89b8360218
CL 24800 changed the error representation from strings to objects.
However, since native errors types are not immediately compatible
across languages, wrapper types were introduced to bridge the gap.
This CL remove those wrappers and instead special case the error
proxy types to conform to their language error protocol.
Specifically:
- The ObjC proxy for Go errors now extends NSError and calls
initWithDomain to store the error message.
- The Go proxy for ObjC NSError return the localizedDescription
property for calls to Error.
- The Java proxy for Go errors ow extends Exception and
overrides getMessage() to return the error message.
- The Go proxy for Java Exceptions returns getMessage whenever
Error is called.
The end result is that error values behave more like normal objects
across the language boundary. In particular, instance identity is
now preserved: an error passed across the boundary and back will
result in the same instance.
There are two semantic changes that followed this change:
- The domain for wrapped Go errors is now always "go".
The domain wasn't useful before this CL: the domains were set to
the package name of function or method where the error happened
to cross the language boundary.
- If a Go method that returns an error is implemented in ObjC, the
implementation must now both return NO _and_ set the error result
for the calling Go code to receive a non-nil error.
Before this CL, because errors were always wrapped, a nil ObjC
could be represented with a non-nil wrapper.
Change-Id: Idb415b6b13ecf79ccceb60f675059942bfc48fec
Reviewed-on: https://go-review.googlesource.com/29298
Reviewed-by: David Crawshaw <crawshaw@golang.org>
53 lines
1.3 KiB
Plaintext
53 lines
1.3 KiB
Plaintext
// Java class go.issue12403.Parsable is a proxy for talking to a Go program.
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// gobind -lang=java issue12403
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//
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// File is generated by gobind. Do not edit.
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package go.issue12403;
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import go.Seq;
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public interface Parsable {
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public String fromJSON(String jstr);
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public String toJSON() throws Exception;
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}
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// Java class go.issue12403.Issue12403 is a proxy for talking to a Go program.
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// gobind -lang=java issue12403
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//
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// File is generated by gobind. Do not edit.
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package go.issue12403;
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import go.Seq;
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public abstract class Issue12403 {
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static {
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Seq.touch(); // for loading the native library
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_init();
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}
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private Issue12403() {} // uninstantiable
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// touch is called from other bound packages to initialize this package
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public static void touch() {}
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private static native void _init();
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private static final class proxyParsable implements Seq.Proxy, Parsable {
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private final Seq.Ref ref;
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@Override public final int incRefnum() {
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int refnum = ref.refnum;
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Seq.incGoRef(refnum);
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return refnum;
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}
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proxyParsable(Seq.Ref ref) { this.ref = ref; }
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public native String fromJSON(String jstr);
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public native String toJSON() throws Exception;
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}
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}
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