fix(core): name an unnamed result column by position

targetName returned "?column?" for a result column with no alias that is
not a column reference or a function call. The Go generator uses a
non-empty name as written, so it emitted "var ?column? ..." and
sqlc generate failed with "illegal character U+003F".

Return an empty name. The generator already falls back to column_N for
an empty name, which is what the PostgreSQL and SQLite engines produce.

Adds the duckdb_unnamed_columns end-to-end case.

Author: xen0l

internal/core/analyzer/projection.go

@@ -105,6 +105,9 @@ func (a *analyzer) decorateSource(col *core.Column, attOID int64, tableAlias str
 
 // targetName picks the output name for a target. fields is the already
 // flattened field list when rt.Val is a column reference, and nil otherwise.
+// A target with no name returns "", so code generation names it by position
+// (column_1) as it does for the other engines. "?column?" is not a valid
+// identifier in the generated code.
 func targetName(rt *ast.ResTarget, fields []string) string {
 	if rt.Name != nil && *rt.Name != "" {
 		return *rt.Name
@@ -117,7 +120,7 @@ func targetName(rt *ast.ResTarget, fields []string) string {
 			return name
 		}
 	}
-	return "?column?"
+	return ""
 }
 
 func isStar(fields []string) bool {

internal/endtoend/testdata/duckdb_unnamed_columns/duckdb/exec.json

@@ -0,0 +1 @@
+{"contexts": ["base"]}

internal/endtoend/testdata/duckdb_unnamed_columns/duckdb/go/db.go

@@ -0,0 +1,11 @@
+-- name: Cast :many
+SELECT CAST(age AS BIGINT) FROM people;
+
+-- name: Concat :many
+SELECT name || '!' FROM people;
+
+-- name: Two :many
+SELECT id + 1, age * 2 FROM people;
+
+-- name: Mixed :many
+SELECT id, upper(name), age + 1 AS next_age, id * 2 FROM people;

internal/endtoend/testdata/duckdb_unnamed_columns/duckdb/go/models.go

@@ -0,0 +1 @@
+CREATE TABLE people (id INTEGER NOT NULL, name VARCHAR NOT NULL, age INTEGER);

internal/endtoend/testdata/duckdb_unnamed_columns/duckdb/go/query.sql.go

@@ -0,0 +1,10 @@
+version: "2"
+sql:
+  - engine: "duckdb"
+    schema: "schema.sql"
+    queries: "query.sql"
+    gen:
+      go:
+        package: "querytest"
+        out: "go"
+        sql_package: "database/sql"