From cb8cdadd3bb4dc99eedc8453fcc573ee48b3258b Mon Sep 17 00:00:00 2001
From: Kristiyan Kostadinov <crisbeto@abv.bg>
Date: Fri, 28 Apr 2023 13:20:56 +0200
Subject: [PATCH] refactor(compiler): reflect arrow function definition
 (#50084)

Adds some logic to reflect an arrow function to `ReflectionHost.getDefinitionOfFunction`. This will be useful for some upcoming work.

PR Close #50084
---
 .../src/ngtsc/reflection/src/host.ts             | 13 ++++++++++++-
 .../src/ngtsc/reflection/src/typescript.ts       | 16 +++++++++++++---
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/packages/compiler-cli/src/ngtsc/reflection/src/host.ts b/packages/compiler-cli/src/ngtsc/reflection/src/host.ts
index ded55cf0c98..9833af3a0fa 100644
--- a/packages/compiler-cli/src/ngtsc/reflection/src/host.ts
+++ b/packages/compiler-cli/src/ngtsc/reflection/src/host.ts
@@ -396,7 +396,8 @@ export interface FunctionDefinition {
   /**
    * A reference to the node which declares the function.
    */
-  node: ts.MethodDeclaration|ts.FunctionDeclaration|ts.FunctionExpression|ts.VariableDeclaration;
+  node: ts.MethodDeclaration|ts.FunctionDeclaration|ts.FunctionExpression|ts.VariableDeclaration|
+      ts.ArrowFunction;
 
   /**
    * Statements of the function body, if a body is present, or null if no body is present or the
@@ -412,6 +413,11 @@ export interface FunctionDefinition {
    * Metadata regarding the function's parameters, including possible default value expressions.
    */
   parameters: Parameter[];
+
+  /**
+   * Generic type parameters of the function.
+   */
+  typeParameters: ts.TypeParameterDeclaration[]|null;
 }
 
 /**
@@ -432,6 +438,11 @@ export interface Parameter {
    * Expression which represents the default value of the parameter, if any.
    */
   initializer: ts.Expression|null;
+
+  /**
+   * Type of the parameter.
+   */
+  type: ts.TypeNode|null;
 }
 
 /**
diff --git a/packages/compiler-cli/src/ngtsc/reflection/src/typescript.ts b/packages/compiler-cli/src/ngtsc/reflection/src/typescript.ts
index d97dea268da..db44b341bad 100644
--- a/packages/compiler-cli/src/ngtsc/reflection/src/typescript.ts
+++ b/packages/compiler-cli/src/ngtsc/reflection/src/typescript.ts
@@ -164,16 +164,26 @@ export class TypeScriptReflectionHost implements ReflectionHost {
 
   getDefinitionOfFunction(node: ts.Node): FunctionDefinition|null {
     if (!ts.isFunctionDeclaration(node) && !ts.isMethodDeclaration(node) &&
-        !ts.isFunctionExpression(node)) {
+        !ts.isFunctionExpression(node) && !ts.isArrowFunction(node)) {
       return null;
     }
+
+    let body: ts.Statement[]|null = null;
+
+    if (node.body !== undefined) {
+      // The body might be an expression if the node is an arrow function.
+      body = ts.isBlock(node.body) ? Array.from(node.body.statements) :
+                                     [ts.factory.createReturnStatement(node.body)];
+    }
+
     return {
       node,
-      body: node.body !== undefined ? Array.from(node.body.statements) : null,
+      body,
+      typeParameters: node.typeParameters === undefined ? null : Array.from(node.typeParameters),
       parameters: node.parameters.map(param => {
         const name = parameterName(param.name);
         const initializer = param.initializer || null;
-        return {name, node: param, initializer};
+        return {name, node: param, initializer, type: param.type || null};
       }),
     };
   }