Expand discriminated unions in action templates

[Dominic Nguyen (datduyng)]

Before (broken)

toTemplateType always collapsed every type-union to the first arm:

functiontoTemplateType(type: ActionParamType,visited: ReadonlySet<string>=newSet<string>(),): TemplateType|undefined{switch(type.type){case"type-union":
// TODO: smarter about type unions.returntoTemplateType(type.types[0],visited);// ← always arm 0// ...}}// parameters built with no current values:consttype=toTemplateType(actionParametersType);

For player MusicTarget, that means the form template only ever sees the track arm:

// playerSchema.ts — 7 authored armsexporttypeMusicTarget=|PlayByTrack// kind: "track"|PlayByArtist// kind: "artist"|PlayByAlbum// kind: "album"|PlayByGenre// kind: "genre"|PlayByPlaylist// kind: "playlist"|PlayByDescription// kind: "description"|PlayAnyMusic;// kind: "any"exportinterfacePlayByTrack{kind: "track";trackName: string;artists?: string[];albumName?: string;}exportinterfacePlayByArtist{kind: "artist";artist: string;genre?: string;}exportinterfacePlayByAlbum{kind: "album";albumName: string;artists?: string[];}// ... genre / playlist / description / any

// template produced BEFORE (union → types[0] only){type: "object",fields: {kind: {type: {type: "string-union",typeEnum: ["track"]}},// ← only tracktrackName: {type: {type: "string"}},artists: {optional: true,type: {type: "array",elementType: {type: "string"}}},albumName: {optional: true,type: {type: "string"}},}}// lost: artist | album | genre | playlist | description | any

kind enum visible in template: [ 'track' ]
template only exposes first kind: [ 'track' ]
lost arms: [ 'artist', 'album', 'genre', 'playlist', 'description', 'any' ]
RESULT: BUG REPRODUCED

---

After (fixed)

Pass current parameter data into template conversion, detect MusicTarget-style discriminated object unions, emit the fullkind enum, and select arm fields from data.kind:

// Wire current values so the selected arm can be resolvedconsttype=toTemplateType(actionParametersType,newSet(),action.parameters,// ← was missing);

functiontoTemplateType(type: ActionParamType,visited: ReadonlySet<string>=newSet<string>(),data: unknown=undefined,): TemplateType|undefined{switch(type.type){case"type-union":
returntoTemplateTypeUnion(type.types,visited,data);case"type-reference":
// ... resolve, pass data through ...returntoTemplateType(type.definition.type,nextVisited,data);case"object":
returntoTemplateTypeObject(type,visited,data);case"array":
returntoTemplateTypeArray(type,visited,data);// ...}}

functiontoTemplateTypeUnion(types: readonlyActionParamType[],visited: ReadonlySet<string>,data: unknown,): TemplateType|undefined{constdisc=getObjectUnionDiscriminator(types);if(disc!==undefined){const{ fieldName, values, arms }=disc;letselectedIndex=0;if(data!==null&&typeofdata==="object"&&!Array.isArray(data)&&fieldNamein(dataasobject)){constcurrent=(dataasRecord<string,unknown>)[fieldName];if(typeofcurrent==="string"){constidx=values.indexOf(current);if(idx>=0)selectedIndex=idx;}}consttemplate=toTemplateTypeObject(arms[selectedIndex],visited,data);// Full enum so the UI can switch arms; discriminator triggers schema refresh.template.fields[fieldName]={optional: false,type: {type: "string-union",typeEnum: values,// all 7 kindsdiscriminator: values[selectedIndex],},};returntemplate;}// Non-discriminated: first-arm fallback (historical behavior)returntoTemplateType(types[0],visited,data);}

// Discriminator discovery: every arm is an object with the same single-value// string-union field (e.g. kind: "track" | kind: "artist" | …)functiongetObjectUnionDiscriminator(types: readonlyActionParamType[],): {fieldName: string;values: string[];arms: ActionParamObject[]}|undefined{if(types.length<2)returnundefined;constarms: ActionParamObject[]=[];for(consttoftypes){constobj=resolveObjectType(t);if(obj===undefined)returnundefined;arms.push(obj);}for(constfieldNameofObject.keys(arms[0].fields)){constvalues: string[]=[];letok=true;for(constarmofarms){constfield=arm.fields[fieldName];if(field===undefined||field.optional){ok=false;break;}constft=resolveTypeReference(field.type)??field.type;if(ft.type!=="string-union"||ft.typeEnum.length!==1){ok=false;break;}values.push(ft.typeEnum[0]);}if(!ok)continue;if(newSet(values).size!==values.length)continue;// must uniquely selectreturn{ fieldName, values, arms };}returnundefined;}

// template produced AFTER — data.kind = "album"{type: "object",fields: {kind: {type: {type: "string-union",typeEnum: ["track","artist","album","genre","playlist","description","any",],discriminator: "album",},},albumName: {type: {type: "string"}},artists: {optional: true,type: {type: "array",elementType: {type: "string"}}},}}

// AFTER — data.kind = "track"
fields: ["kind","trackName","artists","albumName"]
kind enum: [track,artist,album,genre,playlist,description,any]
discriminator: "track"// AFTER — data.kind = "artist"
fields: ["kind","artist","genre"]
discriminator: "artist"// AFTER — data.kind = "album"
fields: ["kind","albumName","artists"]
discriminator: "album"

RESULT: FIX VERIFIED
full kind enum on template: [track, artist, album, genre, playlist, description, any]