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Gabriel Schulhofmhdawson
Gabriel Schulhof
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mhdawson
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src: expose macros that throw errors
Macros `NAPI_THROW`, `NAPI_THROW_IF_FAILED`, and `NAPI_FATAL_IF_FAILED` have so far been used only in the implementation of node-addon-api. Nevertheless, they are useful in cases where direct N-API calls must be interspersed between normal node-addon-api usage. The greatest value they provide is that they convert non-`napi_ok` `napi_status` values into errors that can be thrown, and that they throw the errors respecting whether C++ exceptions are enabled or not. PR-URL: #448 Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com> Reviewed-By: Nicola Del Gobbo <nicoladelgobbo@NickNaso.local>
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‎doc/error_handling.md

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@@ -153,3 +153,34 @@ if (env.IsExceptionPending()) {
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Since the exception was cleared here, it will not be propagated as a JavaScript
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exception after the native callback returns.
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## Calling N-API directly from a **node-addon-api** addon
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**node-addon-api** provides macros for throwing errors in response to non-OK
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`napi_status` results when calling [N-API](https://nodejs.org/docs/latest/api/n-api.html)
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functions from within a native addon. These macros are defined differently
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depending on whether C++ exceptions are enabled or not, but are available for
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use in either case.
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### `NAPI_THROW(e, ...)`
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This macro accepts a `Napi::Error`, throws it, and returns the value given as
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the last parameter. If C++ exceptions are enabled (by defining
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`NAPI_CPP_EXCEPTIONS` during the build), the return value will be ignored.
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### `NAPI_THROW_IF_FAILED(env, status, ...)`
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This macro accepts a `Napi::Env` and a `napi_status`. It constructs an error
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from the `napi_status`, throws it, and returns the value given as the last
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parameter. If C++ exceptions are enabled (by defining `NAPI_CPP_EXCEPTIONS`
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during the build), the return value will be ignored.
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### `NAPI_THROW_IF_FAILED_VOID(env, status)`
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This macro accepts a `Napi::Env` and a `napi_status`. It constructs an error
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from the `napi_status`, throws it, and returns.
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### `NAPI_FATAL_IF_FAILED(status, location, message)`
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This macro accepts a `napi_status`, a C string indicating the location where the
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error occurred, and a second C string for the message to display.

‎napi-inl.h

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@@ -17,64 +17,6 @@ namespace Napi {
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// Helpers to handle functions exposed from C++.
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namespace details {
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#ifdef NAPI_CPP_EXCEPTIONS
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// When C++ exceptions are enabled, Errors are thrown directly. There is no need
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// to return anything after the throw statements. The variadic parameter is an
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// optional return value that is ignored.
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// We need _VOID versions of the macros to avoid warnings resulting from
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// leaving the NAPI_THROW_* `...` argument empty.
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#define NAPI_THROW(e, ...) throw e
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#define NAPI_THROW_VOID(e) throw e
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#define NAPI_THROW_IF_FAILED(env, status, ...) \
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if ((status) != napi_ok) throw Error::New(env);
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#define NAPI_THROW_IF_FAILED_VOID(env, status) \
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if ((status) != napi_ok) throw Error::New(env);
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#else // NAPI_CPP_EXCEPTIONS
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// When C++ exceptions are disabled, Errors are thrown as JavaScript exceptions,
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// which are pending until the callback returns to JS. The variadic parameter
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// is an optional return value; usually it is an empty result.
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// We need _VOID versions of the macros to avoid warnings resulting from
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// leaving the NAPI_THROW_* `...` argument empty.
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#define NAPI_THROW(e, ...) \
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do { \
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(e).ThrowAsJavaScriptException(); \
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return __VA_ARGS__; \
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} while (0)
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#define NAPI_THROW_VOID(e) \
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do { \
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(e).ThrowAsJavaScriptException(); \
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return; \
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} while (0)
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#define NAPI_THROW_IF_FAILED(env, status, ...) \
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if ((status) != napi_ok) { \
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Error::New(env).ThrowAsJavaScriptException(); \
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return __VA_ARGS__; \
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}
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#define NAPI_THROW_IF_FAILED_VOID(env, status) \
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if ((status) != napi_ok) { \
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Error::New(env).ThrowAsJavaScriptException(); \
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return; \
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}
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#endif // NAPI_CPP_EXCEPTIONS
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#define NAPI_FATAL_IF_FAILED(status, location, message) \
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do { \
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if ((status) != napi_ok) { \
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Error::Fatal((location), (message)); \
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} \
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} while (0)
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// Attach a data item to an object and delete it when the object gets
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// garbage-collected.
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// TODO: Replace this code with `napi_add_finalizer()` whenever it becomes
@@ -3705,10 +3647,6 @@ inline const napi_node_version* VersionManagement::GetNodeVersion(Env env) {
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return result;
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}
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// These macros shouldn't be useful in user code.
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#undef NAPI_THROW
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#undef NAPI_THROW_IF_FAILED
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} // namespace Napi
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#endif // SRC_NAPI_INL_H_

‎napi.h

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#define NAPI_NOEXCEPT noexcept
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#endif
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#ifdef NAPI_CPP_EXCEPTIONS
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// When C++ exceptions are enabled, Errors are thrown directly. There is no need
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// to return anything after the throw statements. The variadic parameter is an
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// optional return value that is ignored.
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// We need _VOID versions of the macros to avoid warnings resulting from
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// leaving the NAPI_THROW_* `...` argument empty.
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#define NAPI_THROW(e, ...) throw e
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#define NAPI_THROW_VOID(e) throw e
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#define NAPI_THROW_IF_FAILED(env, status, ...) \
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if ((status) != napi_ok) throw Error::New(env);
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#define NAPI_THROW_IF_FAILED_VOID(env, status) \
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if ((status) != napi_ok) throw Error::New(env);
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#else // NAPI_CPP_EXCEPTIONS
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// When C++ exceptions are disabled, Errors are thrown as JavaScript exceptions,
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// which are pending until the callback returns to JS. The variadic parameter
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// is an optional return value; usually it is an empty result.
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// We need _VOID versions of the macros to avoid warnings resulting from
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// leaving the NAPI_THROW_* `...` argument empty.
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#define NAPI_THROW(e, ...) \
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do { \
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(e).ThrowAsJavaScriptException(); \
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return __VA_ARGS__; \
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} while (0)
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#define NAPI_THROW_VOID(e) \
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do { \
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(e).ThrowAsJavaScriptException(); \
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return; \
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} while (0)
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#define NAPI_THROW_IF_FAILED(env, status, ...) \
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if ((status) != napi_ok) { \
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Error::New(env).ThrowAsJavaScriptException(); \
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return __VA_ARGS__; \
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}
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#define NAPI_THROW_IF_FAILED_VOID(env, status) \
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if ((status) != napi_ok) { \
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Error::New(env).ThrowAsJavaScriptException(); \
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return; \
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}
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#endif // NAPI_CPP_EXCEPTIONS
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#define NAPI_FATAL_IF_FAILED(status, location, message) \
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do { \
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if ((status) != napi_ok) { \
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Error::Fatal((location), (message)); \
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} \
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} while (0)
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////////////////////////////////////////////////////////////////////////////////
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/// N-API C++ Wrapper Classes
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///

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