Changed location of built public content to temporary dir (#21857)

refs
[ONC-662](https://linear.app/ghost/issue/ONC-662/fix-file-write-issues-in-ghost-application-related-to-asset-generation)

Changed location of built public content to temporary dir to circumvent
file writing issues in some environments (i.e gluster). This is a
stop-gap measure until we get to refactoring the generation of the built
public content.

ghost/core/core/shared/config/helpers.js

@@ -1,3 +1,5 @@
+const crypto = require('crypto');
+const os = require('os');
 const path = require('path');
 const {URL} = require('url');
 
@@ -64,6 +66,24 @@ const isPrivacyDisabled = function isPrivacyDisabled(privacyFlag) {
     return this.get('privacy')[privacyFlag] === false;
 };
 
+/** @type {string|null} */
+let processTmpDirPath = null;
+
+/**
+ * Get a tmp dir path for the current process
+ *
+ * @returns {string} - tmp dir path for the current process
+ */
+function getProcessTmpDirPath() {
+    // Memoize the computed path to avoid re-computing it on each call - The
+    // value should not change during the lifetime of the process.
+    if (processTmpDirPath === null) {
+        processTmpDirPath = path.join(os.tmpdir(), `ghost_${crypto.randomUUID()}`);
+    }
+
+    return processTmpDirPath;
+}
+
 /**
  * @callback getContentPathFn
  * @param {string} type - the type of context you want the path for
@@ -88,7 +108,7 @@ const getContentPath = function getContentPath(type) {
     case 'settings':
         return path.join(this.get('paths:contentPath'), 'settings/');
     case 'public':
-        return path.join(this.get('paths:contentPath'), 'public/');
+        return path.join(getProcessTmpDirPath(this), 'public/');
     default:
         // new Error is allowed here, as we do not want config to depend on @tryghost/error
         // @TODO: revisit this decision when @tryghost/error is no longer dependent on all of ghost-ignition

ghost/core/test/unit/frontend/web/middleware/serve-public-file.test.js

@@ -187,6 +187,6 @@ describe('servePublicFile', function () {
         res.writeHead.called.should.be.true();
         res.writeHead.args[0][0].should.equal(200);
 
-        fileStub.firstCall.args[0].should.endWith('content/public/something.css');
+        fileStub.firstCall.args[0].should.endWith('/public/something.css');
     });
 });

ghost/core/test/unit/shared/config/helpers.test.js

@@ -1,6 +1,10 @@
+const os = require('os');
 const should = require('should');
+
 const configUtils = require('../../../utils/configUtils');
 
+const UUID_REGEX = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/;
+
 describe('vhost utils', function () {
     beforeEach(function () {
         configUtils.set('url', 'http://ghost.blog');
@@ -52,3 +56,29 @@ describe('vhost utils', function () {
         });
     });
 });
+
+describe('getContentPath', function () {
+    it('should return the correct path for type: public', function () {
+        const publicPath = configUtils.config.getContentPath('public');
+
+        // Path should be in the tmpdir
+        const tmpdir = os.tmpdir();
+
+        publicPath.startsWith(tmpdir).should.be.true();
+
+        // Path should end with /public/
+        publicPath.endsWith('/public/').should.be.true();
+
+        // Path should include /ghost_
+        publicPath.includes('/ghost_').should.be.true();
+
+        // Path should contain a uuid at the correct location
+        const publicPathParts = publicPath.split('/');
+        const uuidPart = publicPathParts[publicPathParts.length - 3].replace('ghost_', '');
+
+        UUID_REGEX.test(uuidPart).should.be.true();
+
+        // Path should be memoized
+        configUtils.config.getContentPath('public').should.eql(publicPath);
+    });
+});