fix(hmr): write the new template's fields and stop redefining the live definition

crates/oxc_angular_compiler/src/component/transform.rs

@@ -418,6 +418,21 @@ pub struct HmrTemplateCompileOutput {
     /// constant references. Without this, the template may reference indices that don't
     /// exist in the old component definition's consts array.
     pub consts_js: Option<String>,
+
+    /// The number of element, text and container slots the template creates.
+    pub decls: u32,
+
+    /// The number of binding slots the template uses.
+    pub vars: u32,
+
+    /// The `ngContentSelectors` array as JavaScript code, when the template projects
+    /// content. It refers to a constant declared in `declarations_js`.
+    pub ng_content_selectors_js: Option<String>,
+
+    /// Non-fatal diagnostics the pipeline reported while compiling (warnings,
+    /// advice). Error-severity diagnostics are returned as `Err` instead, since
+    /// the emitted code cannot be trusted.
+    pub diagnostics: Vec<OxcDiagnostic>,
 }
 
 /// Compiled component information.
@@ -5490,11 +5505,14 @@ pub fn compile_template_for_hmr<'a>(
     // OXC is a single-file compiler (local compilation mode): always use Full mode.
     let mode = TemplateCompilationMode::Full;
 
-    let defer_block_deps_emit_mode = if options.jit {
-        DeferBlockDepsEmitMode::PerComponent
-    } else {
-        DeferBlockDepsEmitMode::PerBlock
-    };
+    // Defer-block dependency resolution needs component metadata this compile
+    // does not have, and PerBlock mode reports "unable to find a dependency
+    // function for this deferred block" for every `@defer` when its `blocks`
+    // map is not populated — nothing ever populates it here. Local compilation
+    // uses PerComponent (upstream handler.ts:1281); with no resolver available
+    // it still emits `ɵɵdefer` with a null dependencies argument, which is what
+    // PerBlock's empty map would have produced anyway.
+    let defer_block_deps_emit_mode = DeferBlockDepsEmitMode::PerComponent;
 
     let enable_debug_locations = !options.advanced_optimizations;
 
@@ -5526,6 +5544,15 @@ pub fn compile_template_for_hmr<'a>(
     // Collect any diagnostics from the compilation job
     diagnostics.extend(job.diagnostics.into_iter());
 
+    // A pipeline error means the emitted code is already wrong — an update
+    // module must not be generated from it, and `decls`/`vars` may not be
+    // reliable (they default to 0 when slot allocation never ran, which would
+    // size the new TView incorrectly). Non-error diagnostics go out on the
+    // output so the caller can surface them.
+    if diagnostics.iter().any(|d| d.severity == oxc_diagnostics::Severity::Error) {
+        return Err(diagnostics);
+    }
+
     let emitter = JsEmitter::new();
 
     // Emit the template function
@@ -5604,7 +5631,19 @@ pub fn compile_template_for_hmr<'a>(
         None
     };
 
-    Ok(HmrTemplateCompileOutput { template_js, declarations_js, styles, consts_js })
+    let ng_content_selectors_js =
+        job.content_selectors.take().map(|selectors| emitter.emit_expression(&selectors));
+
+    Ok(HmrTemplateCompileOutput {
+        template_js,
+        declarations_js,
+        styles,
+        consts_js,
+        decls: job.root.decl_count.unwrap_or(0),
+        vars: job.root.vars.unwrap_or(0),
+        ng_content_selectors_js,
+        diagnostics,
+    })
 }
 
 /// Generate component compilation output for HMR.

crates/oxc_angular_compiler/src/hmr/mod.rs

@@ -27,10 +27,18 @@
 //! });
 //!
 //! // HMR Update Module (served by Vite middleware)
-//! export default {
-//!   ɵcmp: /* compiled component definition */,
-//!   template: /* template function */,
-//! };
+//! export default function Cmp_UpdateMetadata(Cmp, ɵɵnamespaces) {
+//!   const i0 = ɵɵnamespaces[0];
+//!   Cmp.ɵcmp = {
+//!     ...Cmp.ɵcmp,
+//!     decls: /* new template's slot count */,
+//!     vars: /* new template's binding count */,
+//!     consts: /* new template's consts, or null */,
+//!     ngContentSelectors: /* new template's selectors, or undefined */,
+//!     template: /* new template function */,
+//!     tView: null,
+//!   };
+//! }
 //! ```
 
 mod dependencies;
@@ -46,5 +54,6 @@ pub use dependencies::{
 pub use initializer::{HmrDefinition, compile_hmr_initializer, compile_hmr_update_callback};
 pub use styles::generate_style_update_module;
 pub use update_module::{
-    HmrUpdateModuleOptions, generate_hmr_update_module, generate_hmr_update_module_from_js,
+    HmrTemplateFields, HmrUpdateModuleOptions, generate_hmr_update_module,
+    generate_hmr_update_module_from_js,
 };