cmd/go: report scan error position in 'go list -e'tls

This CL extracts some error handling code into a common method for
presenting errors encountered when loading package data.

Fixes #36087
Fixes #36762

Change-Id: I87c8d41e3cc6e6afa152d9c067bc60923bf19fbe
Reviewed-on: https://go-review.googlesource.com/c/go/+/210938
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

1 files changed, 0 insertions, 25 deletions

diff --git a/src/cmd/go/internal/base/base.go b/src/cmd/go/internal/base/base.go
index 272da55681..ab2f1bb4e2 100644
--- a/src/cmd/go/internal/base/base.go
+++ b/src/cmd/go/internal/base/base.go
@@ -7,11 +7,8 @@
 package base
 
 import (
-	"bytes"
-	"errors"
 	"flag"
 	"fmt"
-	"go/scanner"
 	"log"
 	"os"
 	"os/exec"
@@ -172,25 +169,3 @@ func RunStdin(cmdline []string) {
 // Usage is the usage-reporting function, filled in by package main
 // but here for reference by other packages.
 var Usage func()
-
-// ExpandScanner expands a scanner.List error into all the errors in the list.
-// The default Error method only shows the first error
-// and does not shorten paths.
-func ExpandScanner(err error) error {
-	// Look for parser errors.
-	if err, ok := err.(scanner.ErrorList); ok {
-		// Prepare error with \n before each message.
-		// When printed in something like context: %v
-		// this will put the leading file positions each on
-		// its own line. It will also show all the errors
-		// instead of just the first, as err.Error does.
-		var buf bytes.Buffer
-		for _, e := range err {
-			e.Pos.Filename = ShortPath(e.Pos.Filename)
-			buf.WriteString("\n")
-			buf.WriteString(e.Error())
-		}
-		return errors.New(buf.String())
-	}
-	return err
-}