Lift JSON library from clang-tools-extra/clangd to llvm/Support.

Summary:
This consists of four main parts:
 - an type json::Expr representing JSON values of dynamic kind, which can be
   composed, inspected, and modified
 - a JSON parser from string -> json::Expr
 - a JSON printer from json::Expr -> string, with optional pretty-printing
 - a convention for mapping json::Expr <=> native types (fromJSON/toJSON)
   Mapping functions are provided for primitives (e.g. int, vector) and the
   ObjectMapper helper helps implement fromJSON for struct/object types.

Based on clangd's usage, a couple of places I'd appreciate review attention:
 - fromJSON returns only bool. A richer error-signaling mechanism may be useful
   to provide useful messages, or let recursive fromJSONs (containers/structs)
   do careful error recovery.
 - should json::obj be always explicitly written (like json::ary)
 - there's no streaming parse API. I suspect there are some simple wins like
   a callback API where the document is a long array, and each element is small.
   But this can probably be bolted on easily when we see the need.

Reviewers: bkramer, labath

Subscribers: mgorny, ilya-biryukov, ioeric, MaskRay, llvm-commits

Differential Revision: https://reviews.llvm.org/D45753

llvm-svn: 336534

2 files changed, 293 insertions, 0 deletions

diff --git a/llvm/unittests/Support/CMakeLists.txt b/llvm/unittests/Support/CMakeLists.txt
index 852180c5cf9..266a389b8b7 100644
--- a/llvm/unittests/Support/CMakeLists.txt
+++ b/llvm/unittests/Support/CMakeLists.txt
@@ -30,6 +30,7 @@ add_llvm_unittest(SupportTests
   FormatVariadicTest.cpp
   GlobPatternTest.cpp
   Host.cpp
+  JSONTest.cpp
   LEB128Test.cpp
   LineIteratorTest.cpp
   LockFileManagerTest.cpp
diff --git a/llvm/unittests/Support/JSONTest.cpp b/llvm/unittests/Support/JSONTest.cpp
new file mode 100644
index 00000000000..bf7f4ae96d0
--- /dev/null
+++ b/llvm/unittests/Support/JSONTest.cpp
@@ -0,0 +1,292 @@
+//===-- JSONTest.cpp - JSON unit tests --------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/JSON.h"
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace llvm {
+namespace json {
+
+namespace {
+
+std::string s(const Value &E) { return llvm::formatv("{0}", E).str(); }
+std::string sp(const Value &E) { return llvm::formatv("{0:2}", E).str(); }
+
+TEST(JSONTest, Types) {
+  EXPECT_EQ("true", s(true));
+  EXPECT_EQ("null", s(nullptr));
+  EXPECT_EQ("2.5", s(2.5));
+  EXPECT_EQ(R"("foo")", s("foo"));
+  EXPECT_EQ("[1,2,3]", s({1, 2, 3}));
+  EXPECT_EQ(R"({"x":10,"y":20})", s(Object{{"x", 10}, {"y", 20}}));
+}
+
+TEST(JSONTest, Constructors) {
+  // Lots of edge cases around empty and singleton init lists.
+  EXPECT_EQ("[[[3]]]", s({{{3}}}));
+  EXPECT_EQ("[[[]]]", s({{{}}}));
+  EXPECT_EQ("[[{}]]", s({{Object{}}}));
+  EXPECT_EQ(R"({"A":{"B":{}}})", s(Object{{"A", Object{{"B", Object{}}}}}));
+  EXPECT_EQ(R"({"A":{"B":{"X":"Y"}}})",
+            s(Object{{"A", Object{{"B", Object{{"X", "Y"}}}}}}));
+}
+
+TEST(JSONTest, StringOwnership) {
+  char X[] = "Hello";
+  Value Alias = static_cast<const char *>(X);
+  X[1] = 'a';
+  EXPECT_EQ(R"("Hallo")", s(Alias));
+
+  std::string Y = "Hello";
+  Value Copy = Y;
+  Y[1] = 'a';
+  EXPECT_EQ(R"("Hello")", s(Copy));
+}
+
+TEST(JSONTest, CanonicalOutput) {
+  // Objects are sorted (but arrays aren't)!
+  EXPECT_EQ(R"({"a":1,"b":2,"c":3})", s(Object{{"a", 1}, {"c", 3}, {"b", 2}}));
+  EXPECT_EQ(R"(["a","c","b"])", s({"a", "c", "b"}));
+  EXPECT_EQ("3", s(3.0));
+}
+
+TEST(JSONTest, Escaping) {
+  std::string test = {
+      0,                    // Strings may contain nulls.
+      '\b',   '\f',         // Have mnemonics, but we escape numerically.
+      '\r',   '\n',   '\t', // Escaped with mnemonics.
+      'S',    '\"',   '\\', // Printable ASCII characters.
+      '\x7f',               // Delete is not escaped.
+      '\xce', '\x94',       // Non-ASCII UTF-8 is not escaped.
+  };
+
+  std::string teststring = R"("\u0000\u0008\u000c\r\n\tS\"\\)"
+                           "\x7f\xCE\x94\"";
+
+  EXPECT_EQ(teststring, s(test));
+
+  EXPECT_EQ(R"({"object keys are\nescaped":true})",
+            s(Object{{"object keys are\nescaped", true}}));
+}
+
+TEST(JSONTest, PrettyPrinting) {
+  const char str[] = R"({
+  "empty_array": [],
+  "empty_object": {},
+  "full_array": [
+    1,
+    null
+  ],
+  "full_object": {
+    "nested_array": [
+      {
+        "property": "value"
+      }
+    ]
+  }
+})";
+
+  EXPECT_EQ(str, sp(Object{
+                     {"empty_object", Object{}},
+                     {"empty_array", {}},
+                     {"full_array", {1, nullptr}},
+                     {"full_object",
+                      Object{
+                          {"nested_array",
+                           {Object{
+                               {"property", "value"},
+                           }}},
+                      }},
+                 }));
+}
+
+TEST(JSONTest, Parse) {
+  auto Compare = [](llvm::StringRef S, Value Expected) {
+    if (auto E = parse(S)) {
+      // Compare both string forms and with operator==, in case we have bugs.
+      EXPECT_EQ(*E, Expected);
+      EXPECT_EQ(sp(*E), sp(Expected));
+    } else {
+      handleAllErrors(E.takeError(), [S](const llvm::ErrorInfoBase &E) {
+        FAIL() << "Failed to parse JSON >>> " << S << " <<<: " << E.message();
+      });
+    }
+  };
+
+  Compare(R"(true)", true);
+  Compare(R"(false)", false);
+  Compare(R"(null)", nullptr);
+
+  Compare(R"(42)", 42);
+  Compare(R"(2.5)", 2.5);
+  Compare(R"(2e50)", 2e50);
+  Compare(R"(1.2e3456789)", std::numeric_limits<double>::infinity());
+
+  Compare(R"("foo")", "foo");
+  Compare(R"("\"\\\b\f\n\r\t")", "\"\\\b\f\n\r\t");
+  Compare(R"("\u0000")", llvm::StringRef("\0", 1));
+  Compare("\"\x7f\"", "\x7f");
+  Compare(R"("\ud801\udc37")", u8"\U00010437"); // UTF16 surrogate pair escape.
+  Compare("\"\xE2\x82\xAC\xF0\x9D\x84\x9E\"", u8"\u20ac\U0001d11e"); // UTF8
+  Compare(
+      R"("LoneLeading=\ud801, LoneTrailing=\udc01, LeadingLeadingTrailing=\ud801\ud801\udc37")",
+      u8"LoneLeading=\ufffd, LoneTrailing=\ufffd, "
+      u8"LeadingLeadingTrailing=\ufffd\U00010437"); // Invalid unicode.
+
+  Compare(R"({"":0,"":0})", Object{{"", 0}});
+  Compare(R"({"obj":{},"arr":[]})", Object{{"obj", Object{}}, {"arr", {}}});
+  Compare(R"({"\n":{"\u0000":[[[[]]]]}})",
+          Object{{"\n", Object{
+                            {llvm::StringRef("\0", 1), {{{{}}}}},
+                        }}});
+  Compare("\r[\n\t] ", {});
+}
+
+TEST(JSONTest, ParseErrors) {
+  auto ExpectErr = [](llvm::StringRef Msg, llvm::StringRef S) {
+    if (auto E = parse(S)) {
+      // Compare both string forms and with operator==, in case we have bugs.
+      FAIL() << "Parsed JSON >>> " << S << " <<< but wanted error: " << Msg;
+    } else {
+      handleAllErrors(E.takeError(), [S, Msg](const llvm::ErrorInfoBase &E) {
+        EXPECT_THAT(E.message(), testing::HasSubstr(Msg)) << S;
+      });
+    }
+  };
+  ExpectErr("Unexpected EOF", "");
+  ExpectErr("Unexpected EOF", "[");
+  ExpectErr("Text after end of document", "[][]");
+  ExpectErr("Invalid JSON value (false?)", "fuzzy");
+  ExpectErr("Expected , or ]", "[2?]");
+  ExpectErr("Expected object key", "{a:2}");
+  ExpectErr("Expected : after object key", R"({"a",2})");
+  ExpectErr("Expected , or } after object property", R"({"a":2 "b":3})");
+  ExpectErr("Invalid JSON value", R"([&%!])");
+  ExpectErr("Invalid JSON value (number?)", "1e1.0");
+  ExpectErr("Unterminated string", R"("abc\"def)");
+  ExpectErr("Control character in string", "\"abc\ndef\"");
+  ExpectErr("Invalid escape sequence", R"("\030")");
+  ExpectErr("Invalid \\u escape sequence", R"("\usuck")");
+  ExpectErr("[3:3, byte=19]", R"({
+  "valid": 1,
+  invalid: 2
+})");
+}
+
+TEST(JSONTest, Inspection) {
+  llvm::Expected<Value> Doc = parse(R"(
+    {
+      "null": null,
+      "boolean": false,
+      "number": 2.78,
+      "string": "json",
+      "array": [null, true, 3.14, "hello", [1,2,3], {"time": "arrow"}],
+      "object": {"fruit": "banana"}
+    }
+  )");
+  EXPECT_TRUE(!!Doc);
+
+  Object *O = Doc->getAsObject();
+  ASSERT_TRUE(O);
+
+  EXPECT_FALSE(O->getNull("missing"));
+  EXPECT_FALSE(O->getNull("boolean"));
+  EXPECT_TRUE(O->getNull("null"));
+
+  EXPECT_EQ(O->getNumber("number"), llvm::Optional<double>(2.78));
+  EXPECT_FALSE(O->getInteger("number"));
+  EXPECT_EQ(O->getString("string"), llvm::Optional<llvm::StringRef>("json"));
+  ASSERT_FALSE(O->getObject("missing"));
+  ASSERT_FALSE(O->getObject("array"));
+  ASSERT_TRUE(O->getObject("object"));
+  EXPECT_EQ(*O->getObject("object"), (Object{{"fruit", "banana"}}));
+
+  Array *A = O->getArray("array");
+  ASSERT_TRUE(A);
+  EXPECT_EQ((*A)[1].getAsBoolean(), llvm::Optional<bool>(true));
+  ASSERT_TRUE((*A)[4].getAsArray());
+  EXPECT_EQ(*(*A)[4].getAsArray(), (Array{1, 2, 3}));
+  EXPECT_EQ((*(*A)[4].getAsArray())[1].getAsInteger(),
+            llvm::Optional<int64_t>(2));
+  int I = 0;
+  for (Value &E : *A) {
+    if (I++ == 5) {
+      ASSERT_TRUE(E.getAsObject());
+      EXPECT_EQ(E.getAsObject()->getString("time"),
+                llvm::Optional<llvm::StringRef>("arrow"));
+    } else
+      EXPECT_FALSE(E.getAsObject());
+  }
+}
+
+// Sample struct with typical JSON-mapping rules.
+struct CustomStruct {
+  CustomStruct() : B(false) {}
+  CustomStruct(std::string S, llvm::Optional<int> I, bool B)
+      : S(S), I(I), B(B) {}
+  std::string S;
+  llvm::Optional<int> I;
+  bool B;
+};
+inline bool operator==(const CustomStruct &L, const CustomStruct &R) {
+  return L.S == R.S && L.I == R.I && L.B == R.B;
+}
+inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
+                                     const CustomStruct &S) {
+  return OS << "(" << S.S << ", " << (S.I ? std::to_string(*S.I) : "None")
+            << ", " << S.B << ")";
+}
+bool fromJSON(const Value &E, CustomStruct &R) {
+  ObjectMapper O(E);
+  if (!O || !O.map("str", R.S) || !O.map("int", R.I))
+    return false;
+  O.map("bool", R.B);
+  return true;
+}
+
+TEST(JSONTest, Deserialize) {
+  std::map<std::string, std::vector<CustomStruct>> R;
+  CustomStruct ExpectedStruct = {"foo", 42, true};
+  std::map<std::string, std::vector<CustomStruct>> Expected;
+  Value J = Object{
+      {"foo",
+       Array{
+           Object{
+               {"str", "foo"},
+               {"int", 42},
+               {"bool", true},
+               {"unknown", "ignored"},
+           },
+           Object{{"str", "bar"}},
+           Object{
+               {"str", "baz"}, {"bool", "string"}, // OK, deserialize ignores.
+           },
+       }}};
+  Expected["foo"] = {
+      CustomStruct("foo", 42, true),
+      CustomStruct("bar", llvm::None, false),
+      CustomStruct("baz", llvm::None, false),
+  };
+  ASSERT_TRUE(fromJSON(J, R));
+  EXPECT_EQ(R, Expected);
+
+  CustomStruct V;
+  EXPECT_FALSE(fromJSON(nullptr, V)) << "Not an object " << V;
+  EXPECT_FALSE(fromJSON(Object{}, V)) << "Missing required field " << V;
+  EXPECT_FALSE(fromJSON(Object{{"str", 1}}, V)) << "Wrong type " << V;
+  // Optional<T> must parse as the correct type if present.
+  EXPECT_FALSE(fromJSON(Object{{"str", 1}, {"int", "string"}}, V))
+      << "Wrong type for Optional<T> " << V;
+}
+
+} // namespace
+} // namespace json
+} // namespace llvm