Simplify the implementation by reducing the number of branches.
Change-Id: I6e2ffee0fc2d77f7e2a70f76e03d081f4fc0e99d
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/247459
Reviewed-by: Herbie Ong <herbie@google.com>
This CL adds runtime support for unknown fields to be represented
as *[]byte in addition to the current representation as []byte.
This CL does not change generated code to use *[]byte.
Comparison between using *[]byte and []byte:
• Every message supports unknown fields, so use of []byte
expands a message size by 24B (for 64-bit systems).
In contrast, *[]byte only expands a message by 8B.
This has significant memory implications for small messages.
• If unknown fields are encountered, *[]byte has extra overhead
allocating the 24B slice header. However, it is assumed
that messages rarely see any unknown fields at runtime,
or generally do so for a temporary period of time.
Change-Id: I81935e4ea7394166e61ff4579f76f59fa792dfc9
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/244937
Reviewed-by: Damien Neil <dneil@google.com>
This variable is only used by the aberrantMessage type,
rename it to properly reflect what it is used for.
Change-Id: I081e8954eb1b282f01f6d2d764bffaf31c6677e9
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/245077
Reviewed-by: Damien Neil <dneil@google.com>
The MessageName returns the full name of a message.
It is a shorthand for:
var name protoreflect.FullName
if m != nil {
name = m.ProtoReflect().Descriptor().FullName()
}
Generally, we avoid the addition of helper functions unless
their use is justified. Arguments for this helper:
• The legacy proto.MessageName is widely used.
For example, inside Google, there are thousands of usages of it.
It is commonly used in logging and error construction to
report the name of a protobuf message.
• The fact that a nil-check may be neccessary means that users
either forget the nil-check and risk a nil-panic in production code,
or users have to write cumbersome logic to check for it.
For example, compare use with the helper:
return fmt.Errorf("invalid message type: %v", proto.MessageName(m))
to use without the helper:
var messageName protoreflect.FullName
if m != nil {
messageName = m.ProtoReflect().Descriptor().FullName()
}
return fmt.Errorf("invalid message type: %v", messageName)
A point of consideration is whether this should return a string
or a protoreflect.FullName. This CL returns the latter type:
• Most uses of it are for logging via log.Printf or error construction
via fmt.Errorf where it does not matter what the exact string type is
since its formatted the same way.
• Another use of it is to check for message type equality by doing
something similar to:
if proto.MessageName(got) != proto.MessageName(want) {
...
}
in which case it still does not matter what the exact string type is.
• The other major use of proto.MessageName is to call proto APIs
that actually do expect a protoreflect.FullName
(e.g., protoregistry.GlobalTypes.FindExtensionByNumber) where
the user currently type-casts the legacy proto.MessageName
to a protoreflect.FullName anyways.
As such, there does not seem to be much justified use for MessageName
as a string. The rare cases that need a string can trivially type cast
it to a string.
Change-Id: I840758df828eef72e7e63620569363a496366afa
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/242377
Reviewed-by: Damien Neil <dneil@google.com>
Added API:
SourceLocations.ByPath
SourceLocations.ByDescriptor
SourceLocation.Next
SourcePath.String
SourcePath.Equal
We modify compiler/protogen to use SourceLocations.ByDescriptor.
In retrospect, if this had existed during the development of protogen,
we would not have exposed protogen.Location and related fields.
Change-Id: I58f17e59f90b9ba16f0982c4b71c2542e4ff6e75
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/238000
Reviewed-by: Damien Neil <dneil@google.com>
The MessageFieldTypes interface (if implemented by a MessageType)
provides Go type information about the fields if they are
an enum or message type.
Change-Id: I68b20f5726377f6b0f2c20a8b6e45f9802b43f67
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/236777
Reviewed-by: Damien Neil <dneil@google.com>
When proto.Unmarshal fails, it is almost always due to being passed
input which is not a wire-format message. (A text-format message, a
message with framing left intact, and so forth.) An error like
"variable length integer overflow" can be confusing in this case, since
it implies the problem is the varint rather than the input being
entirely wrong.
Replace all Unmarshal parse errors with "cannot parse invalid
wire-format data".
Change-Id: Id97253bd39ac604e569df71778194f37b3c86c28
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/244297
Reviewed-by: Joe Tsai <joetsai@google.com>
In order for the synthetic @type field to potentially get reordered,
we implement insertion of that synthetic field by adding it
as a synthetic field that Range may iterate over.
This change sets up this code to more readily support a
hypothetical serialization mode for canonical serialization.
Change-Id: Ia0015a1a0804c15805dc5f3a3511fcf0f8513418
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/243817
Reviewed-by: Herbie Ong <herbie@google.com>
MessageSet are a proto1 feature only used by Google.
We no longer rely on the name mangling logic performed here,
so remove it.
Change-Id: I5d66ebd86875894632f0d0c1e9816ae47ee0d5f4
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/242657
Reviewed-by: Herbie Ong <herbie@google.com>
We should use TextName instead of Name,
since it is the name that actually appears in the .proto file.
Change-Id: Ie526b200d18b0994d93dbb347c266fa5c50cddfe
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/241658
Reviewed-by: Herbie Ong <herbie@google.com>
Add a new TextName accessor that returns the field name that should
be used for the text format. It is usually just the field name, except:
1) it uses the inlined message name for groups,
2) uses the full name surrounded by brackets for extensions, and
3) strips the "message_set_extension" for well-formed extensions
to the proto1 MessageSet.
We make similar adjustments to the JSONName accessor so that it applies
similar semantics for extensions.
The two changes simplifies all logic that wants the humanly readable
name for a field.
Change-Id: I524b6e017fb955146db81819270fe197f8f97980
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/239838
Reviewed-by: Herbie Ong <herbie@google.com>
Fix the tests to work on GOARCH=386.
Also add another test suite that tests on GOARCH=386.
Change-Id: I41290998053dc059347adb8af70012dc5cc31811
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/241537
Reviewed-by: Herbie Ong <herbie@google.com>
Profiling shows FindMessageByName spending considerable time
in strings.LastIndexByte in FindMessageByURL.
This overhead can be avoided by giving FindMessageByName
its own implementation not pruning the name string up
to the last '/' which can not appear in a protobuf name.
Change-Id: Ifec07689f72790ead8b7552cd04dd99fa67b61e4
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/240378
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
The order package replaces the mapsort and fieldsort packages.
It presents a common API for ordered iteration over message fields
and map fields.
It has a number of pre-defined orderings.
Change-Id: Ie6cd423da30b4757864c352cb04454f21fe07ee2
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/239837
Reviewed-by: Herbie Ong <herbie@google.com>
Centralize the MessageSet extension resolution logic in the registry.
This avoids needless replication of this exact logic in multiple places
(for JSON and text) and elsewhere.
Change-Id: I70bfea899e295e8c589f418965bf0dd099f93628
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/240077
Reviewed-by: Herbie Ong <herbie@google.com>
This adds the use of the staticcheck tool to check our code.
The use of staticcheck would have caught a bug in CL/211737.
Also, we adjust one minor code patterns to avoid triggering
one of the staticcheck checks.
This CL also modifies the integration script to check SHA256
checksums for archives downloaded from a third-party source.
Change-Id: Ieb69ae79464de62970448195c77cdd88e21fc48f
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/212220
Reviewed-by: Damien Neil <dneil@google.com>
Trivial adjustments to error handling to reduce differences between
the generated helpers and the legacy ptypes package.
Change-Id: Ib3022eb50d9a9c0906b7809fe7e8011ee9399b0a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/238009
Reviewed-by: Damien Neil <dneil@google.com>
Many usages of the legacy ptypes.Timestamp and ptypes.Duration rely
on the functions implicitly returning an error for a nil message.
In order to migrate previous usages of the ptypes constructors to
the new API, we modify CheckValid to preserve similar semantics.
There is some consistency with this change in that:
(*M)(nil).IsValid() == (*M)(nil).ProtoReflect().IsValid()
where M is Duration, Timestamp, and FieldMask.
Change-Id: I05ae152511f9875ea034e78aefb7aab18d17a318
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/238007
Reviewed-by: Damien Neil <dneil@google.com>
For simplicity, IsValid was implemented in terms of regular expressions,
which are useful for verifying a string according to a strict grammar,
but performs poorly. Implement the check in terms of hand-written code,
which provides a 20x improvement to validate the name "google.protobuf.Any".
name old time/op new time/op delta
FullNameIsValid-8 683ns ± 2% 35ns ± 1% -94.86% (p=0.000 n=10+10)
Change-Id: I980403befca0b72cea22acd274064a46cb02644b
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/238002
Reviewed-by: Damien Neil <dneil@google.com>
While the MarshalFrom method and function are more flexible since
it permits the reuse of an existing Any, the most common use case
by far is to construct a new Any. Optimize for that use case
by providing a constructor that directly returns a new Any instance.
We do not provide a variant that accepts a MarshalOptions since
the more flexible MarshalFrom function can be used for that.
Change-Id: Iab0219229c7d3aaa7390a2340a4f248002995293
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/237997
Reviewed-by: Damien Neil <dneil@google.com>
Add checks so that MarshalFrom and UnmarshalTo consistently matches
the behavior of the proto package with regard to nil messages.
In particular, using a nil message as the destination results in
a panic (which is already the current behavior), while using a
nil message as the source does not panic (it is usually treated as
an untyped empty message). Since an untyped message has no
sensible meaning in the context of Any, return an error.
Change-Id: I99e86c2cdfbd8be57cc039efd550458dc56aadbc
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/237920
Reviewed-by: Damien Neil <dneil@google.com>
For marshaling, apart from already existing check that each item in
paths field is reversible, also make sure that string is a valid
protobuf name.
For unmarshaling, make sure that each resulting item in paths field is
a valid protobuf name and input path item does not contain _. The latter
check satisfies the conformance test
Recommended.Proto3.JsonInput.FieldMaskInvalidCharacter.
Fixesgolang/protobuf#1141.
Change-Id: Iffc278089b20e496b7216d5b8c966b21b70e782d
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/236998
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Add support for creating dynamic EnumTypes.
Change-Id: Ic9f5b73630734848b29cc436f6c179549a8ea74a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/237219
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Reviewed-by: Joe Tsai <joetsai@google.com>
This CL introduces generation of specialized APIs directly into the
generated packages for certain well-known types. This follows the pattern
set forth by the other language implementations that have specialized
generated support for certain well-known types.
Overview of new API:
package anypb
func MarshalFrom(*Any, proto.Message, proto.MarshalOptions) error
func UnmarshalTo(*Any, proto.Message, proto.UnmarshalOptions) error
func UnmarshalNew(*Any, proto.UnmarshalOptions) (proto.Message, error)
func (*Any) MessageIs(proto.Message) bool
func (*Any) MessageName() protoreflect.FullName
func (*Any) MarshalFrom(proto.Message) error
func (*Any) UnmarshalTo(proto.Message) error
func (*Any) UnmarshalNew() (proto.Message, error)
package timestamppb
func Now() *Timestamp
func New(time.Time) *Timestamp
func (*Timestamp) AsTime() time.Time
func (*Timestamp) IsValid() bool
func (*Timestamp) CheckValid() error
package durationpb
func New(time.Duration) *Duration
func (*Duration) AsDuration() time.Duration
func (*Duration) IsValid() bool
func (*Duration) CheckValid() error
package structpb
func NewStruct(map[string]interface{}) (*Struct, error)
func (*Struct) AsMap() map[string]interface{}
func (*Struct) MarshalJSON() ([]byte, error)
func (*Struct) UnmarshalJSON(b []byte) error
func NewList([]interface{}) (*ListValue, error)
func (*ListValue) AsSlice() []interface{}
func (*ListValue) MarshalJSON() ([]byte, error)
func (*ListValue) UnmarshalJSON(b []byte) error
func NewValue(interface{}) (*Value, error)
func NewNullValue() *Value
func NewBoolValue(bool) *Value
func NewNumberValue(float64) *Value
func NewStringValue(string) *Value
func NewStructValue(*Struct) *Value
func NewListValue(*ListValue) *Value
func (*Value) AsInterface() interface{}
func (*Value) MarshalJSON() ([]byte, error)
func (*Value) UnmarshalJSON(b []byte) error
package fieldmaskpb
func New(proto.Message, ...string) (*FieldMask, error)
func Union(*FieldMask, *FieldMask, ...*FieldMask) *FieldMask
func Intersect(*FieldMask, *FieldMask, ...*FieldMask) *FieldMask
func (*FieldMask) IsValid(proto.Message) bool
func (*FieldMask) Append(proto.Message, ...string) error
func (*FieldMask) Normalize()
package wrapperspb
func Bool(bool) *BoolValue
func Int32(int32) *Int32Value
func Int64(int64) *Int64Value
func UInt32(uint32) *UInt32Value
func UInt64(uint64) *UInt64Value
func Float(float32) *FloatValue
func Double(float64) *DoubleValue
func String(string) *StringValue
func Bytes([]byte) *BytesValue
This functionality expands upon and supersedes the
older github.com/golang/protobuf/ptypes package,
which provided helpers for Any, Timestamp, and Duration.
Comparison with older ptypes package:
* ptypes.AnyMessageName is replaced by anypb.Any.MessageName.
The former returned an error for malformed type URLs,
while the latter simply returns an empty string.
* ptypes.Is is replaced by anypb.Any.MessageIs.
* ptypes.Empty has no direct replacement as it is equivalent to:
mt, err := protoregistry.GlobalTypes.FindMessageByURL(any.GetTypeUrl())
if err != nil {
return nil, err
}
return mt.New().Interface(), nil
Analysis of user code revealed that this function is seldom used.
* ptypes.MarshalAny is replaced by anypb.Any.MarshalFrom.
The former creates a new Any message and returns it,
while the latter is a method that modifies the receiver.
* ptypes.UnmarshalAny is replaced by anypb.Any.UnmarshalTo.
* ptypes.DynamicAny is loosely replaced by anypb.Any.UnmarshalNew.
The DynamicAny type is a custom proto.Message that is special
to ptypes.UnmarshalAny where it would allocate a new message
and store it into the DynamicAny instance. The UnmarshalNew method
accomplishes the equivalent functionality in a more direct fashion.
* ptypes.TimestampNow is replaced by timestamppb.Now.
* ptypes.TimestampProto is replaced by timestamppb.New.
The former returned an error if the timestamp was outside the
10000-year range recommended by timestamp.proto,
while the latter always succeeded. To preserve the behavior of
the former validation check, the replacement can additionally
call the timestamppb.Timestamp.CheckValid method.
* ptypes.Timestamp is replaced by timestamppb.Timestamp.AsTime.
The former returned an error if the timestamp was outside the
10000-year range recommended by timestamp.proto,
while the latter always succeeded. To preserve the behavior of
the former validation check, the replacement can additionally
call the timestamppb.Timestamp.CheckValid method.
* ptypes.TimestampString has no direct replacement as it is equivalent to:
ts.AsTime().Format(time.RFC3339Nano)
* ptypes.DurationProto is replaced by durationpb.New.
* ptypes.Duration is replaced by durationpb.Duration.AsDuration.
The former returned an error if the duration would overflow
when converting to a time.Duration, while the latter uses
saturation arithmetic (similiar to the time package itself).
Underflow resulted in time.Duration(math.MinInt64), while
overflow resulted in time.Duration(math.MaxInt64).
To preserve the behavior of former validation checks,
the replacement can call the durationpb.Duration.CheckValid method
and check whether the duration is fixed to one of the overflow values.
Change-Id: Ia996b1037a1fcafced7c7e10e9408ef7fa22863a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/225298
Reviewed-by: Damien Neil <dneil@google.com>
It seems safer to explicitly mention exactly which messages
have special handling, rather than special casing the .profile
that they live in. This is safer because there is no guarantee
that new messages won't be added to each of these files.
The protojson implementation is modified to no longer rely
on a isCustomType helper and instead return a marshal or unmarshal
function pointer that is non-nil if specialized serialization
exists for that message type.
Change-Id: I5e3551d66f5a4b9024e583b627c0292cb7da6803
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/235657
Reviewed-by: Herbie Ong <herbie@google.com>
Identify well-known types by message name instead of the .proto file
that they belong to in case more are added (however unlikely).
Change-Id: I77b8880c106960b0d9a1cb304e2990e1bcddeb39
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/235478
Reviewed-by: Herbie Ong <herbie@google.com>
The genid package unifies the genname, fieldnum, and detectknown
packages into a single package.
Whenever possible use the generated constants rather than
hard-coded literals. This makes it easier to search the entire
module for special logic that deal with well-known types.
Change-Id: I13beff1f4149444a0c0b9e607ebf759657f000f4
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/235301
Reviewed-by: Herbie Ong <herbie@google.com>
A hasFields map that only ever contains 3 entries seems more
complex than necessary. It's simpler and more performant to
just track three discrete boolean variables for each of the cases.
Change-Id: I1ba20da130f6b560a57fe8c3a73968983e563b48
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/235477
Reviewed-by: Herbie Ong <herbie@google.com>
A common mistake is to pass proto.Message to protoreflect.ValueOf
instead of a protoreflect.Message. Specialize for this case
and provide a panic message that is more helpful.
Change-Id: I5def43341aa9607182edde309dea2823e61c1fdb
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/234117
Reviewed-by: Damien Neil <dneil@google.com>
This is step 4 of 6 in a multi-stage migration
to move the well-known types
from the google.golang.org/genproto module
to the google.golang.org/protobuf module.
The generated Go packages for field_mask.proto, api.proto,
type.proto, and source_context.proto are being moved over
to this module alongside all the other well-known types.
In order to move these types between two modules,
there needs to be a sequence of changes submitted in
decently rapid succession. It is impossible to atomically
make these changes, so a brief breakage is inevitable.
The steps are as follows:
Step 1: Submit a change to cloud.google.com/go/internal/gapicgen
to avoid generating the well-known types. Otherwise, the tool
will undo the changes made in step 3.
See https://code-review.googlesource.com/c/gocloud/+/56810
Step 2: Submit a change to google.golang.org/protobuf that
adds the generated well-known types being migrated to that module.
In order to prevent the situation where a user links in
too old a version of the genproto module such that
duplicate registration occurs for the well-known types,
the registry is specially modified to provide an error
message that instructs users to upgrade the genproto module.
See https://golang.org/cl/234937
Step 3: Submit a change to google.golang.org/genproto that
switches all generated well-known types to be aliases to the
ones declared in google.golang.org/protobuf from the previous step.
This will cause the genproto module to incur an dependency
on an unreleased version of the protobuf module.
See https://github.com/googleapis/go-genproto/pull/372
Step 4: Submit a change to google.golang.org/protobuf that
adds a weak module depdency on the genproto module at the
revision from the previous step.
See https://golang.org/cl/235297
Step 5: Release google.golang.org/protobuf@v1.24.0.
See https://golang.org/cl/235299
Step 6: Submit a change to google.golang.org/genproto that
updates the protobuf module dependency to v1.24.0.
Change-Id: I22d496e7496446becad742eab05b169abb735ae2
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/235297
Reviewed-by: Damien Neil <dneil@google.com>
This is step 2 of 6 in a multi-stage migration
to move the well-known types
from the google.golang.org/genproto module
to the google.golang.org/protobuf module.
The generated Go packages for field_mask.proto, api.proto,
type.proto, and source_context.proto are being moved over
to this module alongside all the other well-known types.
In order to move these types between two modules,
there needs to be a sequence of changes submitted in
decently rapid succession. It is impossible to atomically
make these changes, so a brief breakage is inevitable.
The steps are as follows:
Step 1: Submit a change to cloud.google.com/go/internal/gapicgen
to avoid generating the well-known types. Otherwise, the tool
will undo the changes made in step 3.
See https://code-review.googlesource.com/c/gocloud/+/56810
Step 2: Submit a change to google.golang.org/protobuf that
adds the generated well-known types being migrated to that module.
In order to prevent the situation where a user links in
too old a version of the genproto module such that
duplicate registration occurs for the well-known types,
the registry is specially modified to provide an error
message that instructs users to upgrade the genproto module.
See https://golang.org/cl/234937
Step 3: Submit a change to google.golang.org/genproto that
switches all generated well-known types to be aliases to the
ones declared in google.golang.org/protobuf from the previous step.
This will cause the genproto module to incur an dependency
on an unreleased version of the protobuf module.
See https://github.com/googleapis/go-genproto/pull/372
Step 4: Submit a change to google.golang.org/protobuf that
adds a weak module depdency on the genproto module at the
revision from the previous step.
Step 5: Release google.golang.org/protobuf@v1.24.0.
Step 6: Submit a change to google.golang.org/genproto that
updates the protobuf module dependency to v1.24.0.
Change-Id: I36a19049d2240b67a37dfad20e154505aee7c784
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/234937
Reviewed-by: Damien Neil <dneil@google.com>
Some companies (e.g., Google) run a profiling service where they may
choose to special-case certain symbols in a binary to classify
commonly used libraries like protobufs.
This CL funnels similar functionality through a single function
so that they can be more easily identified. This is by no means a
firm statement that these identifiers will never change names,
but at least the code documents warnings to avoid changing the
name of certain identifiers.
This CL provides the following semi-stable symbol names:
"google.golang.org/protobuf/proto".MarshalOptions.size
"google.golang.org/protobuf/proto".MarshalOptions.marshal
"google.golang.org/protobuf/proto".UnmarshalOptions.unmarshal
"google.golang.org/protobuf/encoding/prototext".MarshalOptions.marshal
"google.golang.org/protobuf/encoding/prototext".UnmarshalOptions.unmarshal
"google.golang.org/protobuf/encoding/protojson".MarshalOptions.marshal
"google.golang.org/protobuf/encoding/protojson".UnmarshalOptions.unmarshal
Merge and Clone are not part of the above set since there is a
possibility that MergeOptions will be added in the future.
We use an unexported method so that we have the freedom to change the
method however we want since profilers do not care about that.
Change-Id: Ia79af260d00125f48139420e1e18a86482bd1829
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/234079
Reviewed-by: Damien Neil <dneil@google.com>
The following changes are made:
* Permit invalid UTF-8 in proto2. This goes against specified behavior,
but matches functional behavior in wire marshaling (not just for Go,
but also in the other major language implementations as well).
* The Format function is specified as ignoring errors since its intended
purpose is to surface information to the human user even if it's not
exactly parsible back into a message. As such, add an unexported
allowInvalidUTF8 option that is specially used by Format.
* Add an EmitASCII option that forces the formatting of
strings and bytes to always be encoded as ASCII.
This ensures that the entire output is always ASCII as well.
Note that we do not replicate this behavior for protojson since:
* The JSON format fundamentally has a stricter and well-specified
grammar for exactly what is valid/invalid, while the text format
has not had a well-specified grammar for the longest time,
leading to all sorts of weird usages due to Hyrum's law.
* This is to ease migration from the legacy implementation,
which did permit invalid UTF-8 in proto2.
* The EmitASCII option relies on the ability to always escape
Unicode characters using ASCII escape sequences, but this is not
possible in JSON since the grammar only has an escape sequence defined
for Unicode characters \u0000 to \uffff, inclusive.
However, Unicode v12.0.0 defines characters up to \U0010FFFF,
which is beyond what the JSON grammar provides escape sequences for.
Change-Id: I2b524a904e9ec59f9ed5500e299613bc27c31a14
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/233077
Reviewed-by: Herbie Ong <herbie@google.com>
