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Add JSON output support to Emboss text format #237

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36 changes: 29 additions & 7 deletions compiler/back_end/cpp/generated_code_templates
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Original file line number Diff line number Diff line change
Expand Up @@ -296,11 +296,18 @@ ${write_fields}
// Avoid unused variable warnings for empty structures:
(void)emboss_reserved_local_wrote_field;
if (emboss_reserved_local_options.multiline()) {
if (emboss_reserved_local_wrote_field &&
emboss_reserved_local_options.json()) {

@reventlov reventlov Dec 3, 2025

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You can delete the && ...json() here and then lines 348-351 entirely, I believe.

@AaronWebster AaronWebster Jun 3, 2026

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That would break non-JSON multiline output, suggestion?

emboss_reserved_local_stream->Write("\n");
}
emboss_reserved_local_stream->Write(
emboss_reserved_local_options.current_indent());
emboss_reserved_local_stream->Write("}");
} else {
emboss_reserved_local_stream->Write(" }");
if (!emboss_reserved_local_options.json()) {
emboss_reserved_local_stream->Write(" ");
}
emboss_reserved_local_stream->Write("}");
}
}

Expand All @@ -324,20 +331,35 @@ ${write_fields}
// they are not `Ok()` overall, since submembers may still be `Ok()`.
if (!emboss_reserved_local_field_options.allow_partial_output() ||
${field_name}().IsAggregate() || ${field_name}().Ok()) {
if (emboss_reserved_local_wrote_field) {
if (emboss_reserved_local_field_options.json() ||
!emboss_reserved_local_field_options.multiline()) {
emboss_reserved_local_stream->Write(",");
}
}
if (emboss_reserved_local_field_options.multiline()) {
// In JSON mode, each field goes on its own line, so emit the newline
// that separates this field from the previous one. (In non-JSON
// mode the previous field already wrote its own trailing newline.)
if (emboss_reserved_local_wrote_field &&
emboss_reserved_local_field_options.json()) {
emboss_reserved_local_stream->Write("\n");
}
emboss_reserved_local_stream->Write(
emboss_reserved_local_field_options.current_indent());
} else {
if (emboss_reserved_local_wrote_field) {
emboss_reserved_local_stream->Write(",");
}
} else if (!emboss_reserved_local_field_options.json()) {
emboss_reserved_local_stream->Write(" ");
}
emboss_reserved_local_stream->Write("${field_name}: ");
if (emboss_reserved_local_field_options.json()) {
emboss_reserved_local_stream->Write("\"${field_name}\":");
} else {
emboss_reserved_local_stream->Write("${field_name}: ");
}
${field_name}().WriteToTextStream(emboss_reserved_local_stream,
emboss_reserved_local_field_options);
emboss_reserved_local_wrote_field = true;
if (emboss_reserved_local_field_options.multiline()) {
if (emboss_reserved_local_field_options.multiline() &&
!emboss_reserved_local_field_options.json()) {
emboss_reserved_local_stream->Write("\n");
}
} else if (emboss_reserved_local_field_options.allow_partial_output() &&
Expand Down
128 changes: 125 additions & 3 deletions compiler/back_end/cpp/testcode/text_format_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -15,11 +15,11 @@
// Tests of generated code for text format.
#include <stdint.h>

#include <type_traits>
#include <utility>
#include <vector>
#include <array>
#include <numeric>

#include "gtest/gtest.h"
#include "runtime/cpp/emboss_text_util.h"
#include "testdata/text_format.emb.h"

namespace emboss {
Expand Down Expand Up @@ -93,6 +93,128 @@ TEST(TextFormat, UpdateFromText) {
EXPECT_EQ(view.b().Read(), 4);
}

TEST(TextFormat, JsonOutput) {
::std::array<char, 57> values = {};
::std::iota(values.begin(), values.end(), 0);

const auto view = MakeJsonTestStructView(&values);
EXPECT_EQ(
"{\"one_byte_enum\":\"ZERO\",\"seven_bit_uint\":1,\"one_bit_flag\":"
"false,\"one_byte_uint\":2,\"two_byte_uint\":1027,"
"\"four_byte_uint\":134678021,\"eight_byte_uint\":"
"1157159078456920585,\"uint8_array\":[17,18,19,20,21,22,23,24,"
"25,26],\"uint16_array\":[7195,7709,8223,8737,9251,9765,10279,"
"10793,11307,11821],\"struct_array\":[{\"element_one\":47,"
"\"element_two\":48,\"element_three\":49,\"element_four\":50},"
"{\"element_one\":51,\"element_two\":52,\"element_three\":53,"
"\"element_four\":54}]}",
::emboss::WriteToString(view, TextOutputOptions().Json(true)));
}

TEST(TextFormat, JsonMultilineOutput) {
::std::array<char, 3> values = {1, 2, 3};
const auto view = MakeStructWithSkippedFieldsView(&values);
// In multiline JSON mode, each field is written on its own indented line,
// separated by commas, with the closing brace on its own line.
EXPECT_EQ(
"{\n"
" \"a\":1,\n"
" \"c\":3\n"
"}",
::emboss::WriteToString(
view,
TextOutputOptions().Json(true).Multiline(true).WithIndent(" ")));
}

TEST(TextFormat, JsonOutputRobustness) {
::std::array<char, 57> values = {};
::std::iota(values.begin(), values.end(), 0);

const auto view = MakeJsonTestStructView(&values);
auto options = ::emboss::TextOutputOptions()
.Json(true)
.WithComments(true)
.WithDigitGrouping(true)
.WithNumericBase(16);
EXPECT_EQ(
"{\"one_byte_enum\":\"ZERO\",\"seven_bit_uint\":1,\"one_bit_flag\":"
"false,\"one_byte_uint\":2,\"two_byte_uint\":1027,"
"\"four_byte_uint\":134678021,\"eight_byte_uint\":"
"1157159078456920585,\"uint8_array\":[17,18,19,20,21,22,23,24,"
"25,26],\"uint16_array\":[7195,7709,8223,8737,9251,9765,10279,"
"10793,11307,11821],\"struct_array\":[{\"element_one\":47,"
"\"element_two\":48,\"element_three\":49,\"element_four\":50},"
"{\"element_one\":51,\"element_two\":52,\"element_three\":53,"
"\"element_four\":54}]}",
::emboss::WriteToString(view, options));
}

TEST(TextFormat, DigitGroupingAndNumericBase) {
::std::array<char, 57> values = {};
::std::iota(values.begin(), values.end(), 0);

const auto view = MakeJsonTestStructView(&values);
auto options =
::emboss::TextOutputOptions().WithDigitGrouping(true).WithNumericBase(16);
EXPECT_EQ(
"{ one_byte_enum: ZERO, seven_bit_uint: 0x1, one_bit_flag: false, "
"one_byte_uint: 0x2, two_byte_uint: 0x403, four_byte_uint: 0x807_0605, "
"eight_byte_uint: 0x100f_0e0d_0c0b_0a09, uint8_array: { [0x0]: 0x11, "
"0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, [0x8]: 0x19, 0x1a }, "
"uint16_array: { [0x0]: 0x1c1b, 0x1e1d, 0x201f, 0x2221, 0x2423, 0x2625, "
"0x2827, 0x2a29, [0x8]: 0x2c2b, 0x2e2d }, struct_array: { [0x0]: { "
"element_one: 0x2f, element_two: 0x30, element_three: 0x31, "
"element_four: 0x32 }, { element_one: 0x33, element_two: 0x34, "
"element_three: 0x35, element_four: 0x36 } } }",
::emboss::WriteToString(view, options));
}

TEST(TextFormat, MultilineAndPartial) {
::std::array<char, 1> values = {10};
// MakeVanillaView expects a pointer to an array of size 2, so we have to
// construct the view manually.
auto view = VanillaWriter(values.data(), values.size());
auto options =
::emboss::TextOutputOptions().Multiline(true).WithAllowPartialOutput(
true);
EXPECT_EQ(
"{\n"
"a: 10\n"
"}",
::emboss::WriteToString(view, options));
}

TEST(TextFormat, JsonSkippedFieldOutput) {
::std::array<char, 3> values = {1, 2, 3};
const auto view = MakeStructWithSkippedFieldsView(&values);
EXPECT_EQ("{\"a\":1,\"c\":3}",
::emboss::WriteToString(view, TextOutputOptions().Json(true)));
}

TEST(TextFormat, JsonLargeIntegerAsString) {
::std::array<char, 57> values = {};
::std::iota(values.begin(), values.end(), 0);

const auto view = MakeJsonTestStructView(&values);
auto options = ::emboss::TextOutputOptions()
.Json(true)
.WithJsonLargeIntegerHandling(
JsonLargeIntegerHandling::kLargeAsString);
// With kLargeAsString, the eight_byte_uint should be quoted, but smaller
// integers should remain as numbers.
EXPECT_EQ(
"{\"one_byte_enum\":\"ZERO\",\"seven_bit_uint\":1,\"one_bit_flag\":"
"false,\"one_byte_uint\":2,\"two_byte_uint\":1027,"
"\"four_byte_uint\":134678021,\"eight_byte_uint\":"
"\"1157159078456920585\",\"uint8_array\":[17,18,19,20,21,22,23,24,"
"25,26],\"uint16_array\":[7195,7709,8223,8737,9251,9765,10279,"
"10793,11307,11821],\"struct_array\":[{\"element_one\":47,"
"\"element_two\":48,\"element_three\":49,\"element_four\":50},"
"{\"element_one\":51,\"element_two\":52,\"element_three\":53,"
"\"element_four\":54}]}",
::emboss::WriteToString(view, options));
}

} // namespace
} // namespace test
} // namespace emboss
2 changes: 1 addition & 1 deletion compiler/util/parser_types.py
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@
"""Types related to the LR(1) parser.

This module contains types used by the LR(1) parser, which are also used in
other parts of the compiler:
other parts of the compiler:

SourcePosition: a position (zero-width) within a source file.
SourceLocation: a span within a source file.
Expand Down
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