ml_parser - leading '&#' leads to a cryptic error

I’m submitting a…

[ ] Regression (a behavior that used to work and stopped working in a new release)
[X] Bug report  
[ ] Performance issue
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question
[ ] Other... Please describe:

Current behavior

Any attribute value with an leading &# will throw:

Template parse errors:
Unexpected character "'" ("<hello name="{{ name }}" [icon]="'&#[ERROR ->]'"></hello>
<p>
Start editing to see some magic happen :)
"): ng:///AppModule/AppComponent.html@0:36
Unexpected closing tag "hello". It may happen when the tag has already been closed by another tag. For more info see https://www.w3.org/TR/html5/syntax.html#closing-elements-that-have-implied-end-tags ("<hello name="{{ name }}" [icon]="'&#'">[ERROR ->]</hello>
<p>
Start editing to see some magic happen :)
"): ng:///AppModule/AppComponent.html@0:39
Evaluating src/main.ts
Booting application

Expected behavior

1. The parser should point to the exact issue that an entity was expected. The error message here should be more meaningful. or
2. The parser should proceed and handle it as text because parser can’t know if it’s an entity. or
3. or Handle e.g &#333 as ō that’s the behaviour of parse5

But we can definitly improve the error message.

Minimal reproduction of the problem with instructions

https://stackblitz.com/edit/angular-fjgsqz?file=src/app/app.component.html

What is the motivation / use case for changing the behavior?

User should get the correct error message

Environment

Angular version: 6.0.0

[manklu]

@StarpTech

The second point is that this error is very cryptic

I have never said the error message is good 😏

[manklu]

The parser should proceed and handle it as text because parser can’t know if it’s an entity.

Per html definition, anything that starts with an ampersand is an entity. If you want to output one you should use &.

Handle e.g &#333 as ō that’s the behaviour of parse5

If you use the correct syntax it works: ō