unittests/ADT/FallibleIteratorTest.cpp

   1 //===- unittests/ADT/FallibleIteratorTest.cpp - fallible_iterator.h tests -===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/ADT/fallible_iterator.h"
  10 #include "llvm/Testing/Support/Error.h"
  11
  12 #include "gtest/gtest-spi.h"
  13 #include "gtest/gtest.h"
  14
  15 #include <utility>
  16 #include <vector>
  17
  18 using namespace llvm;
  19
  20 namespace {
  21
  22 using ItemValid = enum { ValidItem, InvalidItem };
  23 using LinkValid = enum { ValidLink, InvalidLink };
  24
  25 class Item {
  26 public:
  27   Item(ItemValid V) : V(V) {}
  28   bool isValid() const { return V == ValidItem; }
  29
  30 private:
  31   ItemValid V;
  32 };
  33
  34 // A utility to mock "bad collections". It supports both invalid items,
  35 // where the dereference operator may return an Error, and bad links
  36 // where the inc/dec operations may return an Error.
  37 // Each element of the mock collection contains a pair of a (possibly broken)
  38 // item and link.
  39 using FallibleCollection = std::vector<std::pair<Item, LinkValid>>;
  40
  41 class FallibleCollectionWalker {
  42 public:
  43   FallibleCollectionWalker(FallibleCollection &C, unsigned Idx)
  44       : C(C), Idx(Idx) {}
  45
  46   Item &operator*() { return C[Idx].first; }
  47
  48   const Item &operator*() const { return C[Idx].first; }
  49
  50   Error inc() {
  51     assert(Idx != C.size() && "Walking off end of (mock) collection");
  52     if (C[Idx].second == ValidLink) {
  53       ++Idx;
  54       return Error::success();
  55     }
  56     return make_error<StringError>("cant get next object in (mock) collection",
  57                                    inconvertibleErrorCode());
  58   }
  59
  60   Error dec() {
  61     assert(Idx != 0 && "Walking off start of (mock) collection");
  62     --Idx;
  63     if (C[Idx].second == ValidLink)
  64       return Error::success();
  65     return make_error<StringError>("cant get prev object in (mock) collection",
  66                                    inconvertibleErrorCode());
  67   }
  68
  69   friend bool operator==(const FallibleCollectionWalker &LHS,
  70                          const FallibleCollectionWalker &RHS) {
  71     assert(&LHS.C == &RHS.C && "Comparing iterators across collectionss.");
  72     return LHS.Idx == RHS.Idx;
  73   }
  74
  75 private:
  76   FallibleCollection &C;
  77   unsigned Idx;
  78 };
  79
  80 class FallibleCollectionWalkerWithStructDeref
  81     : public FallibleCollectionWalker {
  82 public:
  83   using FallibleCollectionWalker::FallibleCollectionWalker;
  84
  85   Item *operator->() { return &this->operator*(); }
  86
  87   const Item *operator->() const { return &this->operator*(); }
  88 };
  89
  90 class FallibleCollectionWalkerWithFallibleDeref
  91     : public FallibleCollectionWalker {
  92 public:
  93   using FallibleCollectionWalker::FallibleCollectionWalker;
  94
  95   Expected<Item &> operator*() {
  96     auto &I = FallibleCollectionWalker::operator*();
  97     if (!I.isValid())
  98       return make_error<StringError>("bad item", inconvertibleErrorCode());
  99     return I;
 100   }
 101
 102   Expected<const Item &> operator*() const {
 103     const auto &I = FallibleCollectionWalker::operator*();
 104     if (!I.isValid())
 105       return make_error<StringError>("bad item", inconvertibleErrorCode());
 106     return I;
 107   }
 108 };
 109
 110 TEST(FallibleIteratorTest, BasicSuccess) {
 111
 112   // Check that a basic use-case involing successful iteration over a
 113   // "FallibleCollection" works.
 114
 115   FallibleCollection C({{ValidItem, ValidLink}, {ValidItem, ValidLink}});
 116
 117   FallibleCollectionWalker begin(C, 0);
 118   FallibleCollectionWalker end(C, 2);
 119
 120   Error Err = Error::success();
 121   for (auto &Elem :
 122        make_fallible_range<FallibleCollectionWalker>(begin, end, Err))
 123     EXPECT_TRUE(Elem.isValid());
 124   cantFail(std::move(Err));
 125 }
 126
 127 TEST(FallibleIteratorTest, BasicFailure) {
 128
 129   // Check that a iteration failure (due to the InvalidLink state on element one
 130   // of the fallible collection) breaks out of the loop and raises an Error.
 131
 132   FallibleCollection C({{ValidItem, ValidLink}, {ValidItem, InvalidLink}});
 133
 134   FallibleCollectionWalker begin(C, 0);
 135   FallibleCollectionWalker end(C, 2);
 136
 137   Error Err = Error::success();
 138   for (auto &Elem :
 139        make_fallible_range<FallibleCollectionWalker>(begin, end, Err))
 140     EXPECT_TRUE(Elem.isValid());
 141
 142   EXPECT_THAT_ERROR(std::move(Err), Failed()) << "Expected failure value";
 143 }
 144
 145 TEST(FallibleIteratorTest, NoRedundantErrorCheckOnEarlyExit) {
 146
 147   // Check that an early return from the loop body does not require a redundant
 148   // check of Err.
 149
 150   FallibleCollection C({{ValidItem, ValidLink}, {ValidItem, ValidLink}});
 151
 152   FallibleCollectionWalker begin(C, 0);
 153   FallibleCollectionWalker end(C, 2);
 154
 155   Error Err = Error::success();
 156   for (auto &Elem :
 157        make_fallible_range<FallibleCollectionWalker>(begin, end, Err)) {
 158     (void)Elem;
 159     return;
 160   }
 161   // Err not checked, but should be ok because we exit from the loop
 162   // body.
 163 }
 164
 165 #if LLVM_ENABLE_ABI_BREAKING_CHECKS
 166 TEST(FallibleIteratorTest, RegularLoopExitRequiresErrorCheck) {
 167
 168   // Check that Err must be checked after a normal (i.e. not early) loop exit
 169   // by failing to check and expecting program death (due to the unchecked
 170   // error).
 171
 172   EXPECT_DEATH(
 173       {
 174         FallibleCollection C({{ValidItem, ValidLink}, {ValidItem, ValidLink}});
 175
 176         FallibleCollectionWalker begin(C, 0);
 177         FallibleCollectionWalker end(C, 2);
 178
 179         Error Err = Error::success();
 180         for (auto &Elem :
 181              make_fallible_range<FallibleCollectionWalker>(begin, end, Err))
 182           (void)Elem;
 183       },
 184       "Program aborted due to an unhandled Error:")
 185       << "Normal (i.e. not early) loop exit should require an error check";
 186 }
 187 #endif
 188
 189 TEST(FallibleIteratorTest, RawIncrementAndDecrementBehavior) {
 190
 191   // Check the exact behavior of increment / decrement.
 192
 193   FallibleCollection C({{ValidItem, ValidLink},
 194                         {ValidItem, InvalidLink},
 195                         {ValidItem, ValidLink},
 196                         {ValidItem, InvalidLink}});
 197
 198   {
 199     // One increment from begin succeeds.
 200     Error Err = Error::success();
 201     auto I = make_fallible_itr(FallibleCollectionWalker(C, 0), Err);
 202     ++I;
 203     EXPECT_THAT_ERROR(std::move(Err), Succeeded());
 204   }
 205
 206   {
 207     // Two increments from begin fail.
 208     Error Err = Error::success();
 209     auto I = make_fallible_itr(FallibleCollectionWalker(C, 0), Err);
 210     ++I;
 211     EXPECT_THAT_ERROR(std::move(Err), Succeeded());
 212     ++I;
 213     EXPECT_THAT_ERROR(std::move(Err), Failed()) << "Expected failure value";
 214   }
 215
 216   {
 217     // One decement from element three succeeds.
 218     Error Err = Error::success();
 219     auto I = make_fallible_itr(FallibleCollectionWalker(C, 3), Err);
 220     --I;
 221     EXPECT_THAT_ERROR(std::move(Err), Succeeded());
 222   }
 223
 224   {
 225     // One decement from element three succeeds.
 226     Error Err = Error::success();
 227     auto I = make_fallible_itr(FallibleCollectionWalker(C, 3), Err);
 228     --I;
 229     EXPECT_THAT_ERROR(std::move(Err), Succeeded());
 230     --I;
 231     EXPECT_THAT_ERROR(std::move(Err), Failed());
 232   }
 233 }
 234
 235 TEST(FallibleIteratorTest, CheckStructDerefOperatorSupport) {
 236   // Check that the fallible_iterator wrapper forwards through to the
 237   // underlying iterator's structure dereference operator if present.
 238
 239   FallibleCollection C({{ValidItem, ValidLink},
 240                         {ValidItem, ValidLink},
 241                         {InvalidItem, InvalidLink}});
 242
 243   FallibleCollectionWalkerWithStructDeref begin(C, 0);
 244
 245   {
 246     Error Err = Error::success();
 247     auto I = make_fallible_itr(begin, Err);
 248     EXPECT_TRUE(I->isValid());
 249     cantFail(std::move(Err));
 250   }
 251
 252   {
 253     Error Err = Error::success();
 254     const auto I = make_fallible_itr(begin, Err);
 255     EXPECT_TRUE(I->isValid());
 256     cantFail(std::move(Err));
 257   }
 258 }
 259
 260 TEST(FallibleIteratorTest, CheckDerefToExpectedSupport) {
 261
 262   // Check that the fallible_iterator wrapper forwards value types, in
 263   // particular llvm::Expected, correctly.
 264
 265   FallibleCollection C({{ValidItem, ValidLink},
 266                         {InvalidItem, ValidLink},
 267                         {ValidItem, ValidLink}});
 268
 269   FallibleCollectionWalkerWithFallibleDeref begin(C, 0);
 270   FallibleCollectionWalkerWithFallibleDeref end(C, 3);
 271
 272   Error Err = Error::success();
 273   auto I = make_fallible_itr(begin, Err);
 274   auto E = make_fallible_end(end);
 275
 276   Expected<Item> V1 = *I;
 277   EXPECT_THAT_ERROR(V1.takeError(), Succeeded());
 278   ++I;
 279   EXPECT_NE(I, E); // Implicitly check error.
 280   Expected<Item> V2 = *I;
 281   EXPECT_THAT_ERROR(V2.takeError(), Failed());
 282   ++I;
 283   EXPECT_NE(I, E); // Implicitly check error.
 284   Expected<Item> V3 = *I;
 285   EXPECT_THAT_ERROR(V3.takeError(), Succeeded());
 286   ++I;
 287   EXPECT_EQ(I, E);
 288   cantFail(std::move(Err));
 289 }
 290
 291 } // namespace