fix: bare select() over a subquery or union selects every alias

.changeset/fromquery-select-all.md

@@ -0,0 +1,5 @@
+---
+"@maple-dev/effect-orm": patch
+---
+
+A bare `select()` over a subquery or union (`CH.fromQuery(inner, "w").select()`, `CH.fromUnion(union, "u").select()`) selects every alias the source selects, as its type already said. It died with `QueryBuilderDefect: select() is required`, because the derived source has no column list until its own SELECT is evaluated.

src/ch/compile.ts

@@ -759,7 +759,7 @@ function compileInner<
 		const $ = makeAccessor(state)
 
 		// SELECT
-		const selectExprs = state.selectFn ? state.selectFn($) : {}
+		const selectExprs = selectRecordOf(state, $) ?? {}
 		const keys = Object.keys(selectExprs)
 		if (
 			options?.selectKeys &&
@@ -1271,8 +1271,19 @@ export function selectedAliasesOf(query: CHQuery<any, any, any>): ReadonlyArray<
 
 /** Evaluate a query's SELECT callback without compiling it. */
 function selectExprsOf(query: CHQuery<any, any, any>): Record<string, unknown> | undefined {
-	const state = query._state
-	return state.selectFn ? state.selectFn(makeAccessor(state)) : undefined
+	return selectRecordOf(query._state, makeAccessor(query._state))
+}
+
+/**
+ * A query's SELECT list against accessor `$`: its callback's record, or for a
+ * bare `select()` over a subquery or union, every alias that source selects.
+ */
+function selectRecordOf(state: CHQueryState, $: any): Record<string, any> | undefined {
+	if (state.selectAll) {
+		const source = state.fromUnion ? unionExprsOf(state.fromUnion._state.queries) : state.fromQuery ? selectExprsOf(state.fromQuery) : undefined
+		return source === undefined ? undefined : Object.fromEntries(Object.keys(source).map((alias) => [alias, $[alias]]))
+	}
+	return state.selectFn?.($)
 }
 
 /**

src/ch/query.ts

@@ -126,6 +126,12 @@ export interface CHQueryState {
 	readonly tableAlias?: string
 	readonly columns: ColumnDefs
 	readonly selectFn?: ($: any) => SelectRecord
+	/**
+	 * A bare `select()` over a subquery or union: every alias the source
+	 * selects. Its columns are only known once the source's SELECT is evaluated,
+	 * which `compile` does, so the expansion waits for it.
+	 */
+	readonly selectAll?: true
 	readonly whereFn?: ($: any) => ReadonlyArray<Condition | undefined>
 	readonly groupByKeys: string[]
 	/** Post-aggregation filter. Deliberately NOT consulted when deriving tenant
@@ -569,11 +575,15 @@ function makeQuery<
 		_state: state,
 
 		select(...args: any[]): any {
-			if (args.length === 0) return makeQuery({ ...state, selectFn: selectEvery(Object.keys(state.columns)) })
+			if (args.length === 0) {
+				return state.fromQuery !== undefined || state.fromUnion !== undefined
+					? makeQuery({ ...state, selectFn: undefined, selectAll: true })
+					: makeQuery({ ...state, selectFn: selectEvery(Object.keys(state.columns)) })
+			}
 			// String overload: select("Col1", "Col2") → select($ => ({ Col1: $.Col1, Col2: $.Col2 }))
-			if (typeof args[0] === "string") return makeQuery({ ...state, selectFn: selectEvery(args as string[]) })
+			if (typeof args[0] === "string") return makeQuery({ ...state, selectFn: selectEvery(args as string[]), selectAll: undefined })
 			// Callback overload: select($ => ({ ... }))
-			return makeQuery({ ...state, selectFn: args[0] })
+			return makeQuery({ ...state, selectFn: args[0], selectAll: undefined })
 		},
 
 		where(fn) {

src/ch/subquery.test.ts

@@ -353,3 +353,21 @@ describe("CTE shadowing", () => {
 		expect(compiled.tenantScope).toBe("cross-tenant")
 	})
 })
+
+describe("bare select() over a derived source", () => {
+	const inner = CH.from(Events)
+		.select(($) => ({ trace: $.TraceId, total: CH.count(), raw: CH.untypedExpr("1") }))
+		.groupBy("trace")
+
+	it("selects every alias of a subquery, typed ones decoding as before", () => {
+		const compiled = compileCHUnsafe(CH.fromQuery(inner, "w").select(), {})
+		expect(compiled.sql).toContain("SELECT\n          w.trace AS trace,\n          w.total AS total,\n          w.raw AS raw")
+		expect(compiled.sql).toContain("FROM (")
+	})
+
+	it("selects every alias of a union", () => {
+		const branch = CH.from(Events).select(($) => ({ trace: $.TraceId }))
+		const { sql } = compileCHUnsafe(CH.fromUnion(CH.unionAll(branch, branch), "u").select(), {})
+		expect(sql).toContain("u.trace AS trace")
+	})
+})

tests/fuzz/known-issues.ts

@@ -123,13 +123,7 @@ const planIssues: ReadonlyArray<KnownIssue<PlanInput>> = [
 			target === "postgres" &&
 			[...nodes(plan)].some((node) => node.k === "value" && typeof node.v === "number" && !Number.isInteger(node.v)),
 	},
-	{
-		id: "fromquery-select-all",
-		reason:
-			"`CH.fromQuery(q, alias).select()` is typed as selecting every column, but a subquery source has no column " +
-			"list to expand, so compile dies with QueryBuilderDefect `select() is required`. `select(...names)` works.",
-		matches: ({ plan }) => plan.wrap === "all",
-	},
+
 ]
 
 export const knownPlanIssue = (input: PlanInput): string | undefined => firstMatch(planIssues, input)