Share generated interface member descriptors

README.md

@@ -171,10 +171,43 @@ For deployment, see
 | `--lang LANG` | No | `js` (default, emits `.js` + `.d.ts`) or `py` (emits `.py` + `.pyi` and `py.typed`) |
 | `--no-pyi` | No | With `--lang py`, emit implementation files without type stubs |
 | `--output DIR` | No | Output directory (default `./generated`) |
+| `--shared-interface-members` | No | JS opt-in: reuse shared required-interface prototype descriptors instead of duplicating inherited member bodies in every concrete class |
 | `--dry-run` | No | Validate input, don't write files |
 
 For each WinRT class the codegen emits a typed wrapper, factory, interface registration, async + progress support, generic collections, structs, enums, delegates, and an `index.js` / `index.d.ts` that re-exports every emitted symbol.
 
+### Shared interface members
+
+Large JavaScript projections can opt into shared inherited-interface
+implementations while preserving the public declaration API and import paths:
+
+```powershell
+dynwinrt-codegen generate `
+  --winmd-list .winapp\winmds.txt `
+  --class-name Microsoft.UI.Xaml.Controls.Button,Microsoft.UI.Xaml.Controls.TextBlock `
+  --output .winapp\bindings `
+  --shared-interface-members
+```
+
+The generated concrete prototypes receive the same method and accessor
+descriptors from standalone shared interface prototypes. Overloaded or
+conflicting members remain class-local, raw interface wrapper classes remain
+available, and the public declaration API and import paths are preserved. Class
+deep modules may replace inline required-interface declarations with equivalent
+re-exports from canonical standalone interface declarations. Only required
+interfaces already canonicalized as standalone shared wrappers participate;
+one-off inline required interfaces remain class-local. Generation without this
+flag remains byte-compatible with the default output. If a standalone
+interface filename is ambiguous between distinct interface identities, none of
+those identities participate in sharing and their inherited members remain
+class-local.
+
+Focused validation:
+
+```powershell
+cargo test -p dynwinrt-codegen --test shared_interface_members_test
+```
+
 ## Local development — fix import paths in generated files
 
 Generated files import from `'@microsoft/dynwinrt'`. When iterating against a locally-built runtime, rewrite imports to the relative path:

tools/dynwinrt-codegen/npm/README.md

@@ -56,8 +56,31 @@ npx dynwinrt-codegen generate \
 | `--ref PATH` | Additional `.winmd` files for type resolution only (no code emitted) |
 | `--lang LANG` | `js` (default, emits `.js` + `.d.ts`) or `py` (Python) |
 | `--output DIR` | Output directory (default `./generated`) |
+| `--shared-interface-members` | JS opt-in that shares inherited interface member descriptors across concrete classes |
 | `--dry-run` | Validate input, don't write files |
 
+### Shared interface members
+
+```powershell
+npx dynwinrt-codegen generate `
+  --winmd-list .winapp\winmds.txt `
+  --class-name Microsoft.UI.Xaml.Controls.Button,Microsoft.UI.Xaml.Controls.TextBlock `
+  --output .winapp\bindings `
+  --shared-interface-members
+```
+
+The generated concrete prototypes reuse method and accessor descriptors from
+the standalone required-interface prototypes. Overloaded or conflicting
+members remain class-local, and raw interface wrappers remain available. The
+public declaration API and import paths are preserved. Class deep modules may
+replace inline required-interface declarations with equivalent re-exports from
+canonical standalone interface declarations. Only interfaces already emitted
+as canonical standalone shared wrappers participate; one-off inline required
+interfaces remain class-local. Generation without the flag remains
+byte-compatible with the default output. Generation excludes every identity
+behind a standalone interface filename that is ambiguous between distinct
+interface identities; those inherited members remain class-local.
+
 ## What gets generated
 
 For each WinRT class, the codegen emits:

tools/dynwinrt-codegen/src/codegen/winrt/javascript/ir.rs

@@ -213,6 +213,11 @@ pub struct ProjectedImport {
     pub is_runtime_package: bool,
 }
 
+pub struct ProjectedReExport {
+    pub name: String,
+    pub from: String,
+}
+
 /// Disposition of a required interface.
 pub enum RequiredIfaceDisposition {
     /// Imported from its own generated file
@@ -257,18 +262,43 @@ pub struct ProjectedClass {
     pub doc: Option<DocInfo>,
     pub members: Vec<ProjectedMember>,
     pub required_ifaces: Vec<ProjectedRequiredIface>,
+    /// Standalone shared sources imported by this class, including interfaces
+    /// whose descriptors remain class-local after conflict filtering.
+    pub shared_interface_sources: Vec<ProjectedSharedInterfaceSource>,
+    /// Required-interface members whose implementation descriptors are copied
+    /// from a shared standalone interface prototype.
+    pub shared_interface_members: Vec<ProjectedSharedInterfaceMembers>,
     /// Static factory/static interface cache field declarations (JS only)
     pub static_cache_fields: Vec<String>,
     /// Static factory/static interface accessor methods (JS only)
     pub static_accessors: Vec<String>,
 }
 
+pub struct ProjectedSharedInterfaceSource {
+    pub interface_name: String,
+    pub interface_identity: String,
+}
+
+pub struct ProjectedSharedInterfaceMembers {
+    pub interface_name: String,
+    /// Normalized metadata identity expected from the standalone source file.
+    pub interface_identity: String,
+    /// Projection-level member keys used to suppress duplicate class bodies.
+    pub member_keys: Vec<String>,
+    /// JavaScript property-key expressions copied from the interface prototype.
+    pub descriptor_keys: Vec<String>,
+}
+
 pub struct ProjectedIface {
     pub name: String,
     pub doc: Option<DocInfo>,
     pub iid_const: Option<ProjectedIidConst>,
     pub has_static_from: bool,
     pub has_parameterized_cast: bool,
+    /// The interface prototype may be reused by concrete runtime classes.
+    pub shared_member_source: bool,
+    /// Normalized metadata identity stored on a shared member source.
+    pub interface_identity: String,
     pub members: Vec<ProjectedMember>,
     pub is_delegate: bool,
 }
@@ -295,6 +325,8 @@ pub struct ProjectedDelegate {
 pub struct ProjectedFile {
     pub name: String,
     pub imports: Vec<ProjectedImport>,
+    /// Public symbols preserved from a canonical sibling module.
+    pub re_exports: Vec<ProjectedReExport>,
     /// IID constants (rendered as `const` in JS, `declare const` in DTS)
     pub iid_consts: Vec<ProjectedIidConst>,
     /// Interface registration blocks (JS only)