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https://issues.apache.org/jira/browse/THRIFT-4060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15863020#comment-15863020
]
ASF GitHub Bot commented on THRIFT-4060:
----------------------------------------
Github user jeking3 commented on a diff in the pull request:
https://github.com/apache/thrift/pull/1172#discussion_r100707345
--- Diff: lib/cpp/test/AnnotationTest.cpp ---
@@ -0,0 +1,73 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+#define BOOST_TEST_MODULE AnnotationTest
+#include <boost/test/unit_test.hpp>
+#include "gen-cpp/AnnotationTest_types.h"
+#include <ostream>
+#include <sstream>
+
+// Normally thrift generates ostream operators, however
+// with the annotation "cpp.customostream" one can tell the
+// compiler they are going to provide their own, and not
+// emit operator << or printTo().
+
+std::ostream& operator<<(std::ostream& os, const ostr_custom& osc)
+{
+ os << "{ bar = " << osc.bar << "; }";
+ return os;
+}
+
+BOOST_AUTO_TEST_SUITE(BOOST_TEST_MODULE)
+
+BOOST_AUTO_TEST_CASE(test_cpp_customostream) {
+ //
+ // Show the compiler generated ostream operator does something..
+ //
+
+ ostr_default def;
+ def.__set_bar(10);
+
+ std::stringstream ssd;
+ ssd << def;
+ BOOST_CHECK_EQUAL(ssd.str(), "ostr_default(bar=10)");
+
+ //
+ // Now show that if cpp.customostream is added as an annotation,
+ // the behavior can be overridden in a safe and usable way (THRIFT-4060).
+ //
+
+ ostr_custom cus;
+ cus.__set_bar(10);
+
+ std::stringstream csd;
+ csd << cus;
+ BOOST_CHECK_EQUAL(csd.str(), "{ bar = 10; }");
--- End diff --
I split it out into two tests without comments.
> Thrift printTo ostream overload mechanism breaks down when types are nested
> ---------------------------------------------------------------------------
>
> Key: THRIFT-4060
> URL: https://issues.apache.org/jira/browse/THRIFT-4060
> Project: Thrift
> Issue Type: Bug
> Components: C++ - Compiler
> Affects Versions: 0.9.3, 0.10.0
> Environment: Ubuntu 14.04 LTS
> Reporter: James E. King, III
> Assignee: James E. King, III
>
> I'm in the middle of converting a project that provides some ostream
> operators (for logging purposes) for a number of thrift structures. The
> project was using 0.8.0 and in 0.9.3 some ostream operator overloads were
> added with THRIFT-3336. The solution that was provided here runs into
> complications if a thrift structure is contained within another one. Take
> this simple example:
> h4. Thrift
> {noformat}
> namespace cpp example.detail
> struct Lower {
> 1: binary lowerBinary
> }
> struct Higher {
> 1: set<Lower> lowers
> }
> {noformat}
> h4. C++
> {noformat}
> namespace example {
> class MyLower : public detail::Lower
> {
> virtual void printTo(std::ostream& os) const override;
> }
> class MyHigher : public detail::Higher
> {
> virtual void printTo(std::ostream& os) const override
> {
> os << lowers;
> // here's the problem, lowers is a set<detail::Lower> when it
> serializes in,
> // not a set<MyLower>, so I cannot override it...
> }
> }
> }
> {noformat}
> I'm considering adding an annotation to the thrift IDL that the compiler will
> recognize that allows someone to say, "I am going to provide my own
> operator<< for this structure, don't generate one". This would replace the
> printTo mechanism that was added in THRIFT-3336.
> Here is an example:
> {noformat}
> namespace cpp example.detail
> struct MyLower {
> 1: binary lowerBinary
> } (cpp.customostream)
> struct MyHigher {
> 1: set<Lower> lowers
> }
> {noformat}
> The annotation {{cpp.customostream}} (or the compiler option {{--gen
> cpp:no_ostream_operators}} for global effect) tells the compiler to emit only
> the declaration of the {{operator <<}} but does not emit a definition
> (implementation). It would be up to the implementation building against the
> generated code to provide an operator << if such an operator is needed for
> conversion to a stream (cout, lexical_cast to string, etc..).
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