From 79b7438defe33ea42e143b8f8532e18d336bae96 Mon Sep 17 00:00:00 2001
From: Damian Kaczmarek <rush@rushbase.net>
Date: Wed, 21 Oct 2026 12:55:54 -0500
Subject: [PATCH] fix(lexer): a `<` doesn't end a @let value

`@let small = count < 10;` was cut at the `<`, which the lexer took for a tag,
and reported as an incomplete @let declaration, so the component wasn't
compiled. Like Angular's `_consumeLetDeclarationValue`, only a `;` outside
quotes (or EOF) ends the value now.
---
 .../src/parser/html/lexer.rs                  |  5 +--
 .../tests/html_lexer_test.rs                  | 30 +++++++++++++++++
 .../tests/let_value_less_than_test.rs         | 32 +++++++++++++++++++
 3 files changed, 65 insertions(+), 2 deletions(-)
 create mode 100644 crates/oxc_angular_compiler/tests/let_value_less_than_test.rs

diff --git a/crates/oxc_angular_compiler/src/parser/html/lexer.rs b/crates/oxc_angular_compiler/src/parser/html/lexer.rs
index 2b03220dd..059d82b6f 100644
--- a/crates/oxc_angular_compiler/src/parser/html/lexer.rs
+++ b/crates/oxc_angular_compiler/src/parser/html/lexer.rs
@@ -1360,8 +1360,9 @@ impl<'a> HtmlLexer<'a> {
                 break;
             }
 
-            // EOF or tag start ends the value
-            if ch == chars::EOF || ch == '<' {
+            // EOF ends the value. A `<` does not (`@let a = b < c;`): like Angular's
+            // `_consumeLetDeclarationValue`, only a semicolon outside quotes ends it.
+            if ch == chars::EOF {
                 break;
             }
 
diff --git a/crates/oxc_angular_compiler/tests/html_lexer_test.rs b/crates/oxc_angular_compiler/tests/html_lexer_test.rs
index 8a1202c16..b950f3ce6 100644
--- a/crates/oxc_angular_compiler/tests/html_lexer_test.rs
+++ b/crates/oxc_angular_compiler/tests/html_lexer_test.rs
@@ -1675,6 +1675,36 @@ mod let_declarations {
         );
     }
 
+    #[test]
+    fn should_parse_let_declaration_with_less_than_in_its_value() {
+        // Angular's `_consumeLetDeclarationValue` ends the value only at a `;`
+        // outside quotes (or EOF): a `<` is a comparison, not a tag
+        let result = tokenize_and_humanize_parts("@let small = count < 10;");
+        assert_eq!(
+            result,
+            vec![
+                (HtmlTokenType::LetStart, vec!["small".to_string()]),
+                (HtmlTokenType::LetValue, vec!["count < 10".to_string()]),
+                (HtmlTokenType::LetEnd, vec![]),
+                (HtmlTokenType::Eof, vec![]),
+            ]
+        );
+    }
+
+    #[test]
+    fn should_parse_let_declaration_with_comparisons_followed_by_an_element() {
+        let result = tokenize_and_humanize_parts("@let both = a < b && b < c;<span></span>");
+        assert_eq!(
+            result[..3],
+            [
+                (HtmlTokenType::LetStart, vec!["both".to_string()]),
+                (HtmlTokenType::LetValue, vec!["a < b && b < c".to_string()]),
+                (HtmlTokenType::LetEnd, vec![]),
+            ]
+        );
+        assert_eq!(result[3].0, HtmlTokenType::TagOpenStart);
+    }
+
     #[test]
     fn should_report_incomplete_let_without_equals_after_name() {
         // No upstream spec case; Angular's _consumeLetDeclaration marks the
diff --git a/crates/oxc_angular_compiler/tests/let_value_less_than_test.rs b/crates/oxc_angular_compiler/tests/let_value_less_than_test.rs
new file mode 100644
index 000000000..ca1b8f49a
--- /dev/null
+++ b/crates/oxc_angular_compiler/tests/let_value_less_than_test.rs
@@ -0,0 +1,32 @@
+//! A `@let` value can contain `<` (`@let small = count < 10;`): as in Angular's
+//! lexer, only a `;` outside quotes ends it. `@angular/compiler-cli` 21.0.1
+//! compiles the template below to `const small_r1 = ctx.count < 10;` and
+//! `const both_r2 = ctx.a < ctx.b && ctx.b < ctx.c;`.
+
+use oxc_allocator::Allocator;
+use oxc_angular_compiler::{TransformOptions, transform_angular_file};
+
+#[test]
+fn let_value_with_less_than_compiles_as_a_comparison() {
+    let source = r"
+import { Component } from '@angular/core';
+@Component({
+  selector: 'b-cmp',
+  template: `@let small = count < 10; @let both = a < b && b < c;
+<span>{{ small }} {{ both }}</span>`,
+})
+export class BCmp { count = 1; a = 1; b = 2; c = 3; }
+";
+    let allocator = Allocator::default();
+    let result = transform_angular_file(
+        &allocator,
+        "test.ts",
+        source,
+        Some(&TransformOptions::default()),
+        None,
+    );
+    assert!(!result.has_errors(), "Should not have errors: {:?}", result.diagnostics);
+    let code: String = result.code.chars().filter(|c| !c.is_whitespace()).collect();
+    assert!(code.contains("constsmall_r1=(ctx.count<10);"), "Got:\n{}", result.code);
+    assert!(code.contains("constboth_r2=((ctx.a<ctx.b)&&(ctx.b<ctx.c));"), "Got:\n{}", result.code);
+}