From 943a475c3592149aad6062ad235338da548365ea Mon Sep 17 00:00:00 2001
From: fisker Cheung <lionkay@gmail.com>
Date: Thu, 9 Jul 2026 09:28:40 +0800
Subject: [PATCH] Angular: Support expression for exhaustive typechecking
 (#19571)

---
 changelog_unreleased/angular/19571.md         | 19 +++++++++++++
 package.json                                  |  2 +-
 .../print/angular-control-flow-block.js       | 18 ++++++++----
 .../__snapshots__/format.test.js.snap         | 28 +++++++++++++++++--
 .../angular/control-flow/default-never.html   | 16 +++++++++--
 yarn.lock                                     | 10 +++----
 6 files changed, 78 insertions(+), 15 deletions(-)
 create mode 100644 changelog_unreleased/angular/19571.md

diff --git a/changelog_unreleased/angular/19571.md b/changelog_unreleased/angular/19571.md
new file mode 100644
index 000000000..5ece540ab
--- /dev/null
+++ b/changelog_unreleased/angular/19571.md
@@ -0,0 +1,19 @@
+#### Support expression for exhaustive typechecking (#19571 by @fisker)
+
+<!-- prettier-ignore -->
+```html
+<!-- Input -->
+@switch (state.mode) {
+  @default never(state);
+}
+
+<!-- Prettier stable -->
+@switch (state.mode) {
+  @default never;
+}
+
+<!-- Prettier main -->
+@switch (state.mode) {
+  @default never(state);
+}
+```
diff --git a/package.json b/package.json
index bd98e6443..4855c43bd 100644
--- a/package.json
+++ b/package.json
@@ -58,7 +58,7 @@
     "acorn": "8.17.0",
     "acorn-jsx": "5.3.2",
     "angular-estree-parser": "15.5.0",
-    "angular-html-parser": "10.10.0",
+    "angular-html-parser": "10.11.0",
     "camelcase": "9.0.0",
     "ci-info": "4.4.0",
     "cjk-regex": "3.4.0",
diff --git a/src/language-html/print/angular-control-flow-block.js b/src/language-html/print/angular-control-flow-block.js
index 6281a5c1b..ab69b7ae5 100644
--- a/src/language-html/print/angular-control-flow-block.js
+++ b/src/language-html/print/angular-control-flow-block.js
@@ -20,13 +20,21 @@ function printAngularControlFlowBlock(path, options, print) {
 
   docs.push("@", node.name);
 
-  if (isSwitchExhaustiveCheck(node)) {
-    docs.push(";");
-    return docs;
-  }
+  const isDefaultNever = isSwitchExhaustiveCheck(node);
 
   if (node.parameters) {
-    docs.push(" ", "(", group(print("parameters")), ")");
+    // No space in `@default never(state)`
+    // https://github.com/prettier/prettier/issues/19570#issuecomment-4916194365
+    if (!isDefaultNever) {
+      docs.push(" ");
+    }
+
+    docs.push("(", group(print("parameters")), ")");
+  }
+
+  if (isDefaultNever) {
+    docs.push(";");
+    return docs;
   }
 
   if (!isSwitchFallthroughCase(node)) {
diff --git a/tests/format/angular/control-flow/__snapshots__/format.test.js.snap b/tests/format/angular/control-flow/__snapshots__/format.test.js.snap
index deac6b286..8cf72183e 100644
--- a/tests/format/angular/control-flow/__snapshots__/format.test.js.snap
+++ b/tests/format/angular/control-flow/__snapshots__/format.test.js.snap
@@ -161,8 +161,20 @@ parsers: ["angular"]
   @default never;
 }
 
-@switch (   cond.kind) {
-  @default never    ;
+@switch (   cond.kind      ) {
+      @default      never      ;
+}
+
+@switch (   state.mode) {
+   @default never(state);
+}
+
+@switch (      state.mode      ) {
+      @default      never      (      state      )      ;
+}
+
+@switch (   expr) {
+   @default never(expr.prop);
 }
 
 =====================================output=====================================
@@ -174,6 +186,18 @@ parsers: ["angular"]
   @default never;
 }
 
+@switch (state.mode) {
+  @default never(state);
+}
+
+@switch (state.mode) {
+  @default never(state);
+}
+
+@switch (expr) {
+  @default never(expr.prop);
+}
+
 ================================================================================
 `;
 
diff --git a/tests/format/angular/control-flow/default-never.html b/tests/format/angular/control-flow/default-never.html
index 9f954fd91..5beac259b 100644
--- a/tests/format/angular/control-flow/default-never.html
+++ b/tests/format/angular/control-flow/default-never.html
@@ -2,6 +2,18 @@
   @default never;
 }
 
-@switch (   cond.kind) {
-  @default never    ;
+@switch (   cond.kind      ) {
+      @default      never      ;
+}
+
+@switch (   state.mode) {
+   @default never(state);
+}
+
+@switch (      state.mode      ) {
+      @default      never      (      state      )      ;
+}
+
+@switch (   expr) {
+   @default never(expr.prop);
 }
diff --git a/yarn.lock b/yarn.lock
index 01c7198dd..5cb2c0ab4 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3088,10 +3088,10 @@ __metadata:
   languageName: node
   linkType: hard
 
-"angular-html-parser@npm:10.10.0":
-  version: 10.10.0
-  resolution: "angular-html-parser@npm:10.10.0"
-  checksum: 10/820a1e96439d1ab02d4fb3524ac6a09a2b9a8622879692732508ee96c6f9847fdd899a3750714e6e39aff06ec864c405c5555167ed8068fd1e613b0f151c633f
+"angular-html-parser@npm:10.11.0":
+  version: 10.11.0
+  resolution: "angular-html-parser@npm:10.11.0"
+  checksum: 10/b311b3e984eaba422d41ecff8ea1255c1e5d5cd86ffd88f8651b12323b33104a0099711e1f4104dfe4f4383ff926ac43df4f072bf616f5dbbc5e86ef76e33383
   languageName: node
   linkType: hard
 
@@ -8212,7 +8212,7 @@ __metadata:
     acorn: "npm:8.17.0"
     acorn-jsx: "npm:5.3.2"
     angular-estree-parser: "npm:15.5.0"
-    angular-html-parser: "npm:10.10.0"
+    angular-html-parser: "npm:10.11.0"
     base64-arraybuffer-es6: "npm:3.1.0"
     browserslist: "npm:4.28.5"
     browserslist-to-esbuild: "npm:2.1.1"