fix(output): always report warnings on stderr

Signed-off-by: bircni <bircni@icloud.com>

docs/migration-1.0.md

@@ -298,7 +298,8 @@ of printing nothing. See `tea help formatting`.
 When stdout is not a terminal, lists print tab-separated values without header,
 color or links, with times in RFC 3339 UTC, and a `--page` hint goes to stderr;
 prefer `--json` in scripts. Commands that change resources report each change on
-stderr only on a terminal. Create commands print the URL of the new resource on
+stderr only on a terminal; warnings, such as a step that was skipped or failed,
+always go to stderr. Create commands print the URL of the new resource on
 stdout, so `url=$(tea issue create …)` works; other changes print nothing when
 piped. Bodies are rendered as Markdown only on a terminal (`tea config set
 markdown raw` turns this off). See `tea help formatting` for the terminal layout.

internal/app/human_output.go

@@ -133,19 +133,20 @@ func writeView[T any](a *application, cmd *cobra.Command, item T, view func(T) t
 // done reports a completed mutation on stderr, such as "✓ Closed issue alice/x#5 (Fix login)",
 // when people read stdout: on a TTY and without --json.
 func (a *application) done(cmd *cobra.Command, format string, args ...any) {
+	if !a.deps.Streams.OutTTY || a.options.json != "" {
+		return
+	}
 	a.feedback(cmd, "✓", "green", format, args...)
 }
 
-// warn reports a mutation that had nothing to do, such as "! Issue alice/x#5 (Fix login) is already
+// warn reports on stderr a mutation that had nothing to do, such as "! Issue alice/x#5 (Fix login)
-// closed", under the same conditions as done.
+// is already closed", or a part of one that failed. Unlike done it is never silenced, so scripts
+// and --json callers still learn about partial failures.
 func (a *application) warn(cmd *cobra.Command, format string, args ...any) {
 	a.feedback(cmd, "!", "yellow", format, args...)
 }
 
 func (a *application) feedback(cmd *cobra.Command, icon, color, format string, args ...any) {
-	if !a.deps.Streams.OutTTY || a.options.json != "" {
-		return
-	}
 	fmt.Fprintln(cmd.ErrOrStderr(), terminal.Colorize(color, icon, a.colorEnabled())+" "+terminal.SafeLine(fmt.Sprintf(format, args...)))
 }
 

internal/app/human_output_test.go

@@ -359,8 +359,8 @@ func TestMutationFeedback(t *testing.T) {
 		tty                     bool
 	}{
 		{name: "terminal", tty: true, out: "https://example.org/12\n", stderr: "✓ Created issue alice/x#12 (Fix[2J login)\n! Issue alice/x#12 (Fix[2J login) is already closed\n"},
-		{name: "piped", out: "https://example.org/12\n"},
+		{name: "piped", out: "https://example.org/12\n", stderr: "! Issue alice/x#12 (Fix[2J login) is already closed\n"},
-		{name: "JSON", tty: true, json: "number"},
+		{name: "JSON", tty: true, json: "number", stderr: "! Issue alice/x#12 (Fix[2J login) is already closed\n"},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			deps, out, diagnostics := testDeps(t)