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Special JSX children error message #7044

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Merged
merged 2 commits into from
Sep 24, 2024
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Special JSX children error message #7044

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special case error message when passing children to a JSX component t…
zth Sep 21, 2024
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zth Sep 21, 2024
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -22,6 +22,7 @@

#### :nail_care: Polish

- Improve error message when passing `children` prop to a component that doesn't accept it. https://github.com/rescript-lang/rescript-compiler/pull/7044
- Improve error messages for pattern matching on option vs non-option, and vice versa. https://github.com/rescript-lang/rescript-compiler/pull/7035
- Improve bigint literal comparison. https://github.com/rescript-lang/rescript-compiler/pull/7029
- Improve output of `@variadic` bindings. https://github.com/rescript-lang/rescript-compiler/pull/7030
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11 changes: 11 additions & 0 deletions jscomp/build_tests/super_errors/expected/component_missing_prop_children.res.expected
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@@ -0,0 +1,11 @@

We've found a bug for you!
/.../fixtures/component_missing_prop_children.res:6:35-42

4 │ type props<'name> = {name: 'name}
5 │
6 │ let make = (): props<'name> => {children: ""}
7 │ }
8 │

This JSX component does not accept child elements. It has no children prop
7 changes: 7 additions & 0 deletions jscomp/build_tests/super_errors/fixtures/component_missing_prop_children.res
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// Since the React transform isn't active in the tests, mimic what the transform outputs.
module Component = {
@res.jsxComponentProps
type props<'name> = {name: 'name}

let make = (): props<'name> => {children: ""}
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I don't get this. Is this really what the transform would output?

Why is the make function returning props? And not React.element?

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No it's not what the transform would output, but it doesn't matter, what matters is that a record of the given type is being created, which is what the transform would do. If we want to make this clearer we could set up a test suite with the transform enabled. But I don't know whether that's cumbersome to do. Do you know?

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@zth #7048

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@cknitt the problem now is that React itself isn't included. There's a react_ppx folder that does similar tests with the transform and React copied into the project itself. We could mimic that, but that's a larger change.

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@zth I don't think you need React, you can use the Jsx module that comes with the compiler.

E.g. something like

@jsx.component
let make = (~name) => Jsx.string(name)

should work fine.

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@cknitt cknitt Sep 23, 2024 •
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Ok, well, you don't need it in my example, but you are right, you need the externals for the JSX runtime if you want to use JSX.

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Yup.

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@cknitt let's just worry about the actual error message in this PR, and then we can figure out how to set up the React transform for this separately.

}
9 changes: 7 additions & 2 deletions jscomp/ml/error_message_utils.ml
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Expand Up @@ -278,8 +278,13 @@ let print_component_name ppf (p : Path.t) =
let print_component_wrong_prop_error ppf (p : Path.t)
(_fields : Types.label_declaration list) name =
fprintf ppf "@[<v>";
fprintf ppf
"@[<2>The prop @{<error>%s@} does not belong to the JSX component " name;
(match name with
| "children" ->
fprintf ppf
"@[<2>This JSX component does not accept child elements. It has no @{<error>children@} prop "
| _ ->
fprintf ppf
"@[<2>The prop @{<error>%s@} does not belong to the JSX component " name);
print_component_name ppf p;
fprintf ppf "@]@,@,"

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