fix: Change format when elements are truncated and add additional tests

Author: david1437

cpp/src/arrow/pretty_print.cc

@@ -59,7 +59,9 @@ class PrettyPrinter {
       : options_(options), indent_(options.indent), sink_(sink) {}
 
   inline void Write(std::string_view data);
+  inline void Write(std::string_view data, const int max_chars);
   inline void WriteIndented(std::string_view data);
+  inline void WriteIndented(std::string_view data, const int max_chars);
   inline void Newline();
   inline void Indent();
   inline void IndentAfterNewline();
@@ -105,20 +107,29 @@ void PrettyPrinter::CloseArray(const Array& array) {
 }
 
 void PrettyPrinter::Write(std::string_view data) {
-  int available_chars = options_.element_size_limit;
-  for (size_t i = 0; i < data.size(); ++i) {
-    if (available_chars-- > 0) {
-      sink_->put(data[i]);
+  Write(data, options_.element_size_limit);
+}
+
+void PrettyPrinter::Write(std::string_view data, const int max_chars) {
+  int curr_max = max_chars;
+  for (auto c : data) {
+    if (curr_max-- > 0) {
+      sink_->put(c);
     } else {
-      (*sink_) << "+" << data.size() - options_.element_size_limit;
+      (*sink_) << " (... " << data.size() - max_chars << " chars omitted)";
       return;
     }
   }
 }
 
 void PrettyPrinter::WriteIndented(std::string_view data) {
   Indent();
-  Write(data);
+  Write(data, options_.element_size_limit);
+}
+
+void PrettyPrinter::WriteIndented(std::string_view data, const int max_chars) {
+  Indent();
+  Write(data, max_chars);
 }
 
 void PrettyPrinter::Newline() {
@@ -242,7 +253,9 @@ class ArrayPrinter : public PrettyPrinter {
   enable_if_has_string_view<T, Status> WriteDataValues(const ArrayType& array) {
     return WriteValues(array, [&](int64_t i) {
       if constexpr (T::is_utf8) {
-        this->Write("\"" + std::string{array.GetView(i)} + "\"");
+        (*sink_) << "\"";
+        this->Write(array.GetView(i), options_.element_size_limit - 2);
+        (*sink_) << "\"";
       } else {
         this->Write(HexEncode(array.GetView(i)));
       }

cpp/src/arrow/pretty_print_test.cc

@@ -177,6 +177,18 @@ TEST_F(TestPrettyPrint, PrimitiveType) {
   ])expected";
   CheckPrimitive<StringType, std::string>({2, 10}, is_valid, values3, ex3_in2);
   CheckPrimitive<LargeStringType, std::string>({2, 10}, is_valid, values3, ex3_in2);
+
+  PrettyPrintOptions options{2, 10};
+  options.element_size_limit = 2;
+  static const char* ex3_in3 = R"expected(  [
+    " (... 3 chars omitted)",
+    " (... 3 chars omitted)",
+    null,
+    " (... 3 chars omitted)",
+    null
+  ])expected";
+  CheckPrimitive<StringType, std::string>(options, is_valid, values3, ex3_in3);
+  CheckPrimitive<LargeStringType, std::string>(options, is_valid, values3, ex3_in3);
 }
 
 TEST_F(TestPrettyPrint, PrimitiveTypeNoNewlines) {
@@ -775,7 +787,8 @@ TEST_F(TestPrettyPrint, BinaryNoNewlines) {
 
   // With truncated element size
   options.element_size_limit = 1;
-  expected = "[6+5,6+5,...,,F+1]";
+  expected =
+      "[6 (... 5 chars omitted),6 (... 5 chars omitted),...,,F (... 1 chars omitted)]";
   CheckPrimitive<BinaryType, std::string>(options, is_valid, values, expected, false);
 }
 
@@ -1108,6 +1121,12 @@ TEST_F(TestPrettyPrint, FixedSizeBinaryType) {
   CheckArray(*array, {0, 10}, ex);
   static const char* ex_2 = "  [\n    666F6F,\n    ...\n    62617A\n  ]";
   CheckArray(*array, {2, 1}, ex_2);
+
+  auto options = PrettyPrintOptions{2, 1};
+  options.element_size_limit = 3;
+  static const char* ex_3 =
+      "  [\n    666 (... 3 chars omitted),\n    ...\n    626 (... 3 chars omitted)\n  ]";
+  CheckArray(*array, options, ex_3);
 }
 
 TEST_F(TestPrettyPrint, DecimalTypes) {