I think the way to do it is just to create a new, separate double field and migrate over to that new field. Depending on how your message is used, you might have to temporarily populate both fields until all readers have been updated to prefer the new field.
On Thu, Nov 16, 2017 at 1:35 PM, James Philbin <philb...@gmail.com> wrote: > OK, thanks. Is there a recommended way of upgrading a float field to a > double field? There is no discussion of this path right now in the protobuf > docs. > > James > > On Thursday, November 16, 2017 at 11:16:58 AM UTC-8, liujisi wrote: >> >> The spec doesn't allow such conversion. If some language implementation >> supports the conversion, it is considered a bug by not following spec. >> >> Protobuf is designed to interop across different languages/platforms. >> Implicit conversion in "some libraries" allows creating non portable >> payload which leads to issues/surprises when you change the >> language/implementation in part of your pipeline, or communicate to a >> different party. >> >> That being said, you can propose to add the conversion to the spec to >> promote float->double promotion. That would require to change all the >> language implementations and we need to evaluate the cost and benefit. >> >> On Wednesday, November 15, 2017 at 10:18:15 PM UTC-8, James Philbin wrote: >>> >>> But the type stored on the wire is known - so it seems like it could be >>> supported (simply static_cast<double>(float_val)). By 'some libraries': >>> does the C++ ParseFromString method do this or not? >>> >>> Thanks! >>> James >>> >>> On Wed, Nov 15, 2017 at 3:57 PM Marc Gravell <marc.g...@gmail.com> >>> wrote: >>> >>>> Not really, no. They take different amounts of space on the wire, and >>>> have a different declared wire type (header). Some libraries may choose to >>>> be gracious and apply the conversion silently, but other libraries could >>>> just say "unexpected wire type" and stop processing. >>>> >>>> You could perhaps do it as a `oneof`, and have the client check both? >>>> >>>> On 15 Nov 2017 11:51 p.m., "James Philbin" <phil...@gmail.com> wrote: >>>> >>>>> Hi, >>>>> >>>>> Is it safe to upgrade float fields to doubles for serialized protos? >>>>> If not, why not? >>>>> >>>>> Thanks, >>>>> James >>>>> >>>>> -- >>>>> >>>> You received this message because you are subscribed to the Google >>>>> Groups "Protocol Buffers" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to protobuf+u...@googlegroups.com. >>>> >>>> >>>>> To post to this group, send email to prot...@googlegroups.com. >>>>> Visit this group at https://groups.google.com/group/protobuf. >>>>> For more options, visit https://groups.google.com/d/optout. >>>>> >>>> -- > You received this message because you are subscribed to the Google Groups > "Protocol Buffers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to protobuf+unsubscr...@googlegroups.com. > To post to this group, send email to protobuf@googlegroups.com. > Visit this group at https://groups.google.com/group/protobuf. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Protocol Buffers" group. To unsubscribe from this group and stop receiving emails from it, send an email to protobuf+unsubscr...@googlegroups.com. To post to this group, send email to protobuf@googlegroups.com. Visit this group at https://groups.google.com/group/protobuf. For more options, visit https://groups.google.com/d/optout.
