package ocaml-protoc
Protobuf compiler for OCaml
Install
Dune Dependency
Authors
Maintainers
Sources
2.4.0.tar.gz
md5=8a294e86c6202b8ec8016e71d19264cb
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doc/src/ocaml-protoc.compiler-lib/pb_codegen_decode_yojson.ml.html
Source file pb_codegen_decode_yojson.ml
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module Ot = Pb_codegen_ocaml_type module F = Pb_codegen_formatting let sp = Pb_codegen_util.sp let file_suffix = "yojson" (* Function which returns all the possible pattern match for reading a JSON value into an OCaml value. The protobuf JSON encoding rules are defined here: https://developers.google.com/protocol-buffers/docs/proto3#json *) let field_pattern_match ~r_name ~rf_label field_type = match field_type with | Ot.Ft_basic_type bt -> let runtime_f = match bt with | Ot.Bt_string -> "string" | Ot.Bt_float -> "float" | Ot.Bt_int -> "int" | Ot.Bt_int32 -> "int32" | Ot.Bt_int64 -> "int64" | Ot.Bt_uint32 -> "[`unsigned of int32]" | Ot.Bt_uint64 -> "[`unsigned of int64]" | Ot.Bt_bool -> "bool" | Ot.Bt_bytes -> "bytes" in ( "json_value", sp "Pbrt_yojson.%s json_value \"%s\" \"%s\"" runtime_f r_name rf_label ) | Ot.Ft_unit -> assert false (* TODO Wrapper: add similar one for wrapper type (with different runtime functions) *) | Ot.Ft_user_defined_type udt -> let f_name = let function_prefix = "decode" in let module_suffix = file_suffix in Pb_codegen_util.function_name_of_user_defined ~function_prefix ~module_suffix udt in let value_expression = "(" ^ f_name ^ " json_value)" in "json_value", value_expression | _ -> assert false (* Generate all the pattern matches for a record field *) let gen_rft_nolabel sc ~r_name ~rf_label (field_type, _, _) = let json_label = Pb_codegen_util.camel_case_of_label rf_label in let match_variable_name, exp = field_pattern_match ~r_name ~rf_label field_type in F.linep sc "| (\"%s\", %s) -> " json_label match_variable_name; F.linep sc " v.%s <- %s" rf_label exp (* Generate all the pattern matches for a repeated field *) let gen_rft_repeated_field sc ~r_name ~rf_label repeated_field = let _, field_type, _, _, _ = repeated_field in let json_label = Pb_codegen_util.camel_case_of_label rf_label in F.linep sc "| (\"%s\", `List l) -> begin" json_label; F.scope sc (fun sc -> F.linep sc "v.%s <- List.map (function" rf_label; let match_variable_name, exp = field_pattern_match ~r_name ~rf_label field_type in F.linep sc " | %s -> %s" match_variable_name exp; F.line sc ") l;"); F.line sc "end" let gen_rft_optional_field sc ~r_name ~rf_label optional_field = let field_type, _, _, _ = optional_field in let json_label = Pb_codegen_util.camel_case_of_label rf_label in let match_variable_name, exp = field_pattern_match ~r_name ~rf_label field_type in F.linep sc "| (\"%s\", %s) -> " json_label match_variable_name; F.linep sc " v.%s <- Some (%s)" rf_label exp (* Generate pattern match for a variant field *) let gen_rft_variant_field sc ~r_name ~rf_label { Ot.v_constructors; _ } = List.iter (fun { Ot.vc_constructor; vc_field_type; _ } -> let json_label = Pb_codegen_util.camel_case_of_constructor vc_constructor in match vc_field_type with | Ot.Vct_nullary -> F.linep sc "| (\"%s\", _) -> v.%s <- %s" json_label rf_label vc_constructor | Ot.Vct_non_nullary_constructor field_type -> let match_variable_name, exp = field_pattern_match ~r_name ~rf_label field_type in F.linep sc "| (\"%s\", %s) -> " json_label match_variable_name; F.linep sc " v.%s <- %s (%s)" rf_label vc_constructor exp) v_constructors (* Generate decode function for a record *) let gen_record ?and_ module_prefix { Ot.r_name; r_fields } sc = let mutable_record_name = Pb_codegen_util.mutable_record_name r_name in F.line sc @@ sp "%s decode_%s d =" (Pb_codegen_util.let_decl_of_and and_) r_name; F.scope sc (fun sc -> F.linep sc "let v = default_%s () in" mutable_record_name; F.line sc @@ "let assoc = match d with"; F.line sc @@ " | `Assoc assoc -> assoc"; F.line sc @@ " | _ -> assert(false)"; (* TODO raise E *) F.line sc @@ "in"; F.line sc "List.iter (function "; F.scope sc (fun sc -> (* Generate pattern match for all the possible message field *) List.iter (fun { Ot.rf_label; rf_field_type; _ } -> match rf_field_type with | Ot.Rft_nolabel nolabel_field -> gen_rft_nolabel sc ~r_name ~rf_label nolabel_field | Ot.Rft_repeated repeated_field -> gen_rft_repeated_field sc ~r_name ~rf_label repeated_field | Ot.Rft_variant variant_field -> gen_rft_variant_field sc ~r_name ~rf_label variant_field | Ot.Rft_optional optional_field -> gen_rft_optional_field sc ~r_name ~rf_label optional_field | Ot.Rft_required _ -> Printf.eprintf "Only proto3 syntax supported in JSON encoding"; exit 1 | Ot.Rft_associative _ -> Printf.eprintf "Map field are not currently supported for JSON"; exit 1) r_fields; (* Unknown fields are simply ignored *) F.empty_line sc; F.line sc "| (_, _) -> () (*Unknown fields are ignored*)"); F.line sc ") assoc;"; (* Transform the mutable record in an immutable one *) F.line sc "({"; F.scope sc (fun sc -> List.iter (fun { Ot.rf_label; _ } -> F.linep sc "%s_types.%s = v.%s;" module_prefix rf_label rf_label) r_fields); F.linep sc "} : %s_types.%s)" module_prefix r_name) (* Generate decode function for a variant type *) let gen_variant ?and_ module_prefix { Ot.v_name; v_constructors } sc = (* helper function for each constructor case *) let process_v_constructor sc { Ot.vc_constructor; vc_field_type; _ } = let json_label = Pb_codegen_util.camel_case_of_constructor vc_constructor in match vc_field_type with | Ot.Vct_nullary -> F.linep sc "| (\"%s\", _)::_-> (%s_types.%s : %s_types.%s)" json_label module_prefix vc_constructor module_prefix v_name | Ot.Vct_non_nullary_constructor field_type -> let match_, exp = let r_name = v_name and rf_label = vc_constructor in field_pattern_match ~r_name ~rf_label field_type in F.linep sc "| (\"%s\", %s)::_ -> " json_label match_; F.linep sc " (%s_types.%s (%s) : %s_types.%s)" module_prefix vc_constructor exp module_prefix v_name in F.linep sc "%s decode_%s json =" (Pb_codegen_util.let_decl_of_and and_) v_name; F.scope sc (fun sc -> (* even though a variant should be an object with a single field, * it is possible other fields are present in the JSON object. Therefore * we still need a loop to iterate over the key/value, even if in 99.99% * of the cases it will be a single iteration *) F.line sc "let assoc = match json with"; F.line sc " | `Assoc assoc -> assoc"; F.line sc " | _ -> assert(false)"; (* TODO raise E *) F.line sc "in"; F.line sc "let rec loop = function"; F.scope sc (fun sc -> (* termination condition *) F.linep sc "| [] -> Pbrt_yojson.E.malformed_variant \"%s\"" v_name; List.iter (process_v_constructor sc) v_constructors; F.empty_line sc; F.line sc "| _ :: tl -> loop tl"); F.line sc "in"; F.line sc "loop assoc") let gen_const_variant ?and_ module_prefix { Ot.cv_name; cv_constructors } sc = F.linep sc "%s decode_%s json =" (Pb_codegen_util.let_decl_of_and and_) cv_name; F.scope sc (fun sc -> F.line sc "match json with"; List.iter (fun { Ot.cvc_name; cvc_string_value; _ } -> F.linep sc "| `String \"%s\" -> (%s_types.%s : %s_types.%s)" cvc_string_value module_prefix cvc_name module_prefix cv_name) cv_constructors; F.linep sc "| _ -> Pbrt_yojson.E.malformed_variant \"%s\"" cv_name) let gen_struct ?and_ t sc = let { Ot.module_prefix; spec; _ } = t in let has_encoded = match spec with | Ot.Record r -> gen_record ?and_ module_prefix r sc; true | Ot.Variant v -> gen_variant ?and_ module_prefix v sc; true | Ot.Const_variant v -> gen_const_variant ?and_ module_prefix v sc; true in has_encoded let gen_sig ?and_ t sc = let _ = and_ in let { Ot.module_prefix; spec; _ } = t in let f type_name = F.linep sc "val decode_%s : Yojson.Basic.json -> %s_types.%s" type_name module_prefix type_name; F.linep sc ("(** [decode_%s decoder] decodes a " ^^ "[%s] value from [decoder] *)") type_name type_name in match spec with | Ot.Record { Ot.r_name; _ } -> f r_name; true | Ot.Variant { Ot.v_name; _ } -> f v_name; true | Ot.Const_variant { Ot.cv_name; _ } -> f cv_name; true let ocamldoc_title = "JSON Decoding"
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