sysupdate(flatpak): list updates when one needs an uninstalled runtime

Fixes #3950
Port 2.0

(cherry picked from commit a7bd6a8e06)

core/internal/server/sysupdate/backend_flatpak.go

@@ -3,6 +3,7 @@ package sysupdate
 import (
 	"context"
 	"errors"
+	"fmt"
 	"os/exec"
 	"strings"
 )
@@ -21,18 +22,21 @@ func (flatpakBackend) RunsInTerminal() bool               { return false }
 func (flatpakBackend) IsAvailable(_ context.Context) bool { return commandExists("flatpak") }
 
 func (flatpakBackend) CheckUpdates(ctx context.Context) ([]Package, error) {
-	// Run `flatpak update`
-	cmd := exec.CommandContext(ctx, "flatpak", "update")
+	// Without --no-deps an update needing an uninstalled runtime prompts first, and declining aborts before the table prints.
+	cmd := exec.CommandContext(ctx, "flatpak", "update", "--no-deps")
 	cmd.Stdin = strings.NewReader("n\nn\n") // decline up to 2 installation prompts
 	out, err := cmd.Output()
-	if err != nil {
-		if exitErr, ok := errors.AsType[*exec.ExitError](err); ok && exitErr.ExitCode() == 1 && len(out) > 0 {
-		} else if len(out) == 0 {
-			return nil, err
+	pkgs := parseFlatpakUpdateOutput(string(out), flatpakInstalled(ctx))
+	// Declining the final prompt also exits non-zero, so only a failure without a table is an error.
+	if err != nil && len(pkgs) == 0 {
+		if exitErr, ok := errors.AsType[*exec.ExitError](err); ok {
+			if msg := lastNonEmptyLine(string(exitErr.Stderr)); msg != "" {
+				return nil, fmt.Errorf("flatpak update: %s", msg)
+			}
 		}
+		return nil, err
 	}
-	installed := flatpakInstalled(ctx)
-	return parseFlatpakUpdateOutput(string(out), installed), nil
+	return pkgs, nil
 }
 
 type flatpakInstalledEntry struct {

core/internal/server/sysupdate/backend_flatpak_test.go

@@ -2,6 +2,7 @@ package sysupdate
 
 import (
 	"reflect"
+	"strings"
 	"testing"
 )
 
@@ -100,3 +101,47 @@ func TestParseFlatpakUpdateOutput(t *testing.T) {
 		})
 	}
 }
+
+func TestFlatpakCheckUpdates(t *testing.T) {
+	const runtimePrompt = `[ "$1" = list ] && exit 0
+for a in "$@"; do
+	if [ "$a" = --no-deps ]; then
+		printf ' 1.\tVesktop\tdev.vencord.Vesktop\tstable\tu\tflathub\t< 130 MB\n\nProceed with these changes? [Y/n]: '
+		exit 1
+	fi
+done
+printf 'Required runtime for dev.vencord.Vesktop/x86_64/stable found in remote flathub\nDo you want to install it? [Y/n]: '
+echo 'error: The application dev.vencord.Vesktop/x86_64/stable requires the runtime org.freedesktop.Platform/x86_64/26.08 which is not installed' >&2
+exit 1`
+
+	for _, tt := range []struct {
+		name    string
+		script  string
+		wantRef string
+		wantErr string
+	}{
+		{name: "update needing a new runtime", script: runtimePrompt, wantRef: "dev.vencord.Vesktop//stable"},
+		{
+			name:    "failure without a table",
+			script:  "[ \"$1\" = list ] && exit 0\necho 'Looking for updates…'\necho 'error: Unable to load summary from remote flathub' >&2\nexit 1",
+			wantErr: "Unable to load summary",
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			dir := t.TempDir()
+			t.Setenv("PATH", dir)
+			writeUpdateExecutable(t, dir, "flatpak", tt.script)
+
+			pkgs, err := flatpakBackend{}.CheckUpdates(t.Context())
+			if tt.wantErr != "" {
+				if err == nil || !strings.Contains(err.Error(), tt.wantErr) {
+					t.Errorf("err = %v, want %q (a failed check must not read as up to date)", err, tt.wantErr)
+				}
+				return
+			}
+			if err != nil || len(pkgs) != 1 || pkgs[0].Ref != tt.wantRef {
+				t.Errorf("pkgs = %#v, err = %v, want %s", pkgs, err, tt.wantRef)
+			}
+		})
+	}
+}