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Merged
kripken merged 3 commits into from
May 14, 2026
+149 −25
Merged

JSON: Implement printing for all types #8701

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4b500a2
work
kripken May 14, 2026
7d01d88
c++20
kripken May 14, 2026
43f58d2
maybeNewline helper
kripken May 14, 2026
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93 changes: 71 additions & 22 deletions src/support/json.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -19,30 +19,79 @@

namespace json {

void Value::stringify(std::ostream& os, bool pretty) {
if (isString()) {
std::stringstream wtf16;
[[maybe_unused]] bool valid =
wasm::String::convertWTF8ToWTF16(wtf16, getIString().view());
assert(valid);
// TODO: Use wtf16.view() once we have C++20.
wasm::String::printEscapedJSON(os, wtf16.str());
} else if (isArray()) {
os << '[';
auto first = true;
for (auto& item : getArray()) {
if (first) {
first = false;
} else {
// TODO pretty whitespace
os << ',';
void Value::stringify(std::ostream& os, bool pretty, int indent) {
auto doIndent = [&]() {
for (int i = 0; i < indent; i++) {
os << ' ';
}
};

auto maybeNewline = [&]() {
if (pretty) {
os << '\n';
doIndent();
}
};

switch (type) {
case String: {
std::stringstream wtf16;
[[maybe_unused]] bool valid =
wasm::String::convertWTF8ToWTF16(wtf16, getIString().view());
assert(valid);
wasm::String::printEscapedJSON(os, wtf16.view());
return;
}
case Array: {
os << '[';
indent++;
auto first = true;
for (auto& item : getArray()) {
if (first) {
first = false;
} else {
os << ',';
}
maybeNewline();
item->stringify(os, pretty, indent);
}
indent--;
maybeNewline();
os << ']';
return;
}
case Object: {
os << '{';
indent++;
auto first = true;
for (auto& [key, value] : getObject()) {
if (first) {
first = false;
} else {
os << ',';
}
maybeNewline();
os << "\"" << key << "\":";
if (pretty) {
os << ' ';
}
value->stringify(os, pretty, indent);
}
item->stringify(os, pretty);
indent--;
maybeNewline();
os << '}';
return;
}
os << ']';
} else {
WASM_UNREACHABLE("TODO: stringify all of JSON");
}
case Number:
os << getNumber();
return;
case Null:
os << "null";
return;
case Bool:
os << (getBool() ? "true" : "false");
return;
};
}

} // namespace json
24 changes: 22 additions & 2 deletions src/support/json.h
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Expand Up @@ -37,6 +37,7 @@
#include <unordered_set>
#include <vector>

#include "support/insert_ordered.h"
#include "support/istring.h"
#include "support/safe_integer.h"
#include "support/string.h"
Expand Down Expand Up @@ -67,7 +68,18 @@ struct Value {
Ref& operator[](IString x) { return (*this->get())[x]; }
};

static Ref make() { return Ref(new Value); }
template<typename T> static Ref make(T t) { return Ref(new Value(t)); }
static Ref makeArray() {
Ref ret(new Value);
ret->setArray();
return ret;
}
static Ref makeObject() {
Ref ret(new Value);
ret->setObject();
return ret;
}

enum Type {
String = 0,
Expand All @@ -81,7 +93,7 @@ struct Value {
Type type = Null;

using ArrayStorage = std::vector<Ref>;
using ObjectStorage = std::unordered_map<IString, Ref>;
using ObjectStorage = wasm::InsertOrderedMap<IString, Ref>;

// MSVC does not allow unrestricted unions:
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2544.pdf
Expand All @@ -102,6 +114,10 @@ struct Value {
// constructors all copy their input
Value() {}
explicit Value(const char* s) : type(Null) { setString(s); }
explicit Value(const std::string& s) : type(Null) { setString(s.c_str()); }
explicit Value(const std::string_view& s) : type(Null) {
setString(std::string(s));
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@tlively tlively May 14, 2026

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Suggested change
setString(std::string(s));
setString(s.data());

This seems like it does the same thing a little more directly.

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@kripken kripken May 14, 2026

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Hmm, but the data is not null-terminated?

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@tlively tlively May 14, 2026

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Oh right. Never mind then.

}
explicit Value(double n) : type(Null) { setNumber(n); }
explicit Value(ArrayStorage& a) : type(Null) {
setArray();
Expand Down Expand Up @@ -202,6 +218,10 @@ struct Value {
assert(isArray());
return *arr;
}
ObjectStorage& getObject() {
assert(isObject());
return *obj;
}
bool& getBool() {
assert(isBool());
return boo;
Expand Down Expand Up @@ -378,7 +398,7 @@ struct Value {
return curr;
}

void stringify(std::ostream& os, bool pretty = false);
void stringify(std::ostream& os, bool pretty = false, int indent = 0);

// String operations

Expand Down
57 changes: 56 additions & 1 deletion test/gtest/json.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@

using JSONTest = ::testing::Test;

TEST_F(JSONTest, Stringify) {
TEST_F(JSONTest, RoundtripString) {
// TODO: change the API to not require a copy
auto input = "[\"hello\",\"world\"]";
auto* copy = strdup(input);
Expand All @@ -14,3 +14,58 @@ TEST_F(JSONTest, Stringify) {
EXPECT_EQ(ss.str(), input);
free(copy);
}

static void
checkOutput(json::Value::Ref ref, std::string expected, bool pretty = false) {
std::stringstream ss;
ref->stringify(ss, pretty);
EXPECT_EQ(ss.str(), expected);
}

static void checkPrettyOutput(json::Value::Ref ref, std::string expected) {
checkOutput(ref, expected, true);
}

TEST_F(JSONTest, StringifyArray) {
auto array = json::Value::makeArray();
array->push_back(json::Value::make(42));
array->push_back(json::Value::make("1337"));
array->push_back(json::Value::make()); // null
checkOutput(array, "[42,\"1337\",null]");
checkPrettyOutput(array, R"([
42,
"1337",
null
])");
}

TEST_F(JSONTest, StringifyObject) {
auto object = json::Value::makeObject();
object["foo"] = json::Value::make(42);
object["bar"] = json::Value::make("1337");
checkOutput(object, "{\"foo\":42,\"bar\":\"1337\"}");
checkPrettyOutput(object, R"({
"foo": 42,
"bar": "1337"
})");
}

TEST_F(JSONTest, StringifyNesting) {
auto array = json::Value::makeArray();
auto object = json::Value::makeObject();
auto array1 = json::Value::makeArray();
auto object1 = json::Value::makeObject();
array->push_back(object);
object["body"] = array1;
array1->push_back(object1);
object1["value"] = json::Value::make(42);
checkPrettyOutput(array, R"([
{
"body": [
{
"value": 42
}
]
}
])");
}
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