitHash = process.env.DOCKER_COMMIT_HASH;
-    } else {
-      try {
-        const gitRevParse = spawnSync('git', ['rev-parse', '--short', 'HEAD']);
-        if (!gitRevParse.error) {
-          const output = gitRevParse.stdout.toString('utf-8').replace(/[\n\r\s]+$/, '');
-          this.gitCommitHash = output ? output : '?';
-        } else if (gitRevParse.error.code === 'ENOENT') {
-          console.log('git not found, cannot parse git hash');
-          this.gitCommitHash = '?';
-        }
-      } catch (e: any) {
-        console.log('Could not load git commit info: ' + e.message);
-        this.gitCommitHash = '?';
-      }
-    }
-  }
-
-  private setVersion(): void {
-    try {
-      const packageJson = fs.readFileSync('package.json').toString();
-      this.version = JSON.parse(packageJson).version;
-    } catch (e) {
-      throw new Error(e instanceof Error ? e.message : 'Error');
-    }
+    return this.backendInfo.gitCommit.slice(0, 7);
   }
 }
 

backend/src/api/fetch-version.ts

@@ -0,0 +1,37 @@
+import fs from 'fs';
+import path from "path";
+const { spawnSync } = require('child_process');
+
+function getVersion(): string {
+  const packageJson = fs.readFileSync('package.json').toString();
+  return JSON.parse(packageJson).version;
+}
+
+function getGitCommit(): string {
+  if (process.env.DOCKER_COMMIT_HASH) {
+    return process.env.DOCKER_COMMIT_HASH;
+  } else {
+    const gitRevParse = spawnSync('git', ['rev-parse', '--short', 'HEAD']);
+    if (!gitRevParse.error) {
+      const output = gitRevParse.stdout.toString('utf-8').replace(/[\n\r\s]+$/, '');
+      if (output) {
+        return output;
+      } else {
+        console.log('Could not fetch git commit: No repo available');
+      }
+    } else if (gitRevParse.error.code === 'ENOENT') {
+      console.log('Could not fetch git commit: Command `git` is unavailable');
+    }
+  }
+  return '?';
+}
+
+const versionInfo = {
+  version: getVersion(),
+  gitCommit: getGitCommit()
+}
+
+fs.writeFileSync(
+  path.join(__dirname, 'version.json'),
+  JSON.stringify(versionInfo, null, 2) + "\n"
+);