testing: test output indentation looks inconsistent when tab width != 4

[dpinela]

What did you do?

Run the following program:
https://play.golang.org/p/IAMobZmXMqw

What did you expect to see?

=== RUN   TestX
=== RUN   TestX/Y
=== RUN   TestX/Y/Z
--- FAIL: TestX (0.00s)
    main.go:6: 1
    --- FAIL: TestX/Y (0.00s)
        main.go:8: 2
        --- FAIL: TestX/Y/Z (0.00s)
            main.go:10: 3
    main.go:13: 4
FAIL

This is what you see if tabs are 4 spaces wide. Note that each subtest's output is indented with 4 leading spaces, and each log message has a tab after those.

What did you see instead?

=== RUN   TestX
=== RUN   TestX/Y
=== RUN   TestX/Y/Z
--- FAIL: TestX (0.00s)
        main.go:6: 1
    --- FAIL: TestX/Y (0.00s)
        main.go:8: 2
        --- FAIL: TestX/Y/Z (0.00s)
                main.go:10: 3
        main.go:13: 4
FAIL

This is what you see if tabs are 8 spaces wide; any tab width other than 4 will cause similar inconsistencies.

System details

go version go1.10.2 darwin/amd64
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/dpinela/Library/Caches/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/dpinela/dev/go"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.10.2/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.10.2/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/41/2xpv_r1j5n5bnflwb7s1hv580000gp/T/go-build030076165=/tmp/go-build -gno-record-gcc-switches -fno-common"
GOROOT/bin/go version: go version go1.10.2 darwin/amd64
GOROOT/bin/go tool compile -V: compile version go1.10.2
uname -v: Darwin Kernel Version 17.5.0: Fri Apr 13 19:32:32 PDT 2018; root:xnu-4570.51.2~1/RELEASE_X86_64
ProductName:	Mac OS X
ProductVersion:	10.13.4
BuildVersion:	17E202
lldb --version: lldb-902.0.79.2
  Swift-4.1

[ysmolsky]

Indeed, there is a mix of tabs and 4 spaces indentations in testing package. I am not sure what was the purpose of tabs in indentation of every line since we have 4 spaces here: https://github.com/golang/go/blob/master/src/testing/testing.go#L429

A quick fix comes to mind:

diff --git a/src/testing/testing.go b/src/testing/testing.go
index 573ef05fdc..ee3bebb7ba 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -381,7 +381,7 @@ func (c *common) decorate(s string) string {
        }
        buf := new(strings.Builder)
        // Every line is indented at least one tab.
-       buf.WriteByte('\t')
+       buf.WriteString("    ")
        fmt.Fprintf(buf, "%s:%d: ", file, line)
        lines := strings.Split(s, "\n")
        if l := len(lines); l > 1 && lines[l-1] == "" {

But it implies fixing tests as well.

[gopherbot]

Change https://golang.org/cl/113177 mentions this issue: testing: make indentation consistent in sub-tests

[ysmolsky]

I wonder if this change can break others programs or some Golang promises.
ping @andybons @bradfitz

[andybons]

I think it’s fine. If someone is relying on the textual output of tests instead of using the JSON output, then this will be a good reason for them to switch :)