Allow usage of this and arguments in nested function expression
#74179
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In #73059 we added build-time checks for the forbidden usage of `this` and `arguments` in server functions. A nested function expression is however allowed to use these expressions. x-ref: #74124 To add a bit more context: `this` is forbidden in server actions because the Next.js compiler hoists inline server actions out of their original location into the module scope, so that they can be imported and invoked by the action handler. Due to this hoisting, the `this` context gets lost and is not available to the server action. To prevent surprising runtime errors for such cases, we emit a build error to provide feedback to developers as early as possible. However, nested function declarations or function expressions create a new `this` context, and in those it's allowed to access `this` and `arguments`.
ijjk
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created-by: Next.js team
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maciej-ka
approved these changes
Dec 20, 2024
lubieowoce
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Dec 20, 2024
huozhi
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Dec 20, 2024
lubieowoce
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In #73059 we added build-time checks for the forbidden usage of
thisandargumentsin server functions. A nested function expression is however allowed to use these expressions.fixes #74181
To add a bit more context:
thisis forbidden in server actions because the Next.js compiler hoists inline server actions out of their original location into the module scope, so that they can be imported and invoked by the action handler. Due to this hoisting, thethiscontext gets lost and is not available to the server action.To prevent surprising runtime errors for such cases, we emit a build error to provide feedback to developers as early as possible.
However, nested function declarations or function expressions create a new
thiscontext, and in those it's allowed to accessthisandarguments.For consistency, and to prevent surprises when refactoring server actions, we apply the same rules for module-level server actions.