CC @griesemer

Note the documentation in the tabwriter package:

A Writer is a filter that inserts padding around tab-delimited columns in its input to align them in the output. (https://golang.org/pkg/text/tabwriter/)

If you delimit (rather than separate) the colums with tabs it does what you want:

package main

import (
        "fmt"
        "os"
        "text/tabwriter"
)

func main() {
        flags := tabwriter.AlignRight | tabwriter.Debug
        w := tabwriter.NewWriter(os.Stderr, 0, 0, 1, '.', flags)
        fmt.Fprintln(w, "a\tb\tc\t")     // <<<<<< delimiting tab at end
        fmt.Fprintln(w, "aa\tbb\tcc\t")  // <<<<<< delimiting tab at end
        w.Flush()
}

And the output is:

..a|..b|..c|
.aa|.bb|.cc|

This is working as intended. Closing.

@griesemer, thank you for clarifying. Perhaps this needs a documentation update, since the tabwriter documentation says this:

The Writer treats incoming bytes as UTF-8 encoded text consisting of cells terminated by (horizontal or vertical) tabs or line breaks (newline or formfeed characters). Cells in adjacent lines constitute a column.

Cells can be terminated by line breaks; I'd think that the line breaks after the right-most column in my example code would have led tabwriter to interpret that last column as align-able.

Should the documentation be updated to say that the cells can only be terminated by horizontal or vertical tabs? I might still be misinterpreting.

@spenczar Fair enough. But then read further:

Note that cells are tab-terminated, not tab-separated: trailing non-tab text at the end of a line does not form a column cell.

This is emphasized twice. That said, I agree that this does appear to contradict the former sentence. I'll update the doc.

CL https://golang.org/cl/19855 mentions this issue.

Thank you - I really appreciate the work on docs, boring as it may be. The examples make this sparklingly clear now.