fix(ui): decide colour per output stream

scripts/regressions/stdout-color-decided-from-stderr-tty.sh

@@ -0,0 +1,114 @@
+#!/usr/bin/env bash
+# Regression: commands that write their colourised rows to stdout decided
+# whether to colour by probing *stderr*. Run from a terminal with stdout
+# redirected - `mt info jq > out.txt` - and raw ANSI landed in the file.
+#
+# Only a real terminal on stderr can reproduce it, so the run happens under
+# script(1): the child gets a pty, and the inner redirect sends stdout to a
+# file while stderr stays on the pty. That is the exact user-facing shape.
+#
+# The second half proves the forced policy still reaches the stdout path:
+# CLICOLOR_FORCE=1 must colourise even when stdout is a plain file.
+#
+# Hermetic: a seeded keg in a throwaway prefix, MALT_OFFLINE=1, no network.
+#
+# Usage: scripts/regressions/stdout-color-decided-from-stderr-tty.sh
+# Requirements: built `malt` at $MALT_BIN or zig-out/bin/malt, sqlite3 on PATH.
+
+set -euo pipefail
+
+ROOT=$(cd "$(dirname "$0")/../.." && pwd)
+BIN="${MALT_BIN:-$ROOT/zig-out/bin/malt}"
+[[ -x "$BIN" ]] || {
+  echo "build malt first: zig build" >&2
+  exit 2
+}
+command -v sqlite3 >/dev/null 2>&1 || {
+  echo "this regression needs sqlite3 on PATH" >&2
+  exit 2
+}
+
+PREFIX="$(mktemp -d)"
+OUTDIR="$PREFIX/out"
+mkdir -p "$PREFIX/db" "$OUTDIR"
+export MALT_PREFIX="$PREFIX"
+export MALT_NO_EMOJI=1
+export MALT_OFFLINE=1
+trap 'rm -rf "$PREFIX"' EXIT
+
+pass() { printf '  \xe2\x9c\x93 %s\n' "$*"; }
+fail() {
+  printf '  \xe2\x9c\x97 %s\n' "$*" >&2
+  exit 1
+}
+
+ESC=$'\033['
+
+DB="$PREFIX/db/malt.db"
+
+# Let malt bootstrap the schema, then seed one keg plus the bin symlink
+# `mt which` resolves through.
+"$BIN" list --quiet >/dev/null 2>&1 || true
+[[ -f "$DB" ]] || fail "DB was not initialised by mt list"
+sqlite3 "$DB" <<SQL
+INSERT INTO kegs (name, full_name, version, revision, store_sha256, cellar_path, install_reason)
+VALUES ('jq', 'jq', '1.7.1', 0, 'sha_jq', '$PREFIX/Cellar/jq/1.7.1', 'direct');
+-- A dependent, so \`mt uses jq\` renders a real row instead of the empty notice.
+INSERT INTO kegs (name, full_name, version, revision, store_sha256, cellar_path, install_reason)
+VALUES ('gojq', 'gojq', '0.12.0', 0, 'sha_gojq', '$PREFIX/Cellar/gojq/0.12.0', 'direct');
+INSERT INTO dependencies (keg_id, dep_name, dep_type)
+SELECT id, 'jq', 'runtime' FROM kegs WHERE name = 'gojq';
+SQL
+mkdir -p "$PREFIX/Cellar/jq/1.7.1/bin" "$PREFIX/bin"
+: >"$PREFIX/Cellar/jq/1.7.1/bin/jq"
+ln -s "$PREFIX/Cellar/jq/1.7.1/bin/jq" "$PREFIX/bin/jq"
+
+# Every subcommand here builds a stdout writer and styles what it writes.
+CMDS=(
+  "info jq"
+  "which jq"
+  "list"
+  "search --installed jq"
+  "uses jq"
+)
+
+slug() { printf '%s' "$1" | tr -c 'a-z0-9' '_'; }
+
+# script(1) hands the child a fresh pty and records it; the inner `>` peels
+# stdout off that pty, leaving stderr on it. shellcheck cannot see the inner
+# expansion.
+# shellcheck disable=SC2016
+run_under_pty() {
+  local cmd="$1" out="$2" tty_log="$3"
+  MT_BIN="$BIN" MT_CMD="$cmd" MT_OUT="$out" \
+    script -q "$tty_log" sh -c '$MT_BIN $MT_CMD >"$MT_OUT"' </dev/null >/dev/null 2>&1 || true
+}
+
+for cmd in "${CMDS[@]}"; do
+  out="$OUTDIR/$(slug "$cmd").txt"
+  run_under_pty "$cmd" "$out" /dev/null
+  [[ -s "$out" ]] || fail "mt $cmd wrote nothing to the redirected stdout"
+  grep -qF "$ESC" "$out" &&
+    fail "mt $cmd leaked ANSI into a redirected stdout (stderr was the terminal)"
+  pass "mt $cmd: redirected stdout stayed plain"
+done
+
+# The other half of the divergence, and the reason the checks above are not
+# vacuous: in the same run, stderr is still a terminal and must KEEP its
+# colour. Without this, silencing colour on both streams would pass.
+run_under_pty "which definitely-not-installed" "$OUTDIR/miss.txt" "$OUTDIR/miss.tty"
+grep -qF "$ESC" "$OUTDIR/miss.tty" ||
+  fail "stderr lost its colour while stdout was redirected; both streams went plain"
+pass "stderr kept its colour in the same run"
+
+# The forced policy is stream-independent: no terminal anywhere, colour anyway.
+for cmd in "${CMDS[@]}"; do
+  out="$OUTDIR/forced_$(slug "$cmd").txt"
+  # shellcheck disable=SC2086 # $cmd carries its own arguments; splitting is the point
+  CLICOLOR_FORCE=1 "$BIN" $cmd >"$out" 2>/dev/null || true
+  grep -qF "$ESC" "$out" ||
+    fail "CLICOLOR_FORCE=1 did not colourise mt $cmd on a piped stdout"
+  pass "mt $cmd: CLICOLOR_FORCE=1 colourised the redirected stdout"
+done
+
+printf '\n\xe2\x9c\x94 stdout colour follows the stdout stream\n'

src/cli/doctor.zig

@@ -586,7 +586,7 @@ pub fn emitFixHintIfNeeded(fix_requested: bool) void {
 fn writeStyledDetail(text: []const u8) void {
     var line_buf: [1024]u8 = undefined;
     const line = std.fmt.bufPrint(&line_buf, "    - {s}\n", .{text}) catch return;
-    if (color.isColorEnabled()) {
+    if (color.isColorEnabledForStderr()) {
         output.writeStderrAll(color.SemanticStyle.detail.code());
         output.writeStderrAll(line);
         output.writeStderrAll(color.Style.reset.code());

src/cli/doctor/render.zig

@@ -189,7 +189,7 @@ pub fn printCheck(name: []const u8, status: CheckStatus, detail: ?[]const u8) vo
     var w: std.Io.Writer = .fixed(&buf);
     // Truncation of an oversized row is acceptable - `buffered()` still emits what fit.
     renderCheckRow(&w, status, name, detail, .{
-        .color = color.isColorEnabled(),
+        .color = color.isColorEnabledForStderr(),
         .emoji = color.isEmojiEnabled(),
     }) catch {};
     output.writeStderrAll(w.buffered());

src/cli/info.zig

@@ -87,7 +87,7 @@ pub fn execute(ctx: *const AppCtx, allocator: std.mem.Allocator, args: []const [
     // Flush on teardown; stdout closed by a broken pipe is normal shell usage.
     defer stdout.flush() catch {};
 
-    const colorize = !json_mode and color.isColorEnabled();
+    const colorize = !json_mode and color.isColorEnabledFor(.stdout);
 
     // `--cask`/`--formula` are inclusive selectors, like `search`: each
     // flag opts its kind in, and "both set" reads the same as "neither set"

src/cli/list.zig

@@ -295,7 +295,7 @@ fn pinnedUnionSql(show_formula: bool, show_cask: bool, tap_filter: bool) ?[:0]co
 
 /// Emit the leading cyan bullet + space, honouring `NO_COLOR`.
 fn writeBulletPrefix(stdout: *std.Io.Writer) void {
-    if (color.isColorEnabled()) {
+    if (color.isColorEnabledFor(.stdout)) {
         stdout.writeAll(color.SemanticStyle.info.code()) catch return;
         stdout.writeAll("  ▸ ") catch return;
         stdout.writeAll(color.Style.reset.code()) catch return;
@@ -313,7 +313,7 @@ fn writeStyledSpan(
     body: []const u8,
     close: []const u8,
 ) void {
-    const use_color = color.isColorEnabled();
+    const use_color = color.isColorEnabledFor(.stdout);
     if (use_color) stdout.writeAll(style_code) catch return;
     stdout.writeAll(open) catch return;
     stdout.writeAll(body) catch return;

src/cli/migrate.zig

@@ -501,7 +501,7 @@ fn emitBrewUninstallHint(
     var line: std.ArrayList(u8) = .empty;
     defer line.deinit(allocator);
 
-    const use_color = color.isColorEnabled();
+    const use_color = color.isColorEnabledForStderr();
     const prefix: []const u8 = if (color.isEmojiEnabled()) "  ▸ " else "  > ";
     if (use_color) try line.appendSlice(allocator, color.SemanticStyle.detail.code());
     try line.appendSlice(allocator, prefix);

src/cli/outdated/render.zig

@@ -85,7 +85,7 @@ pub fn writeJsonArray(
 /// Match the `mt list` / `mt search` row shape: cyan bullet, plain
 /// name, dimmed `(installed)`, warn-coloured `≠ latest`, and an
 /// optional dim `[kind]` tag for casks. Honours `NO_COLOR` / pipes
-/// automatically via `color.isColorEnabled()`.
+/// automatically via `color.isColorEnabledFor(.stdout)`.
 fn writeEntry(stdout: *std.Io.Writer, e: OutdatedEntry, kind_tag: ?[]const u8) void {
     if (output.isQuiet()) {
         stdout.writeAll(e.name) catch return;
@@ -112,7 +112,7 @@ fn isDowngrade(installed: []const u8, latest: []const u8) bool {
 }
 
 fn writeBullet(stdout: *std.Io.Writer) void {
-    if (color.isColorEnabled()) {
+    if (color.isColorEnabledFor(.stdout)) {
         stdout.writeAll(color.SemanticStyle.info.code()) catch return;
         stdout.writeAll("  \xe2\x96\xb8 ") catch return;
         stdout.writeAll(color.Style.reset.code()) catch return;
@@ -128,7 +128,7 @@ fn writeStyledSpan(
     body: []const u8,
     close: []const u8,
 ) void {
-    const use_color = color.isColorEnabled();
+    const use_color = color.isColorEnabledFor(.stdout);
     if (use_color) stdout.writeAll(style_code) catch return;
     stdout.writeAll(open) catch return;
     stdout.writeAll(body) catch return;

src/cli/purge/report.zig

@@ -129,7 +129,7 @@ pub const Reporter = struct {
 fn writeItem(text: []const u8) void {
     if (output.isQuiet()) return; // raw stderr writes don't honour --quiet on their own
     const bullet: []const u8 = if (color.isEmojiEnabled()) "    • " else "    - ";
-    if (color.isColorEnabled()) {
+    if (color.isColorEnabledForStderr()) {
         output.writeStderrAll(color.SemanticStyle.detail.code());
         output.writeStderrAll(bullet);
         output.writeStderrAll(color.Style.reset.code());
@@ -148,7 +148,7 @@ fn writeMore(remaining: usize) void {
         "    … {d} more (use --verbose to show all)",
         .{remaining},
     ) catch return;
-    if (color.isColorEnabled()) {
+    if (color.isColorEnabledForStderr()) {
         output.writeStderrAll(color.SemanticStyle.detail.code());
         output.writeStderrAll(msg);
         output.writeStderrAll(color.Style.reset.code());
@@ -190,10 +190,10 @@ fn writeRule() void {
     if (output.isQuiet()) return;
     var buf: [rule_width]u8 = undefined;
     @memset(buf[0..], '-');
-    if (color.isColorEnabled()) output.writeStderrAll(color.SemanticStyle.detail.code());
+    if (color.isColorEnabledForStderr()) output.writeStderrAll(color.SemanticStyle.detail.code());
     output.writeStderrAll("  ");
     output.writeStderrAll(buf[0..rule_width]);
-    if (color.isColorEnabled()) output.writeStderrAll(color.Style.reset.code());
+    if (color.isColorEnabledForStderr()) output.writeStderrAll(color.Style.reset.code());
     output.writeStderrAll("\n");
 }
 

src/cli/rollback.zig

@@ -557,7 +557,7 @@ fn printListing(
     if (output.isJson()) {
         try writeListJson(&aw.writer, name, entries);
     } else {
-        try writeListHuman(&aw.writer, name, entries, color.isColorEnabled());
+        try writeListHuman(&aw.writer, name, entries, color.isColorEnabledFor(.stdout));
     }
     output.writeStdoutAll(aw.written());
 }

src/cli/search.zig

@@ -986,7 +986,7 @@ test "loadInstalledKind returns every installed name for the kind, sorted" {
 
 /// Write a single search result with the same ▸ prefix style used by `list`.
 fn writeResult(stdout: *std.Io.Writer, name: []const u8, kind: []const u8) void {
-    const use_color = color.isColorEnabled();
+    const use_color = color.isColorEnabledFor(.stdout);
     if (use_color) stdout.writeAll(color.SemanticStyle.info.code()) catch return;
     stdout.writeAll("  \xe2\x96\xb8 ") catch return;
     if (use_color) stdout.writeAll(color.Style.reset.code()) catch return;

src/cli/uses.zig

@@ -153,7 +153,7 @@ pub fn writeHuman(stdout: *std.Io.Writer, target: []const u8, dependents: [][]co
         stdout.writeAll(line) catch return;
         return;
     }
-    const use_color = color.isColorEnabled();
+    const use_color = color.isColorEnabledFor(.stdout);
     for (dependents) |d| {
         if (use_color) stdout.writeAll(color.SemanticStyle.info.code()) catch return;
         stdout.writeAll("  \xe2\x96\xb8 ") catch return;

src/cli/which.zig

@@ -129,7 +129,7 @@ pub fn execute(ctx: *const AppCtx, _: std.mem.Allocator, args: []const []const u
     if (output.isJson()) {
         try encodeJson(stdout, res);
     } else {
-        try encodeHuman(stdout, res, color.isColorEnabled());
+        try encodeHuman(stdout, res, color.isColorEnabledFor(.stdout));
     }
 }