address PR feedback

cmd/super/compile/command.go

@@ -13,7 +13,7 @@ var spec = &charm.Spec{
 	Short: "compile a local query for inspection and debugging",
 	Long: `
 This command parses a query and emits the resulting abstract syntax
-tree (AST) or runtime directed-acycle graph (DAG) in the output format desired.
+tree (AST) or runtime directed acyclic graph (DAG) in the output format desired.
 Use "-dag" to specify the DAG form; otherwise, the AST form is assumed.
 
 The query text may be either SQL or SPQ.  To force parsing as SQL,

cmd/super/compile/shared.go

@@ -17,6 +17,7 @@ import (
 	"github.com/brimdata/super/lake"
 	"github.com/brimdata/super/pkg/storage"
 	"github.com/brimdata/super/runtime"
+	"github.com/brimdata/super/zbuf"
 	"github.com/brimdata/super/zfmt"
 	"github.com/brimdata/super/zio"
 	"github.com/brimdata/super/zson"
@@ -117,19 +118,9 @@ func (s *Shared) writeValue(ctx context.Context, v any) error {
 	if err != nil {
 		return err
 	}
-	err = zio.CopyWithContext(ctx, writer, &valReader{&val})
+	err = zio.CopyWithContext(ctx, writer, zbuf.NewArray([]super.Value{val}))
 	if closeErr := writer.Close(); err == nil {
 		err = closeErr
 	}
 	return err
 }
-
-type valReader struct {
-	*super.Value
-}
-
-func (r *valReader) Read() (*super.Value, error) {
-	val := r.Value
-	r.Value = nil
-	return val, nil
-}

compiler/ztests/from-error.yaml

@@ -1,4 +1,5 @@
 script: |
+  ! super compile -C -dag 'from p'
   export SUPER_DB_LAKE=test
   super db init -q
   ! super db compile -C -dag 'from test'
@@ -13,6 +14,9 @@ script: |
 outputs:
   - name: stderr
     data: |
+      "from pool" cannot be used without a lake at line 1, column 1:
+      from p
+      ~~~~~~
       test: pool not found at line 1, column 6:
       from test
            ~~~~