fix: keep human-readable output off stdout in --json mode

src/pkg/cli/compose/loader.go

@@ -175,7 +175,7 @@ func (l *Loader) loadProject(ctx context.Context, suppressWarn bool) (*Project,
 
 	if term.DoDebug() {
 		b, _ := yaml.Marshal(project)
-		term.Println(string(b))
+		term.Println(string(b)) // term.Println routes to stderr in JSON mode, so this never corrupts --json stdout
 	}
 
 	l.cached = project

src/pkg/cli/compose/loader_test.go

@@ -38,6 +38,44 @@ func TestResolveProjectWorkingDirDoesNotLoadOrCacheProject(t *testing.T) {
 	assert.Equal(t, dir, workingDir)
 }
 
+// TestLoadProjectDebugDumpNeverHitsStdoutInJSONMode is a regression test:
+// `defang services --json` with DEFANG_DEBUG=1 used to write the project's
+// YAML dump to stdout ahead of the JSON payload, corrupting it for callers
+// like `defang-github-action`'s deployment summary (jq: invalid numeric
+// literal). term.Println now routes to stderr in JSON mode, so the dump
+// must never appear on stdout, whether or not JSON mode is on.
+func TestLoadProjectDebugDumpNeverHitsStdoutInJSONMode(t *testing.T) {
+	dir := t.TempDir()
+	composePath := filepath.Join(dir, "compose.yaml")
+	require.NoError(t, os.WriteFile(composePath, []byte("services:\n  web:\n    image: alpine\n"), 0o644))
+
+	oldTerm := term.DefaultTerm
+	t.Cleanup(func() { term.DefaultTerm = oldTerm })
+
+	t.Run("debug alone dumps the project to stdout", func(t *testing.T) {
+		var stdout, stderr bytes.Buffer
+		term.DefaultTerm = term.NewTerm(os.Stdin, &stdout, &stderr)
+		term.DefaultTerm.SetDebug(true)
+
+		_, err := NewLoader(WithPath(composePath)).LoadProject(t.Context())
+		require.NoError(t, err)
+		assert.Contains(t, stdout.String(), "services:")
+		assert.Empty(t, stderr.String())
+	})
+
+	t.Run("debug plus json moves the dump to stderr", func(t *testing.T) {
+		var stdout, stderr bytes.Buffer
+		term.DefaultTerm = term.NewTerm(os.Stdin, &stdout, &stderr)
+		term.DefaultTerm.SetDebug(true)
+		term.DefaultTerm.SetJSON(true)
+
+		_, err := NewLoader(WithPath(composePath)).LoadProject(t.Context())
+		require.NoError(t, err)
+		assert.Empty(t, stdout.String())
+		assert.Contains(t, stderr.String(), "services:")
+	})
+}
+
 func TestResolveProjectWorkingDirDoesNotSuppressProjectWarnings(t *testing.T) {
 	dir := t.TempDir()
 	composePath := filepath.Join(dir, "compose.yaml")

src/pkg/term/colorizer.go

@@ -195,20 +195,24 @@ func ensurePrefix(prefix prefixChars, s string) string {
 	return string(prefix) + s
 }
 
+// Printc, Print, Println, and Printf are for human-readable text; they write
+// to stderr instead of stdout when JSON mode is on, so they never corrupt a
+// command's --json payload. The only thing that belongs on stdout in JSON
+// mode is the JSON payload itself (see jsonTable in table.go).
 func (t *Term) Printc(c Color, v ...any) (int, error) {
-	return output(t.out, c, fmt.Sprint(v...))
+	return output(t.outOrErr(), c, fmt.Sprint(v...))
 }
 
 func (t *Term) Print(v ...any) (int, error) {
-	return fmt.Fprint(t.out, v...)
+	return fmt.Fprint(t.outOrErr(), v...)
 }
 
 func (t *Term) Println(v ...any) (int, error) {
-	return fmt.Fprintln(t.out, v...)
+	return fmt.Fprintln(t.outOrErr(), v...)
 }
 
 func (t *Term) Printf(format string, v ...any) (int, error) {
-	return fmt.Fprintf(t.out, format, v...)
+	return fmt.Fprintf(t.outOrErr(), format, v...)
 }
 
 func (t *Term) Debug(v ...any) (int, error) {

src/pkg/term/colorizer_test.go

@@ -162,6 +162,35 @@ func TestIsTerminal(t *testing.T) {
 		t.Error("Expected IsTerminal() to return false")
 	}
 }
+
+// TestPrintRoutingInJSONMode is a regression test: Print/Println/Printf/Printc
+// used to always write to stdout, so any of them reachable from a command
+// that also emits --json output (e.g. via a debug dump) would corrupt that
+// JSON payload. They must move to stderr in JSON mode, like Info/Warn do.
+func TestPrintRoutingInJSONMode(t *testing.T) {
+	var stdout, stderr bytes.Buffer
+	defaultTerm := NewTerm(os.Stdin, &stdout, &stderr)
+
+	defaultTerm.Print("a")
+	defaultTerm.Println("b")
+	defaultTerm.Printf("%s", "c")
+	defaultTerm.Printc(InfoColor, "d")
+	if stdout.String() == "" || stderr.String() != "" {
+		t.Errorf("expected Print* to write to stdout when JSON mode is off; stdout=%q stderr=%q", stdout.String(), stderr.String())
+	}
+
+	stdout.Reset()
+	stderr.Reset()
+	defaultTerm.SetJSON(true)
+
+	defaultTerm.Print("a")
+	defaultTerm.Println("b")
+	defaultTerm.Printf("%s", "c")
+	defaultTerm.Printc(InfoColor, "d")
+	if stdout.String() != "" || stderr.String() == "" {
+		t.Errorf("expected Print* to write to stderr when JSON mode is on; stdout=%q stderr=%q", stdout.String(), stderr.String())
+	}
+}
 func TestWarn(t *testing.T) {
 	tests := []struct {
 		msgs     []string