Merge pull request #3522 from SebastianKeller/WriteJson

Added 'writeJson' to write_stream.zig:

lib/std/json.zig

@@ -1407,6 +1407,7 @@ test "json.parser.dynamic" {
 
 test "import more json tests" {
     _ = @import("json/test.zig");
+    _ = @import("json/write_stream.zig");
 }
 
 test "write json then parse it" {

lib/std/json/write_stream.zig

@@ -197,6 +197,34 @@ pub fn WriteStream(comptime OutStream: type, comptime max_depth: usize) type {
             try self.stream.writeByte('"');
         }
 
+        /// Writes the complete json into the output stream
+        pub fn emitJson(self: *Self, json: std.json.Value) Stream.Error!void {
+            switch (json) {
+                .Null => try self.emitNull(),
+                .Bool => |inner| try self.emitBool(inner),
+                .Integer => |inner| try self.emitNumber(inner),
+                .Float => |inner| try self.emitNumber(inner),
+                .String => |inner| try self.emitString(inner),
+                .Array => |inner| {
+                    try self.beginArray();
+                    for (inner.toSliceConst()) |elem| {
+                        try self.arrayElem();
+                        try self.emitJson(elem);
+                    }
+                    try self.endArray();
+                },
+                .Object => |inner| {
+                    try self.beginObject();
+                    var it = inner.iterator();
+                    while (it.next()) |entry| {
+                        try self.objectField(entry.key);
+                        try self.emitJson(entry.value);
+                    }
+                    try self.endObject();
+                },
+            }
+        }
+
         fn indent(self: *Self) !void {
             assert(self.state_index >= 1);
             try self.stream.write(self.newline);
@@ -216,3 +244,61 @@ pub fn WriteStream(comptime OutStream: type, comptime max_depth: usize) type {
         }
     };
 }
+
+test "json write stream" {
+    var out_buf: [1024]u8 = undefined;
+    var slice_stream = std.io.SliceOutStream.init(&out_buf);
+    const out = &slice_stream.stream;
+
+    var mem_buf: [1024 * 10]u8 = undefined;
+    const allocator = &std.heap.FixedBufferAllocator.init(&mem_buf).allocator;
+
+    var w = std.json.WriteStream(@typeOf(out).Child, 10).init(out);
+    try w.emitJson(try getJson(allocator));
+
+    const result = slice_stream.getWritten();
+    const expected =
+        \\{
+        \\ "object": {
+        \\  "one": 1,
+        \\  "two": 2.0e+00
+        \\ },
+        \\ "string": "This is a string",
+        \\ "array": [
+        \\  "Another string",
+        \\  1,
+        \\  3.14e+00
+        \\ ],
+        \\ "int": 10,
+        \\ "float": 3.14e+00
+        \\}
+    ;
+    std.testing.expect(std.mem.eql(u8, expected, result));
+}
+
+fn getJson(allocator: *std.mem.Allocator) !std.json.Value {
+    var value = std.json.Value{ .Object = std.json.ObjectMap.init(allocator) };
+    _ = try value.Object.put("string", std.json.Value{ .String = "This is a string" });
+    _ = try value.Object.put("int", std.json.Value{ .Integer = @intCast(i64, 10) });
+    _ = try value.Object.put("float", std.json.Value{ .Float = 3.14 });
+    _ = try value.Object.put("array", try getJsonArray(allocator));
+    _ = try value.Object.put("object", try getJsonObject(allocator));
+    return value;
+}
+
+fn getJsonObject(allocator: *std.mem.Allocator) !std.json.Value {
+    var value = std.json.Value{ .Object = std.json.ObjectMap.init(allocator) };
+    _ = try value.Object.put("one", std.json.Value{ .Integer = @intCast(i64, 1) });
+    _ = try value.Object.put("two", std.json.Value{ .Float = 2.0 });
+    return value;
+}
+
+fn getJsonArray(allocator: *std.mem.Allocator) !std.json.Value {
+    var value = std.json.Value{ .Array = std.json.Array.init(allocator) };
+    var array = &value.Array;
+    _ = try array.append(std.json.Value{ .String = "Another string" });
+    _ = try array.append(std.json.Value{ .Integer = @intCast(i64, 1) });
+    _ = try array.append(std.json.Value{ .Float = 3.14 });
+
+    return value;
+}