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Generate Go interfaces for discriminators #68

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117 changes: 92 additions & 25 deletions crates/target_go/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -259,27 +259,12 @@ impl jtd_codegen::target::Target for Target {
writeln!(out)?;
write!(out, "{}", description(&metadata, 0))?;
writeln!(out, "type {} struct {{", name)?;
writeln!(out, "\t{} string", tag_field_name)?;
for variant in &variants {
writeln!(out)?;
writeln!(out, "\t{} {}", &variant.field_name, &variant.type_name)?;
}
writeln!(out, "\tValue I{} `json:\"-\"`", name)?;
writeln!(out, "}}")?;

writeln!(out)?;
writeln!(out, "func (v {}) MarshalJSON() ([]byte, error) {{", name)?;
writeln!(out, "\tswitch v.{} {{", tag_field_name)?;
for variant in &variants {
writeln!(out, "\tcase {:?}:", variant.tag_value)?;
writeln!(out, "\t\treturn json.Marshal(struct {{ T string `json:\"{}\"`; {} }}{{ v.{}, v.{} }})", tag_json_name, variant.type_name, tag_field_name, variant.field_name)?;
}
writeln!(out, "\t}}")?;
writeln!(out)?;
writeln!(
out,
"\treturn nil, fmt.Errorf(\"bad {0} value: %s\", v.{0})",
tag_field_name
)?;
writeln!(out, "\treturn json.Marshal(v.Value)")?;
writeln!(out, "}}")?;

writeln!(out)?;
Expand All @@ -293,32 +278,114 @@ impl jtd_codegen::target::Target for Target {
writeln!(out, "\t\treturn err")?;
writeln!(out, "\t}}")?;
writeln!(out)?;
writeln!(out, "\tvar value I{}", name)?;
writeln!(out, "\tvar err error")?;
writeln!(out)?;
writeln!(out, "\tswitch t.T {{")?;
for variant in &variants {
writeln!(out, "\tcase {:?}:", variant.tag_value)?;
writeln!(
out,
"\t\terr = json.Unmarshal(b, &v.{})",
variant.field_name
)?;
writeln!(out, "\t\tvar v {}", variant.type_name)?;
writeln!(out, "\t\terr = json.Unmarshal(b, &v)")?;
writeln!(out, "\t\tvalue = v")?;
}
writeln!(out, "\tdefault:")?;
writeln!(
out,
"\t\terr = fmt.Errorf(\"bad {} value: %s\", t.T)",
tag_field_name
"\t\terr = fmt.Errorf(\"{}: bad {} value: %q\", t.T)",
name, tag_json_name
)?;
writeln!(out, "\t}}")?;
writeln!(out)?;
writeln!(out, "\tif err != nil {{")?;
writeln!(out, "\t\treturn err")?;
writeln!(out, "\t}}")?;
writeln!(out)?;
writeln!(out, "\tv.{} = t.T", tag_field_name)?;
writeln!(out, "\tv.Value = value")?;
writeln!(out, "\treturn nil")?;
writeln!(out, "}}")?;

writeln!(out)?;
writeln!(
out,
"// I{} is an interface type that {} types implement.",
name, name
)?;
writeln!(out, "// It can be the following types:")?;
writeln!(out, "//")?;
for variant in &variants {
writeln!(
out,
"// - [{}] ({})",
&variant.type_name, &variant.tag_value
)?;
}
writeln!(out, "//")?;
writeln!(out, "type I{} interface {{", name)?;
writeln!(out, "\t{}() string", tag_field_name)?;
writeln!(out, "\tis{}()", name)?;
writeln!(out, "}}")?;
writeln!(out)?;

for variant in &variants {
writeln!(
out,
"func ({}) {}() string {{ return {:?} }}",
variant.type_name, tag_field_name, variant.tag_value
)?;
}
writeln!(out)?;

for variant in &variants {
writeln!(out, "func ({}) is{}() {{}}", variant.type_name, name)?;
}
writeln!(out)?;

for variant in &variants {
writeln!(
out,
"func (v {}) MarshalJSON() ([]byte, error) {{",
variant.type_name
)?;
writeln!(out, "\ttype Alias {}", variant.type_name)?;
writeln!(out, "\treturn json.Marshal(struct {{")?;
writeln!(out, "\t\tT string `json:\"{}\"`", tag_json_name)?;
writeln!(out, "\t\tAlias")?;
writeln!(out, "\t}}{{")?;
writeln!(out, "\t\tv.{}(),", tag_field_name)?;
writeln!(out, "\t\tAlias(v),")?;
writeln!(out, "\t}})")?;
writeln!(out, "}}")?;
writeln!(out)?;

writeln!(
out,
"func (v *{}) UnmarshalJSON(b []byte) error {{",
variant.type_name
)?;
writeln!(out, "\ttype Alias {}", variant.type_name)?;
writeln!(out, "\tvar a struct {{")?;
writeln!(out, "\t\tT string `json:\"{}\"`", tag_json_name)?;
writeln!(out, "\t\tAlias")?;
writeln!(out, "\t}}")?;
writeln!(out)?;
writeln!(out, "\tif err := json.Unmarshal(b, &a); err != nil {{")?;
writeln!(out, "\t\treturn err")?;
writeln!(out, "\t}}")?;
writeln!(out)?;
writeln!(out, "\tif a.T != {:?} {{", variant.tag_value)?;
writeln!(
out,
"\t\treturn fmt.Errorf(\"{}: bad {} value: %q\", a.T)",
variant.type_name, tag_json_name
)?;
writeln!(out, "\t}}")?;
writeln!(out)?;
writeln!(out, "\t*v = {}(a.Alias)", variant.type_name)?;
writeln!(out, "\treturn nil")?;
writeln!(out, "}}")?;
writeln!(out)?;
}

None
}

Expand Down