fix(codegen): Never generate return structs for :exec (#2976)

* fix(codegen): Never generate return structs for :exec

* fix(validate): Ensure batch commands have return values

* Fix test output

Author: kyleconroy

internal/codegen/golang/result.go

@@ -312,16 +312,16 @@ func buildQueries(req *plugin.GenerateRequest, options *opts.Options, structs []
 	return qs, nil
 }
 
+var cmdReturnsData = map[string]struct{}{
+	metadata.CmdBatchMany: {},
+	metadata.CmdBatchOne:  {},
+	metadata.CmdMany:      {},
+	metadata.CmdOne:       {},
+}
+
 func putOutColumns(query *plugin.Query) bool {
-	if len(query.Columns) > 0 {
-		return true
-	}
-	for _, allowed := range []string{metadata.CmdMany, metadata.CmdOne, metadata.CmdBatchMany} {
-		if query.Cmd == allowed {
-			return true
-		}
-	}
-	return false
+	_, found := cmdReturnsData[query.Cmd]
+	return found
 }
 
 // It's possible that this method will generate duplicate JSON tag values

internal/codegen/golang/result_test.go

@@ -50,7 +50,7 @@ func TestPutOutColumns_ForZeroColumns(t *testing.T) {
 		},
 		{
 			cmd:  metadata.CmdBatchOne,
-			want: false,
+			want: true,
 		},
 	}
 	for _, tc := range tests {

internal/endtoend/testdata/cte_left_join/postgresql/pgx/go/query.sql.go

@@ -0,0 +1 @@
+https://github.com/sqlc-dev/sqlc/issues/2970

internal/endtoend/testdata/exec_no_return_struct/issue.md

@@ -0,0 +1,13 @@
+-- name: ResetTaskRun :exec
+UPDATE job
+SET last_run = NOW()
+FROM (
+        SELECT last_run,
+            task_name
+        FROM job AS o
+        WHERE o.task_name = $1 
+  		FOR UPDATE
+    ) AS old_values
+WHERE job.task_name = $1
+RETURNING job.last_run AS this_run,
+    old_values.last_run AS last_run;

internal/endtoend/testdata/exec_no_return_struct/postgresql/pgx/go/db.go

@@ -0,0 +1,5 @@
+CREATE TABLE IF NOT EXISTS job
+(
+    task_name text NOT NULL,
+    last_run timestamp with time zone DEFAULT now() NOT NULL
+);

internal/endtoend/testdata/exec_no_return_struct/postgresql/pgx/go/models.go

@@ -0,0 +1,10 @@
+version: "2"
+sql:
+  - engine: "postgresql"
+    schema: "schema.sql"
+    queries: "query.sql"
+    gen:
+      go:
+        package: "querytest"
+        out: "go"
+        sql_package: "pgx/v5"