pkg/storage: expose os.Stderr's Close and ReadAt methods (#6338)

StdinEngine.Get wraps os.Stderr with io.NopCloser and
notSupportedReaderAt to hide its Close and ReadAt methods.  This doesn't
appear to be necessary, and exposing ReadAt enables reading CSUP and
Parquet files from standard input.

Author: nwt

pkg/storage/stdio.go

@@ -20,7 +20,7 @@ func (*StdioEngine) Get(_ context.Context, u *URI) (Reader, error) {
 	if u.Scheme != "stdio" || (u.Path != "stdin" && u.Path != "") {
 		return nil, fmt.Errorf("cannot read from %q", u)
 	}
-	return &notSupportedReaderAt{io.NopCloser(os.Stdin)}, nil
+	return os.Stdin, nil
 }
 
 func (*StdioEngine) Put(ctx context.Context, u *URI) (io.WriteCloser, error) {

sio/anyio/ztests/csup.yaml

@@ -1,12 +1,17 @@
 script: |
   super -f csup -o f -
   super -s f
+  echo // standard input
+  super -s -c 'from "stdio:stdin"' < f
 
 inputs:
   - name: stdin
-    data: &stdin |
+    data: |
       {a:1}
 
 outputs:
   - name: stdout
-    data: *stdin
+    data: |
+      {a:1}
+      // standard input
+      {a:1}

sio/anyio/ztests/parquet.yaml

@@ -1,12 +1,17 @@
 script: |
   super -f parquet -o f -
   super -s f
+  echo // standard input
+  super -s -c 'from "stdio:stdin"' < f
 
 inputs:
   - name: stdin
-    data: &stdin |
+    data: |
       {a:1}
 
 outputs:
   - name: stdout
-    data: *stdin
+    data: |
+      {a:1}
+      // standard input
+      {a:1}