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Add a compile time error when passing arguments to regular HTML elements (e.g. <a @foo=) #1102

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fivetanley
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@fivetanley fivetanley commented May 18, 2020

Adds an error message in the compile phase to inform the developer that
@arguments are not allowed on HTML nodes. This can often come from
copy/pasting refactoring errors.

For example, given the following template:

<a href="https://emberjs.com" @onClick={{action "foo"}}>Ember.js</a>

Before, the developer would get a vague error at runtime (Example taken from
ember.js#18951
):

jquery.js:3827 Uncaught TypeError: func is not a function
    at StatementCompilers.compile (VM32 ember.debug.js:43121)
    at compileStatements (VM32 ember.debug.js:44323)
    at maybeCompile (VM32 ember.debug.js:44312)
    at CompilableTemplateImpl.compile (VM32 ember.debug.js:44292)
    at Object.evaluate (VM32 ember.debug.js:51011)
    at AppendOpcodes.evaluate (VM32 ember.debug.js:49382)
    at LowLevelVM.evaluateSyscall (VM32 ember.debug.js:52284)
    at LowLevelVM.evaluateInner (VM32 ember.debug.js:52240)
    at LowLevelVM.evaluateOuter (VM32 ember.debug.js:52232)
    at JitVM.next (VM32 ember.debug.js:53175)

Now, they get an error message that looks like:

SyntaxError: ${attribute.name} is not a valid attribute name. @arguments
are only allowed on components, but the tag for this element
(\`${elementNode.tag}\`) is a regular, non-component HTML element. (location
line and column)

Given that there's no special behavior glimmer adds for @arguments on regular
HTML nodes, and it seems invalid to put @ in attribute names in regular HTML
(validator.w3c.org gives Attribute @onclick is not serializable as XML 1.0
error message for the example template above), it seems helpful for the glimmer
compiler to fail at build time to prevent copy/paste errors and mistakes.

Fixes emberjs/ember.js#18951

@fivetanley fivetanley changed the title disallow @arguments on regular HTML nodes compile time error: disallow @arguments on regular HTML nodes May 18, 2020
@fivetanley fivetanley changed the title compile time error: disallow @arguments on regular HTML nodes [bugfix] compile time error: disallow @arguments on regular HTML nodes May 18, 2020
@fivetanley fivetanley force-pushed the disallow-at-arguments-on-regular-html-nodes branch from 3abccbf to f27f3f7 Compare May 18, 2020 16:19
Adds an error message in the compile phase to inform the developer that
`@arguments` are not allowed on HTML nodes. This can often come from
copy/pasting refactoring errors.

For example, given the following template:

```handlebars
<a href="https://emberjs.com" @OnClick={{action "foo"}}>Ember.js</a>
```

Before, the developer would get a vague error at runtime ([Example taken from
ember.js#18951](emberjs/ember.js#18951)):

```
jquery.js:3827 Uncaught TypeError: func is not a function
    at StatementCompilers.compile (VM32 ember.debug.js:43121)
    at compileStatements (VM32 ember.debug.js:44323)
    at maybeCompile (VM32 ember.debug.js:44312)
    at CompilableTemplateImpl.compile (VM32 ember.debug.js:44292)
    at Object.evaluate (VM32 ember.debug.js:51011)
    at AppendOpcodes.evaluate (VM32 ember.debug.js:49382)
    at LowLevelVM.evaluateSyscall (VM32 ember.debug.js:52284)
    at LowLevelVM.evaluateInner (VM32 ember.debug.js:52240)
    at LowLevelVM.evaluateOuter (VM32 ember.debug.js:52232)
    at JitVM.next (VM32 ember.debug.js:53175)
```

Now, they get an error message that looks like:

```
SyntaxError: ${attribute.name} is not a valid attribute name. @arguments
are only allowed on components, but the tag for this element
(\`${elementNode.tag}\`) is a regular, non-component HTML element. (location
line and column)
```

Given that there's no special behavior glimmer adds for `@arguments` on regular
HTML nodes, and it seems invalid to put `@` in attribute names in regular HTML
(validator.w3c.org gives ` Attribute @OnClick is not serializable as XML 1.0`
error message for the example template below), it seems helpful for the glimmer
compiler to fail at build time to prevent copy/paste errors and mistakes.

Fixes emberjs/ember.js#18951
@fivetanley fivetanley force-pushed the disallow-at-arguments-on-regular-html-nodes branch from f27f3f7 to f265f28 Compare May 18, 2020 16:21
@@ -55,6 +55,19 @@ function test(desc: string, template: string, ...expectedStatements: BuilderStat
const Append = Builder.Append;
const Concat = Builder.Concat;

QUnit.test(
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this doesn't match the test style in the rest of the file, which is a wrapper around QUnit.test and looks at wire format output. i thought it might be more clear to just use QUnit.test directly rather than extend the test function in this file to allow a callback/expect errors. Totally open to change this to whatever the maintainers prefer, let me know!

@rwjblue rwjblue requested a review from chancancode May 18, 2020 17:03
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This seems good to me, thanks for working on it @fivetanley!

Cross linking some of the other convo on this subject: ember-template-lint/ember-template-lint#927. Also somewhat related to ember-template-lint/ember-template-lint#1334 (though not 100%).

@rwjblue rwjblue added the bug label May 18, 2020
@rwjblue rwjblue changed the title [bugfix] compile time error: disallow @arguments on regular HTML nodes Add a compile time error when passing arguments to regular HTML elements (e.g. <a @foo=) May 18, 2020
@rwjblue rwjblue merged commit 4621c12 into glimmerjs:master May 18, 2020
@fivetanley fivetanley deleted the disallow-at-arguments-on-regular-html-nodes branch May 23, 2020 17:35
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passing @arguments to regular html elements doesn't give a great error message
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