Files
mesh-controller/cmd/mesh-builder/stdout_test.go
jschoubben 2fb700d61b Builder diagnostics go to stderr; stdout is the result alone
The logging added a line to stdout, and the genesis path parses the builder's
stdout as JSON — so the first log line broke the parse with "invalid character
'c'", the c from "[clone]". A build that had worked stopped working because of a
print statement.

The installer's runner captures stdout alone (cmd.Output), and the contract was
already stdout=result, stderr=everything else. The fix is to honour it: every
builder diagnostic — the step log, the per-command echo, the module path's own
lines — goes to stderr. Stdout carries only once.go's result JSON.

And a unit test now fails if any fmt.Print to stdout appears in the two builder
command files, except the three that belong there: the result, --version, and
--help. A guard, because this was invisible until a 20-minute run hit it, and the
same class of mistake should fail in milliseconds next time.

Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx
2026-09-15 23:01:04 +02:00

45 lines
1.3 KiB
Go

package main
import (
"os"
"strings"
"testing"
)
// **The genesis path writes its result to stdout and nothing else there.** The installer captures
// stdout alone and parses it as JSON; one stray log line makes that fail with "invalid character"
// — exactly what a builder fmt.Printf caused, breaking a build that had worked. This keeps
// diagnostics on stderr so a future print cannot repeat it silently.
func TestBuilderDiagnosticsStayOffStdout(t *testing.T) {
allowed := map[string]bool{
"string(body)": true, // once.go: the result JSON, which IS stdout
"version)": true, // --version
`"stopping")`: true, // the loop.s shutdown line
"usage)": true, // --help text, for a human
}
for _, file := range []string{"once.go", "main.go"} {
src, err := os.ReadFile(file)
if err != nil {
t.Fatal(err)
}
for i, raw := range strings.Split(string(src), "\n") {
line := strings.TrimSpace(raw)
if !strings.HasPrefix(line, "fmt.Printf(") &&
!strings.HasPrefix(line, "fmt.Println(") &&
!strings.HasPrefix(line, "fmt.Print(") {
continue
}
ok := false
for token := range allowed {
if strings.Contains(line, token) {
ok = true
}
}
if !ok {
t.Errorf("%s:%d writes a diagnostic to stdout, which the installer parses as JSON:\n %s",
file, i+1, line)
}
}
}
}