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feat(compiler): ability to mark an InvokeFunctionExpr as pure (#26860)

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Uglify and other tree-shakers attempt to determine if the invocation
of a function is side-effectful, and remove it if so (and the result
is unused). A /*@__PURE__*/ annotation on the call site can be used
to hint to the optimizer that the invocation has no side effects and
is safe to tree-shake away.

This commit adds a 'pure' flag to the output AST function call node,
which can be used to signal to downstream emitters that a pure
annotation should be added. It also modifies ngtsc's emitter to
emit an Uglify pure annotation when this flag is set.

Testing strategy: this will be tested via its consumers, by asserting
that pure functions are translated with the correct comment.

PR Close #26860
This commit is contained in:
Alex Rickabaugh
2018-10-30 10:05:12 -07:00
committed by Matias Niemelä
parent 4e9f2e5895
commit 4dfa71f018
2 changed files with 7 additions and 3 deletions
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6
packages/compiler-cli/src/ngtsc/translator/src/translator.ts
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@ -185,9 +185,13 @@ class ExpressionTranslatorVisitor implements ExpressionVisitor, StatementVisitor
}
visitInvokeFunctionExpr(ast: InvokeFunctionExpr, context: Context): ts.CallExpression {
return ts.createCall(
const expr = ts.createCall(
ast.fn.visitExpression(this, context), undefined,
ast.args.map(arg => arg.visitExpression(this, context)));
if (ast.pure) {
ts.addSyntheticLeadingComment(expr, ts.SyntaxKind.MultiLineCommentTrivia, '@__PURE__', false);
}
return expr;
}
visitInstantiateExpr(ast: InstantiateExpr, context: Context): ts.NewExpression {