From a1b5e84044f316992465c3d4ed99466a987355e0 Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Mon, 4 Dec 2023 12:07:07 -0500
Subject: [PATCH] refactor(compiler): provide a private API to perform direct
 style encapsulation
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To support the development of component specific HMR capabilities, the build/serve
tooling may need to directly process styles to match the view encapsulation
expectations of individual components. To allow for this scenario and to avoid tooling
to need to re-implement the emulated encapsulation logic, an private API is now
available in the `@angular/compiler` package named `ɵencapsulateStyle` that converts
a stylesheet content string to an encapsulated form. This function is prefixed with
the private symbol and is not considered part of the public API nor does it have
any of its respective support or versioning guarantees.
---
 packages/compiler/src/compiler.ts              |  2 +-
 packages/compiler/src/render3/view/compiler.ts | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/packages/compiler/src/compiler.ts b/packages/compiler/src/compiler.ts
index 215edcfec02035..3d46a8d8163a1a 100644
--- a/packages/compiler/src/compiler.ts
+++ b/packages/compiler/src/compiler.ts
@@ -76,7 +76,7 @@ export {compileInjector, R3InjectorMetadata} from './render3/r3_injector_compile
 export {compilePipeFromMetadata, R3PipeMetadata} from './render3/r3_pipe_compiler';
 export {makeBindingParser, ParsedTemplate, parseTemplate, ParseTemplateOptions} from './render3/view/template';
 export {ForwardRefHandling, MaybeForwardRefExpression, R3CompiledExpression, R3Reference, createMayBeForwardRefExpression, devOnlyGuardedExpression, getSafePropertyAccessString} from './render3/util';
-export {compileComponentFromMetadata, compileDirectiveFromMetadata, parseHostBindings, ParsedHostBindings, verifyHostBindings} from './render3/view/compiler';
+export {compileComponentFromMetadata, compileDirectiveFromMetadata, parseHostBindings, ParsedHostBindings, verifyHostBindings, encapsulateStyle as ɵencapsulateStyle} from './render3/view/compiler';
 export {compileDeclareClassMetadata} from './render3/partial/class_metadata';
 export {compileDeclareComponentFromMetadata, DeclareComponentTemplateInfo} from './render3/partial/component';
 export {compileDeclareDirectiveFromMetadata} from './render3/partial/directive';
diff --git a/packages/compiler/src/render3/view/compiler.ts b/packages/compiler/src/render3/view/compiler.ts
index 2eebafee76897f..395ea80d491a8f 100644
--- a/packages/compiler/src/render3/view/compiler.ts
+++ b/packages/compiler/src/render3/view/compiler.ts
@@ -981,6 +981,19 @@ function compileStyles(styles: string[], selector: string, hostSelector: string)
   });
 }
 
+/**
+ * Encapsulates a CSS stylesheet with emulated view encapsulation.
+ * This allows a stylesheet to be used with an Angular component that
+ * is using the `ViewEncapsulation.Emulated` mode.
+ *
+ * @param style The content of a CSS stylesheet.
+ * @returns The encapsulated content for the style.
+ */
+export function encapsulateStyle(style: string): string {
+  const shadowCss = new ShadowCss();
+  return shadowCss.shimCssText(style, CONTENT_ATTR, HOST_ATTR);
+}
+
 function createHostDirectivesType(meta: R3DirectiveMetadata): o.Type {
   if (!meta.hostDirectives?.length) {
     return o.NONE_TYPE;