Module gpb_compile

opt() = type_specs | {type_specs, boolean() | preferably} | {verify, optionally | always | never} | {copy_bytes, true | false | auto | integer() | float()} | {strings_as_binaries, boolean()} | strings_as_binaries | boolean_opt(defs_as_proplists) | boolean_opt(descriptor) | boolean_opt(maps) | boolean_opt(msgs_as_maps) | boolean_opt(mapfields_as_maps) | boolean_opt(defs_as_maps) | {maps_unset_optional, omitted | present_undefined} | boolean_opt(nif) | {load_nif, string()} | {i, directory()} | {o, directory()} | {o_erl, directory()} | {o_hrl, directory()} | {o_nif_cc, directory()} | binary | to_proto_defs | to_msg_defs | return | boolean_opt(return_warnings) | boolean_opt(return_errors) | report | boolean_opt(report_warnings) | boolean_opt(report_errors) | boolean_opt(warnings_as_errors) | boolean_opt(include_as_lib) | boolean_opt(use_packages) | {erlc_compile_options, string()} | {rename, renaming()} | {msg_name_prefix, string() | atom() | {by_proto, prefix_by_proto()}} | {msg_name_suffix, string() | atom()} | boolean_opt(msg_name_to_snake_case) | boolean_opt(msg_name_to_lower) | {module_name_prefix, string() | atom()} | {module_name_suffix, string() | atom()} | {module_name, string() | atom()} | {any_translate, [translation()]} | boolean_opt(epb_compatibility) | boolean_opt(epb_functions) | boolean_opt(defaults_for_omitted_optionals) | boolean_opt(type_defaults_for_omitted_optionals) | {import_fetcher, import_fetcher_fun()} | {target_erlang_version, integer() | current} | term()

opts()

opts() = [opt()]

prefix_by_proto()

prefix_by_proto() = [{ProtoName::atom(), Prefix::string() | atom()}]

reason()

reason() = term()

renaming()

renaming() = {pkg_name, name_change()} | {msg_name, msg_name_change()} | {msg_fqname, msg_name_change()} | {group_name, name_change()} | {group_fqname, name_change()} | {service_name, name_change()} | {service_fqname, name_change()} | {rpc_name, name_change()}

translation()

translation() = {encode, mod_fn_argtemplate()} | {decode, mod_fn_argtemplate()} | {merge, mod_fn_argtemplate()} | {verify, mod_fn_argtemplate()}

warning()

warning() = term()

Function Index

c/0	Command line interface for the compiler.
c/1	This function is intended as a command line interface for the compiler.
c/2
file/1	Equivalent to `file(File, [])`.
file/2	Compile a .proto file to a .erl file and to a .hrl file.
format_error/1	Produce a plain-text error message from a reason returned by for instance `file/2` or `proto_defs/2`.
format_warning/1	Produce a plain-text error message from a reason returned by for instance `file/2` or `proto_defs/2`.
locate_import/2	Locate an import target.
msg_defs/2	Deprecated, use proto_defs/2 instead.
msg_defs/3	Deprecated, use proto_defs/2 instead.
parse_opts_and_args/1
proto_defs/2	Equivalent to `proto_defs(Mod, Defs, [])`.
proto_defs/3	Compile a list of pre-parsed definitions to file or to a binary.
read_import/2	Read an import file.
show_args/0
show_version/0
string/2	Equivalent to `string(Mod, Str, [])`.
string/3	Compile a `.proto` file as string.

Function Details

c/0

c() -> no_return()

Command line interface for the compiler. With no proto file to compile, print a help message and exit.

c/1

c(Files::[string() | atom()]) -> no_return()

This function is intended as a command line interface for the compiler. Call it from the command line as follows:

     erl <erlargs> [gpb-opts] -s gpb_compile c File.proto ...
     erl <erlargs> -s gpb_compile c File.proto ... -extra [gpb-opts]

The <erlargs> can be -noshell -noinput +B -boot start_clean -pa SomeDir

The options below are supported. Dashes and underscores inside option names are equivalent, ie -o-erl and -o_erl are the same option.

-IDir -I Dir

Specify include directory. Option may be specified more than once to specify several include directories.

-o Dir

Specify output directory for where to generate the ProtoFile.erl and ProtoFile.hrl

-o-erl Dir | -o-hrl Dir | -o-nif-cc Dir

Specify output directory for where to generate the ProtoFile.erl and ProtoFile.hrl respectively, and for the NIF C++ file, if the -nif option is specified. The -o-erl Dir option overrides any -o Dir option, and similarly for the other file-type specific output options.

-v optionally | always | never

Specify how the generated encoder should verify the message to be encoded.

-nif

Generate nifs for linking with the protobuf C(++) library.

-load_nif FunctionDefinition

Specify FunctionDefinition as the text that defines the function load_nif/0. This is called as the on_load hook for loading the NIF. See also the doc for the load_nif option in the file/2 function.

-c true | false | auto | integer() | float()

Specify how or when the generated decoder should copy fields of type bytes. See the copy_bytes option for the function file/2 for more info.

-strbin

Specify that decoded strings should be returned as binaries, instead of as strings (lists).

-pldefs

Specify that introspection functions shall return proplists instead of #field{} records, to make the generated code completely free of even compile-time dependencies to gpb.

-pkgs

Prepend the name of a package to every message it contains. If no package is defined, nothing will be prepended. Default is to not prepend package names for backwards compatibility, but it is needed for some proto files.

-any_translate MsFs

Call functions in MsFs to pack, unpack, merge and verify google.protobuf.Any messages. The MsFs is a string on the following format: e=Mod:Fn,d=Mod:Fn[,m=Mod:Fn][,V=Mod:Fn]. The specified modules and functinos are called and used as follows:

e=Mod:Fn: Call Mod:Fn(Term) to pack the Term to a google.protobuf.Any message.
d=Mod:Fn: Call Mod:Fn(Any) to unpack the Any to unpack a google.protobuf.Any message to a term.
m=Mod:Fn: Call Mod:Fn(Term1, Term2) -> Term3 to merge two unpacked terms to a resulting Term3.
V=Mod:Fn: Call Mod:Fn(Term) -> _ to verify an unpacked Term. If Term is valid, the function is expected to just return any value, which is ignored and discarded. If Term is invalid, the function is exptected to not return anything, but instead either crash, call erlang:error/1, or throw/1 or exit/1. with the reason for error. If you want to use a verifier, this is the new preferred approach.
v=Mod:Fn: Call Mod:Fn(Term, ErrorF) -> _ to verify an unpacked Term. This exists for backwards compatibility, and its use is deprecated.

-msgprefix Prefix

Prefix each message with Prefix. This can be useful to when including different sub-projects that have colliding message names.

-modprefix Prefix

Prefix each module with Prefix. Normally the module name of the generated code is based on the name of the .proto file. This option prepends a prefix to the module name, which can be useful when including different sub-projects that have colliding proto file names.

-msgsuffix Suffix

Suffix each message name with Suffix.

-modsuffix Suffix

Suffix each module name with Suffix.

-modname Name

Specify the name of the generated module.

-msgtolower

ToLower each message. Any prefixes/suffixes are added after case modification.

-il

Generate code that include gpb.hrl using -include_lib instead of -include, which is the default.

-type -no_type

Enables or disables ::Type() annotations in the generated code. Default is to enable if there are no cyclic dependencies.

-descr

Generate self-description information.

-maps

This option expands to the following options:

-msgs-as-maps
-mapfields-as-maps
-defs-as-maps

See the maps option for the function file/2 for more info.

-maps_unset_optional omitted | present_undefined

Specifies the internal format for optional fields that are unset.

-msgs-as-maps

Specifies that messages should be maps. No .hrl file will be generated. Without this option, messages will be records.

-mapfields-as-maps

Specifies that fields of type map<_,_> should be maps. Otherwise, they will be 2-tuples.

-defs-as-maps

Specifies that proto defintions from the generated code are to be returned as maps. Otherwise, they will be lists of tuples and records (or proplists if the -pldefs option is specified)

-erlc_compile_options Options

Specifies compilation options, in a comma separated string, to pass along to the -compile(...) directive on the generated code.

-epb

Enable compatibility with the Erlang Protobuffs library:

Implies the -epb-functions option
Implies the -defaults-for-omitted-optionals option
Implies the -modsuffix _pb option
Implies the -msgtolower option

-epb-functions

For compatibility with the Erlang Protobuffs library, generate also the following functions: encode/1, decode/2, encode_MsgName/1 and decode_MsgName/1

-defaults-for-omitted-optionals

For optional fields not present on decoding, set the field to its default value, if any, instead of to undefined.

-type-defaults-for-omitted-optionals

For optional fields not present on decoding, set the field to its type-default, instead of to undefined.

-for-version N

Generate code for Erlang/OTP version N instead of current.

-Werror, -W1, -W0, -W, -Wall

-Werror means treat warnings as errors
-W1 enables warnings, -W0 disables warnings.
-W and -Wall are the same as -W1

--help or -h

Show help.

--version or -V

Show the version number of gpb.

If several files are specified, each is compiled individually, no checking is done for instance for multiply defined messages or fields across files, such as the protoc does.

c/2

c(Opts::opts(), Args::[ProtoFileName::string()]) -> no_return()

file/1

file(File::string()) -> comp_ret()

Equivalent to file(File, []).

file/2

file(File::string(), Opts::opts()) -> comp_ret()

Compile a .proto file to a .erl file and to a .hrl file.

The File argument must not include path to the .proto file. Example: "SomeDefinitions.proto" is ok, while "/path/to/SomeDefinitions.proto" is not ok.

The .proto file is expected to be found in a directories specified by an {i,directory()} option. It is possible to specify {i,directory()} several times, they will be searched in the order specified.

The type_specs option enables or disables ::Type() annotations in the generated .hrl file. Default is true if there are no cyclic message dependencies. The default changed in gpb version 4.0.0. Previously, the default was false. If you have messages referencing other messages cyclically, and get into troubles when compiling the generated files, set this to false.

The verify option specifies whether or not to generate code that verifies, during encoding, that values are of correct type and within range. The verify option can have the following values:

always: Generate code that unconditionally verifies values.
never: Generate code that never verifies values time. Encoding will fail if a value of the wrong type is supplied. This includes forgetting to set a required message field. Encoding may silently truncate values out of range for some types.
optionally: Generate an encode_msg/2 that accepts the run-time option verify or {verify,boolean()} for specifying whether or not to verify values.

Erlang value verification either succeeds or crashes with the error {gpb_type_error,Reason}. Regardless of the verify option, a function, verify_msg/1 is always generated.

The copy_bytes option specifies whether when decoding data of type bytes (or strings if the strings_as_binaries is set), the decoded bytes should be copied or not. Copying requires the binary module, which first appeared in Erlang R14A. When not copying decoded bytes, they will become sub binaries of the larger input message binary. This may tie up the memory in the input message binary longer than necessary after it has been decoded. Copying the decoded bytes will avoid creating sub binaries, which will in turn make it possible to free the input message binary earlier. The copy_bytes option can have the following values:

false: Never copy bytes/(sub-)binaries.
true: Always copy bytes/(sub-)binaries.
auto: Copy bytes/(sub-)binaries if the beam vm, on which the compiler (this module) is running, has the binary:copy/1 function. (This is the default)
integer() | float(): Copy the bytes/(sub-)binaries if the message this many times or more larger than the size of the bytes/(sub-)binary.

The strings_as_binaries option specifies whether strings should be returned from decoding as strings (list of Unicode code points), or as binaries (UTF-8 encoded). The copy_bytes option applies to strings as well, when the strings_as_binaries option is set. Upon encoding, both binaries and iolists are accepted.

The defs_as_proplists option changes the generated introspection functions find_msg_def and get_msg_defs to return the description of each message field as a proplist, instead of as a #field{} record. The purpose is to make the generated code completely independent of gpb, at compile-time (it is already independent at run-time). The keys of the proplist are the names of the record fields in the #field{} record. See also gpb:proplists_to_field_records() and related functions for conversion functions between these two formats.

The descriptor option specifies whether or not to generate a function, descriptor/0, which returns a binary that describes the proto file(s) contents according to the protobuf's descriptor.proto. The default is to not generate such a description. The generated description binary is most likely not identical to what protoc would generate, but the contents is roughly equivalent.

The {o,directory()} option specifies directory to use for storing the generated .erl and .hrl files. Default is the same directory as for the proto File.

The {o_erl,directory()}, {o_hrl,directory()}, {o_nif_cc,directory()}, options specify output directories for where to generate the .erl and .hrl files respectively, and for the NIF C++ file, if the nif option is specified. The {o_erl,directory()} option overrides any {o,directory()} option, and similarly for the other file-type specific output options.

The maps option will generate a protobuf encoder/decoder that uses maps instead of records. This option expands to the following options:

msgs_as_maps: No .hrl file will be generated, and the functions encode_msg, merge_msgs and verify_msg will take the message name as an additional parameter.
mapfields_as_maps: The value for fields of type map<_,_> will be a map instead of a list of 2-tuples.
defs_as_maps: The introspection will generate message field descriptions as maps instead of as #field{} records, unless, of course defs_as_proplists is specified, in which case they will be proplists instead.

For messages as maps, for optional fields, if not set, the maps_unset_optional option specifies the Erlang-internal representation; both how it is expected to be found at encoding, and how decoding will return it:

omitted: This means it is not included in the map. This is the default. (since gpb version 4.0.0)
present_undefined: This means it is present and has the value undefined. This was the default before gpb version 4.0.0.

The nif option will cause the compiler to generate nif C++ code for encoding and decoding. The generated nif C++ code can be linked with the Google protobuf C++ library. Read the file README.nif-cc for more info. This option is not compatible with the maps option; the generated C++ decoding code would still create records.

The binary option will cause the generated and compiled code to be returned as a binary. No files will be written. The return value will be on the form {ok,Mod,Code} or {ok,Mod,Code,Warnings} if the compilation is successful. This option may be useful e.g. when generating test cases. In case the nif option is set, the Code will be a list of tuples: {erl,binary()} which contains the Erlang object byte code, and {nif,binary()} which contains the C++ code. You will have to compile the C++ code with a C++ compiler, before you can use the Erlang code.

The to_proto_defs option will result in {ok,Defs} or {ok,Defs,Warns} being returned if the compilation is successful. The returned message definitions can be used with the proto_defs/2 or proto_defs/3 functions.

The to_msg_defs option is a deprecated alias for to_proto_defs.

report_errors/report_warnings: Causes errors/warnings to be printed as they occur.
report: This is a short form for both report_errors and report_warnings.
return_errors: If this flag is set, then {error,ErrorList,WarningList} is returned when there are errors.
return_warnings: If this flag is set, then an extra field containing WarningList is added to the tuples returned on success.
return: This is a short form for both return_errors and return_warnings.

Setting the warnings_as_errors option will cause warnings to be treated as errors. If there are warnings but no errors, and return_warnings is not specified, then error will be returned.

See format_error/1 for a way to turn an error Reason to plain text.

If the include_as_lib option is set, the generated code will include gpb.hrl as a library, which is necessary if dependencies are managed with Rebar. Otherwise, the header file is included directly and must be located in the path, which is default behavior.

The use_packages option instructs gpb to prepend the name of a package to every message it contains. If no package is defined, nothing will be prepended. This enables the reference of messages in other packages which would otherwise not be possible. However, for reasons of backward compatibility, this option is disabled by default.

If the the {erlc_compile_options,string()} option is set, then the genereted code will contain a directive -compile([String]).

The {rename,{What,How}} can transform message names, package names, service and rpc names in various ways. This option supersedes the options {msg_name_prefix,Prefix}, {msg_name_suffix,Suffix}, msg_name_to_lower and msg_name_to_snake_case, while at the same time giving more fine-grained control. It is for example possible to apply snake_casing only to the message name, while keeping the package name, the service name and the rpc name intact. This can be useful with grpc, where these name components are exposed. The msg_fqname refers to the fully qualified message name, as in Package.MsgName, while the msg_name refers to just the message name without package. The service_fqname and service_name specifiers work analogously.

It is possible to stack rename options, and they will be applied in the order they are specified. So it is for example possible to snake_case a name, and then also prefix it.

The {msg_name_prefix,Prefix} will add Prefix (a string or an atom) to each message. This might be useful for resolving colliding names, when incorporating several protocol buffer definitions into the same project. The {msg_name_suffix,Suffix} works correspondingly.

The {msg_name_prefix,Prefix} option expands to [{rename,{pkg_name,Prefix}},{rename,{msg_fqname,{prefix,Prefix}}}, {rename,{group_fqname,{prefix,Prefix}}}}], and ditto for suffixes.

For backwards compatibility, the {msg_name_prefix,{by_proto,PrefixList}} expands to just [{rename,{msg_fqname,{prefix,PrefixList}}}].

The msg_name_to_lower and msg_name_to_snake_case options expands to [{rename,{pkg_name,X}},{rename,{service_fqname,X}}, {rename,{rpc_name,X}},{rename,{msg_fqname,X}}, {rename,{rpc_name,X}},{rename,{group_fqname,X}}] where X is lowercase or snake_case respectively.

The {module_name_prefix,Prefix} will add Prefix (a string or an atom) to the generated code and definition files. The {module_name_suffix,Suffix} works correspondingly. For the case of compatibility with Erlang Protobuffs, the epb_compatibility option implies {module_name_suffix,"_pb"}

The {module_name,Name} can be used to specify the module name of the generated code freely, instead of basing it on the proto file name. The name specified with module_name can be prefixed and suffixed with the module_name_prefix and module_name_suffix options.

format_error/1

format_error(Reason::{error, Reason} | Reason) -> io_list()

Reason = term()

Produce a plain-text error message from a reason returned by for instance file/2 or proto_defs/2.

format_warning/1

format_warning(X::warning()) -> iolist()

Produce a plain-text error message from a reason returned by for instance file/2 or proto_defs/2.

locate_import/2

locate_import(ProtoFileName::string(), Opts::opts()) -> {ok, File::string()} | {error, reason()}

Locate an import target. This function might be potentially useful for instance in an intercepting import_fetcher fun that just wants to record the accessed imports.

msg_defs/2

msg_defs(Mod::module(), Defs::gpb_parse:defs()) -> comp_ret()

Equivalent to msg_defs(Mod, Defs, []).

Deprecated, use proto_defs/2 instead.

msg_defs/3

msg_defs(Mod, Defs, Opts) -> CompRet

Equivalent to proto_defs(Mod, Defs, Opts).

Deprecated, use proto_defs/2 instead.

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