From 91b93d852d04ca01488572903826a2793cc06b8a Mon Sep 17 00:00:00 2001
From: "Houston (Jeb's AI)" <houston@base44.com>
Date: Mon, 27 Apr 2026 06:49:55 +0000
Subject: [PATCH 1/2] fix(jest): default isolatedModules to true for faster
 compilation (fixes #1899)
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Angular 19 introduced signals, new control flow syntax, and standalone-by-default
components. These produce significantly more complex TypeScript that causes the
ts-jest language service (used when isolatedModules: false) to build a full
cross-file Program per test file, resulting in severe slowdowns (reports of
2 min → 15 min test runs).

Root cause: when isolatedModules is false (previously the implicit default),
ts-jest instantiates a TypeScript LanguageService and rebuilds a full Program
for each file. Angular 19+'s richer type surface makes this path prohibitively
slow.

Fix: set isolatedModules: true in the builder's default transformer options.
This switches ts-jest to its fast per-file transpile path, matching the
recommendation from jest-preset-angular's own example apps since v14.4.0.

Cross-file type checking is better served by tsc --noEmit or ng build.
Users who need the previous behaviour can opt out in their jest.config.ts:

  transform: {
    '^.+\.(ts|js|mjs|html|svg)$': ['jest-preset-angular', { isolatedModules: false }]
  }

BREAKING CHANGE: isolatedModules now defaults to true. This disables
cross-file TypeScript type checking during jest runs. Targeted for the
next major version.
---
 packages/jest/src/default-config.resolver.spec.ts |  2 ++
 packages/jest/src/default-config.resolver.ts      | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/packages/jest/src/default-config.resolver.spec.ts b/packages/jest/src/default-config.resolver.spec.ts
index 2235f8f3db..26ff41ec69 100644
--- a/packages/jest/src/default-config.resolver.spec.ts
+++ b/packages/jest/src/default-config.resolver.spec.ts
@@ -14,6 +14,7 @@ describe('Resolve project default configuration', () => {
       {
         stringifyContentPathRegex: '\\.(html|svg)$',
         tsconfig: getSystemPath(normalize(`/some/cool/directory/${tsConfigName}`)),
+        isolatedModules: true,
       },
     ]);
   });
@@ -28,6 +29,7 @@ describe('Resolve project default configuration', () => {
       {
         stringifyContentPathRegex: '\\.(html|svg)$',
         tsconfig: getSystemPath(normalize(`/some/cool/project/ts-configs/tsconfig.spec.json`)),
+        isolatedModules: true,
       },
     ]);
   });
diff --git a/packages/jest/src/default-config.resolver.ts b/packages/jest/src/default-config.resolver.ts
index f9d950c19e..022bce8234 100644
--- a/packages/jest/src/default-config.resolver.ts
+++ b/packages/jest/src/default-config.resolver.ts
@@ -47,6 +47,16 @@ export class DefaultConfigResolver {
             stringifyContentPathRegex: '\\.(html|svg)$',
             // Join with the default `tsConfigName` if the `tsConfig` option is not provided
             tsconfig: getTsConfigPath(projectRoot, this.options),
+            // Default to isolatedModules: true for significantly faster compilation.
+            // With isolatedModules: false (the previous implicit default), ts-jest uses the
+            // TypeScript language service to build a full cross-file Program for every test
+            // file, which becomes extremely slow with Angular 19+ code (signals, new control
+            // flow, standalone-by-default). Angular 19+ users report 2min → 15min regressions.
+            // Cross-file type checking is better handled by `tsc --noEmit` or `ng build`.
+            // Users who need the old behaviour can opt out via their jest.config.ts:
+            //   transform: { '...': ['jest-preset-angular', { isolatedModules: false }] }
+            // BREAKING CHANGE: targeted for the next major version.
+            isolatedModules: true,
           },
         ],
       },

From 977cbb1596038decf30975dd16f181005fc5ec3e Mon Sep 17 00:00:00 2001
From: "Houston (Jeb's AI)" <houston@base44.com>
Date: Mon, 27 Apr 2026 08:08:45 +0000
Subject: [PATCH 2/2] docs(custom-esbuild): document target.configuration in
 plugin and indexHtmlTransformer (fixes #1899)

- Add target.configuration to factory plugin example in README (alongside existing target.project)
- Update indexHtmlTransformer examples (JS and TS) to include the target param with comments
- Add integration test 'target-options-in-plugin-and-transformer' that builds with a real
  factory plugin and indexHtmlTransformer, both using target.configuration, then verifies
  the value appears in the JS bundle and index.html meta tag
- Add esbuild/define-configuration-plugin.js and esbuild/configuration-transformer.js
  to sanity-esbuild-app as the test fixtures
---
 .../sanity-esbuild-app/angular.json           | 10 ++++++++-
 .../esbuild/configuration-transformer.js      | 10 +++++++++
 .../esbuild/define-configuration-plugin.js    | 21 +++++++++++++++++++
 .../sanity-esbuild-app/package.json           |  5 +++--
 .../src/app/app.component.html                |  1 +
 .../src/app/app.component.ts                  |  3 +++
 packages/custom-esbuild/README.md             | 13 ++++++++++--
 packages/custom-esbuild/tests/integration.js  | 10 +++++++++
 8 files changed, 68 insertions(+), 5 deletions(-)
 create mode 100644 examples/custom-esbuild/sanity-esbuild-app/esbuild/configuration-transformer.js
 create mode 100644 examples/custom-esbuild/sanity-esbuild-app/esbuild/define-configuration-plugin.js

diff --git a/examples/custom-esbuild/sanity-esbuild-app/angular.json b/examples/custom-esbuild/sanity-esbuild-app/angular.json
index bf46ee4396..068af97671 100644
--- a/examples/custom-esbuild/sanity-esbuild-app/angular.json
+++ b/examples/custom-esbuild/sanity-esbuild-app/angular.json
@@ -80,6 +80,14 @@
                   }
                 }
               ]
+            },
+            "target-options-test": {
+              "plugins": [
+                "esbuild/define-configuration-plugin.js"
+              ],
+              "indexHtmlTransformer": "esbuild/configuration-transformer.js",
+              "optimization": false,
+              "outputHashing": "none"
             }
           },
           "defaultConfiguration": "production"
@@ -206,4 +214,4 @@
       "typeSeparator": "."
     }
   }
-}
+}
\ No newline at end of file
diff --git a/examples/custom-esbuild/sanity-esbuild-app/esbuild/configuration-transformer.js b/examples/custom-esbuild/sanity-esbuild-app/esbuild/configuration-transformer.js
new file mode 100644
index 0000000000..63bb308295
--- /dev/null
+++ b/examples/custom-esbuild/sanity-esbuild-app/esbuild/configuration-transformer.js
@@ -0,0 +1,10 @@
+/**
+ * Index HTML transformer for issues #1690 / #1710 test.
+ * Signature: (indexHtml: string, target: Target) => string
+ * Injects a <meta> tag with the configuration name so we can verify it in the output file.
+ */
+module.exports = function configurationTransformer(indexHtml, target) {
+  const configuration = target.configuration ?? 'default';
+  const metaTag = `<meta name="build-configuration" content="${configuration}">`;
+  return indexHtml.replace('</head>', `  ${metaTag}\n</head>`);
+};
diff --git a/examples/custom-esbuild/sanity-esbuild-app/esbuild/define-configuration-plugin.js b/examples/custom-esbuild/sanity-esbuild-app/esbuild/define-configuration-plugin.js
new file mode 100644
index 0000000000..8a5bb7e45a
--- /dev/null
+++ b/examples/custom-esbuild/sanity-esbuild-app/esbuild/define-configuration-plugin.js
@@ -0,0 +1,21 @@
+/**
+ * Factory plugin (Pattern 1: string path in angular.json).
+ * Receives (builderOptions, target) from the builder.
+ * Injects `target.configuration` as a global define constant `buildConfiguration`.
+ *
+ * This is the test for issues #1710 and #1690:
+ * verifying that target.configuration is accessible inside a factory plugin.
+ */
+function defineConfigurationPlugin(builderOptions, target) {
+  const configuration = target.configuration ?? 'default';
+  return {
+    name: 'define-configuration',
+    setup(build) {
+      const options = build.initialOptions;
+      options.define = options.define || {};
+      options.define.buildConfiguration = JSON.stringify(configuration);
+    },
+  };
+}
+
+module.exports = defineConfigurationPlugin;
diff --git a/examples/custom-esbuild/sanity-esbuild-app/package.json b/examples/custom-esbuild/sanity-esbuild-app/package.json
index fd76748c4a..ff4c824081 100644
--- a/examples/custom-esbuild/sanity-esbuild-app/package.json
+++ b/examples/custom-esbuild/sanity-esbuild-app/package.json
@@ -8,7 +8,8 @@
     "lint": "ng lint",
     "e2e": "ng e2e",
     "cypress:open": "cypress open",
-    "cypress:run": "cypress run"
+    "cypress:run": "cypress run",
+    "build-target-options": "ng build --configuration target-options-test && node -e \"const fs = require('fs');const dist = 'dist/sanity-esbuild-app/browser';const indexHtml = fs.readFileSync(dist + '/index.html', 'utf8');const jsFiles = fs.readdirSync(dist).filter(f => f.endsWith('.js'));const mainJs = jsFiles.map(f => fs.readFileSync(dist + '/' + f, 'utf8')).join('');if (!indexHtml.includes('content=\\\"target-options-test\\\"')) { console.error('FAIL: indexHtmlTransformer did not inject configuration into index.html'); process.exit(1); }if (!mainJs.includes('target-options-test')) { console.error('FAIL: plugin did not inject buildConfiguration into JS bundle'); process.exit(1); }console.log('PASS: target.configuration is accessible in both plugin and indexHtmlTransformer');\""
   },
   "private": true,
   "dependencies": {
@@ -42,4 +43,4 @@
     "typescript-eslint": "8.59.0",
     "vitest": "4.1.5"
   }
-}
+}
\ No newline at end of file
diff --git a/examples/custom-esbuild/sanity-esbuild-app/src/app/app.component.html b/examples/custom-esbuild/sanity-esbuild-app/src/app/app.component.html
index 7034c8f302..7e7a14d708 100644
--- a/examples/custom-esbuild/sanity-esbuild-app/src/app/app.component.html
+++ b/examples/custom-esbuild/sanity-esbuild-app/src/app/app.component.html
@@ -1,3 +1,4 @@
 <h1>{{ title }}</h1>
 <h2>{{ subtitle }}</h2>
 <h3>{{ titleByOption }}</h3>
+<p id="build-configuration">{{ buildConfiguration }}</p>
diff --git a/examples/custom-esbuild/sanity-esbuild-app/src/app/app.component.ts b/examples/custom-esbuild/sanity-esbuild-app/src/app/app.component.ts
index b878467344..ca0d751028 100644
--- a/examples/custom-esbuild/sanity-esbuild-app/src/app/app.component.ts
+++ b/examples/custom-esbuild/sanity-esbuild-app/src/app/app.component.ts
@@ -3,6 +3,7 @@ import { Component } from '@angular/core';
 declare const title: string;
 declare const subtitle: string;
 declare const titleByOption: string;
+declare const buildConfiguration: string;
 
 @Component({
   selector: 'app-root',
@@ -14,10 +15,12 @@ export class AppComponent {
   title: string;
   subtitle: string;
   titleByOption: string;
+  buildConfiguration: string;
 
   constructor() {
     this.title = typeof title !== 'undefined' ? title : 'sanity-esbuild-app';
     this.subtitle = typeof subtitle !== 'undefined' ? subtitle : 'sanity-esbuild-app subtitle';
     this.titleByOption = typeof titleByOption !== 'undefined' ? titleByOption : 'sanity-esbuild-app optionTitle';
+    this.buildConfiguration = typeof buildConfiguration !== 'undefined' ? buildConfiguration : 'no-config';
   }
 }
diff --git a/packages/custom-esbuild/README.md b/packages/custom-esbuild/README.md
index 7fcaf14728..931877908c 100644
--- a/packages/custom-esbuild/README.md
+++ b/packages/custom-esbuild/README.md
@@ -202,7 +202,10 @@ export default (builderOptions: ApplicationBuilderOptions, target: Target): Plug
     name: 'define-text',
     setup(build: PluginBuild) {
       const options = build.initialOptions;
+      // target.project is the Angular project name (e.g. "my-app")
       options.define.currentProject = JSON.stringify(target.project);
+      // target.configuration is the active build configuration (e.g. "production", "staging")
+      options.define.currentConfiguration = JSON.stringify(target.configuration ?? 'default');
     },
   };
 };
@@ -296,7 +299,9 @@ It is useful when you want to transform your `index.html` according to the build
 `index-html-transformer.js`:
 
 ```js
-module.exports = indexHtml => {
+module.exports = (indexHtml, target) => {
+  // target.configuration is the active build configuration (e.g. "production", "staging")
+  // target.project is the Angular project name
   const i = indexHtml.indexOf('</body>');
   const content = `<p>Dynamically inserted content</p>`;
   return `${indexHtml.slice(0, i)}
@@ -308,7 +313,11 @@ module.exports = indexHtml => {
 Alternatively, using TypeScript:
 
 ```ts
-export default (indexHtml: string) => {
+import type { Target } from '@angular-devkit/architect';
+
+export default (indexHtml: string, target: Target) => {
+  // target.configuration is the active build configuration (e.g. "production", "staging")
+  // target.project is the Angular project name
   const i = indexHtml.indexOf('</body>');
   const content = `<p>Dynamically inserted content</p>`;
   return `${indexHtml.slice(0, i)}
diff --git a/packages/custom-esbuild/tests/integration.js b/packages/custom-esbuild/tests/integration.js
index 4932b6ed73..ea0acdbce3 100644
--- a/packages/custom-esbuild/tests/integration.js
+++ b/packages/custom-esbuild/tests/integration.js
@@ -88,4 +88,14 @@ module.exports = [
     app: 'examples/custom-esbuild/sanity-esbuild-app-esm',
     command: 'yarn build-ts -c tsEsm',
   },
+
+  // Target options accessibility (#1690, #1710)
+  {
+    id: 'target-options-in-plugin-and-transformer',
+    name: 'custom-esbuild: target.configuration accessible in plugin and indexHtmlTransformer',
+    purpose:
+      'Factory plugin and indexHtmlTransformer both receive target.configuration at runtime',
+    app: 'examples/custom-esbuild/sanity-esbuild-app',
+    command: 'yarn build-target-options',
+  },
 ];