refactor(@angular-devkit/build-optimizer): refactor assignment expression identification

Author: filipesilva

packages/angular_devkit/build_optimizer/src/transforms/scrub-file.ts

@@ -150,23 +150,10 @@ function isAngularCoreImport(node: ts.ImportDeclaration, isAngularCoreFile: bool
 
 // Check if assignment is `Clazz.decorators = [...];`.
 function isDecoratorAssignmentExpression(exprStmt: ts.ExpressionStatement): boolean {
-  if (exprStmt.expression.kind !== ts.SyntaxKind.BinaryExpression) {
+  if (!isAssignmentExpressionTo(exprStmt, 'decorators')) {
     return false;
   }
   const expr = exprStmt.expression as ts.BinaryExpression;
-  if (expr.left.kind !== ts.SyntaxKind.PropertyAccessExpression) {
-    return false;
-  }
-  const propAccess = expr.left as ts.PropertyAccessExpression;
-  if (propAccess.expression.kind !== ts.SyntaxKind.Identifier) {
-    return false;
-  }
-  if (propAccess.name.text !== 'decorators') {
-    return false;
-  }
-  if (expr.operatorToken.kind !== ts.SyntaxKind.FirstAssignment) {
-    return false;
-  }
   if (expr.right.kind !== ts.SyntaxKind.ArrayLiteralExpression) {
     return false;
   }
@@ -275,32 +262,33 @@ function isAngularDecoratorMetadataExpression(
 
 // Check if assignment is `Clazz.propDecorators = [...];`.
 function isPropDecoratorAssignmentExpression(exprStmt: ts.ExpressionStatement): boolean {
-  if (exprStmt.expression.kind !== ts.SyntaxKind.BinaryExpression) {
+  if (!isAssignmentExpressionTo(exprStmt, 'propDecorators')) {
     return false;
   }
   const expr = exprStmt.expression as ts.BinaryExpression;
-  if (expr.left.kind !== ts.SyntaxKind.PropertyAccessExpression) {
-    return false;
-  }
-  const propAccess = expr.left as ts.PropertyAccessExpression;
-  if (propAccess.expression.kind !== ts.SyntaxKind.Identifier) {
-    return false;
-  }
-  if (propAccess.name.text !== 'propDecorators') {
+  if (expr.right.kind !== ts.SyntaxKind.ObjectLiteralExpression) {
     return false;
   }
-  if (expr.operatorToken.kind !== ts.SyntaxKind.FirstAssignment) {
+
+  return true;
+}
+
+// Check if assignment is `Clazz.ctorParameters = [...];`.
+function isCtorParamsAssignmentExpression(exprStmt: ts.ExpressionStatement): boolean {
+  if (!isAssignmentExpressionTo(exprStmt, 'ctorParameters')) {
     return false;
   }
-  if (expr.right.kind !== ts.SyntaxKind.ObjectLiteralExpression) {
+  const expr = exprStmt.expression as ts.BinaryExpression;
+  if (expr.right.kind !== ts.SyntaxKind.FunctionExpression
+    && expr.right.kind !== ts.SyntaxKind.ArrowFunction
+  ) {
     return false;
   }
 
   return true;
 }
 
-// Check if assignment is `Clazz.ctorParameters = [...];`.
-function isCtorParamsAssignmentExpression(exprStmt: ts.ExpressionStatement): boolean {
+function isAssignmentExpressionTo(exprStmt: ts.ExpressionStatement, name: string) {
   if (exprStmt.expression.kind !== ts.SyntaxKind.BinaryExpression) {
     return false;
   }
@@ -309,7 +297,7 @@ function isCtorParamsAssignmentExpression(exprStmt: ts.ExpressionStatement): boo
     return false;
   }
   const propAccess = expr.left as ts.PropertyAccessExpression;
-  if (propAccess.name.text !== 'ctorParameters') {
+  if (propAccess.name.text !== name) {
     return false;
   }
   if (propAccess.expression.kind !== ts.SyntaxKind.Identifier) {
@@ -318,11 +306,6 @@ function isCtorParamsAssignmentExpression(exprStmt: ts.ExpressionStatement): boo
   if (expr.operatorToken.kind !== ts.SyntaxKind.FirstAssignment) {
     return false;
   }
-  if (expr.right.kind !== ts.SyntaxKind.FunctionExpression
-    && expr.right.kind !== ts.SyntaxKind.ArrowFunction
-  ) {
-    return false;
-  }
 
   return true;
 }