[sass-embedded] Error for simplifying custom function returned Calculation should not be treated as protocol error

[ntkme]

https://github.com/sass/sass/blob/524790175f9f236c9578217d2137b18e524e4e53/spec/embedded_sass.proto#L897-L900

  // The compiler must simplify any calculations it receives from the host
  // before returning them from a function. If this simplification produces an
  // error, it should be treated as though the function call threw that error.
  // It should *not* be treated as a protocol error.

Currently the embedded compiler throws a protocol error which causes compiler shutdown when user constructs an incorrect Calculation.

According to previous discussions (sass/embedded-protocol#98 & sass/dart-sass-embedded#118), for any host side input that the host relies on the compiler side logic for validation, the validation error should be result in CompileFailure instead of ProtocolError.

[ntkme]

Actually, what happens in the current implementation is that it sends a ProtocolError with id 4294967295 followed by a CompileFailure. For example:

<Sass::EmbeddedProtocol::OutboundMessage: error: <Sass::EmbeddedProtocol::ProtocolError: type: :PARAMS, id: 4294967295, message: "Value.Calculation.arguments must have exactly 3 arguments for clamp().">>

<Sass::EmbeddedProtocol::OutboundMessage: compile_response: <Sass::EmbeddedProtocol::OutboundMessage::CompileResponse: failure: <Sass::EmbeddedProtocol::OutboundMessage::CompileResponse::CompileFailure: message: "Value.Calculation.arguments must have exactly 3 arguments for clamp().", span: <Sass::EmbeddedProtocol::SourceSpan: text: "foo()", start: <Sass::EmbeddedProtocol::SourceSpan::SourceLocation: offset: 6, line: 0, column: 6>, end: <Sass::EmbeddedProtocol::SourceSpan::SourceLocation: offset: 11, line: 0, column: 11>, url: "", context: "a {b: foo()}">, stack_trace: "- 1:7  root stylesheet
", formatted: "Error: Value.Calculation.arguments must have exactly 3 arguments for clamp().
  ╷
1 │ a {b: foo()}
  │       ^^^^^
  ╵
  - 1:7  root stylesheet">, loaded_urls: []>>

[ntkme]

I think the actual problem is #2041. Closing this.