feat(@angular/build): support custom resolution conditions with applications

When using the application build system, a new `conditions` option is now
available that allows adding custom package resolution conditions that
can adjust the resolution for conditional exports and imports.
By default the `module` and `production`/`development` conditions will be
present with the later dependent on the `optimization` option. If any
custom conditions value is present including an empty array, none of these
defaults will be present and must be manually included if needed.
The following special conditions will always be present if their respective
requirements are satisfied:
* es2015 (required by rxjs)
* es2020 (APF backwards compatibility)
* default
* import
* require
* node
* browser

For additional information regarding conditional exports/imports:
https://nodejs.org/api/packages.html#conditional-exports
https://nodejs.org/api/packages.html#subpath-imports

Author: clydin

packages/angular/build/src/builders/application/options.ts

@@ -496,6 +496,7 @@ export async function normalizeOptions(
     security,
     templateUpdates: !!options.templateUpdates,
     incrementalResults: !!options.incrementalResults,
+    customConditions: options.conditions,
   };
 }
 

packages/angular/build/src/builders/application/schema.json

@@ -293,6 +293,13 @@
         "type": "string"
       }
     },
+    "conditions": {
+      "description": "Custom package resolution conditions used to resolve conditional exports/imports. Defaults to ['module', 'development'/'production']. The following special conditions are always present if the requirements are satisfied: 'default', 'import', 'require', 'browser', 'node'.",
+      "type": "array",
+      "items": {
+        "type": "string"
+      }
+    },
     "fileReplacements": {
       "description": "Replace compilation source files with other compilation source files in the build.",
       "type": "array",

packages/angular/build/src/tools/esbuild/application-code-bundle.ts

@@ -546,6 +546,7 @@ function getEsBuildCommonOptions(options: NormalizedApplicationBuildOptions): Bu
     loaderExtensions,
     jsonLogs,
     i18nOptions,
+    customConditions,
   } = options;
 
   // Ensure unique hashes for i18n translation changes when using post-process inlining.
@@ -563,18 +564,29 @@ function getEsBuildCommonOptions(options: NormalizedApplicationBuildOptions): Bu
     footer = { js: `/**i18n:${createHash('sha256').update(i18nHash).digest('hex')}*/` };
   }
 
+  // Core conditions that are always included
+  const conditions = [
+    // Required to support rxjs 7.x which will use es5 code if this condition is not present
+    'es2015',
+    'es2020',
+  ];
+
+  // Append custom conditions if present
+  if (customConditions) {
+    conditions.push(...customConditions);
+  } else {
+    // Include default conditions
+    conditions.push('module');
+    conditions.push(optimizationOptions.scripts ? 'production' : 'development');
+  }
+
   return {
     absWorkingDir: workspaceRoot,
     format: 'esm',
     bundle: true,
     packages: 'bundle',
     assetNames: outputNames.media,
-    conditions: [
-      'es2020',
-      'es2015',
-      'module',
-      optimizationOptions.scripts ? 'production' : 'development',
-    ],
+    conditions,
     resolveExtensions: ['.ts', '.tsx', '.mjs', '.js', '.cjs'],
     metafile: true,
     legalComments: options.extractLicenses ? 'none' : 'eof',