From a539d7d968e36640df04545df519034602e3ca85 Mon Sep 17 00:00:00 2001
From: Weimin Yu <weiminyu@google.com>
Date: Tue, 14 Jul 2026 16:46:38 -0400
Subject: [PATCH] Avoid outputting garbage sequences in Nomulus CLI

Lazy-initialize the terminal and LineReader in ShellCommand to prevent JLine from eagerly probing terminal capabilities during JCommander command-line startup.

During CLI startup, JCommander instantiates every command (including ShellCommand) to build the CLI's command map. Eager instantiation of the LineReader inside the ShellCommand constructor causes JLine to query the terminal cursor via Device Status Report (DSR) escape sequences. Standard commands (e.g. list_tlds) do not consume stdin, leaving these probing responses (such as ^[[71;1R and 1;1R) in the buffer to be leaked as garbage characters to standard output.

This change defers terminal and LineReader initialization until the shell's run() method is actually executed, while preserving the original constructor for unit tests.

BUG=http://b/534855218
---
 .../google/registry/tools/ShellCommand.java   | 34 ++++++++++++++-----
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/core/src/main/java/google/registry/tools/ShellCommand.java b/core/src/main/java/google/registry/tools/ShellCommand.java
index 156abdad885..918d0afc479 100644
--- a/core/src/main/java/google/registry/tools/ShellCommand.java
+++ b/core/src/main/java/google/registry/tools/ShellCommand.java
@@ -91,10 +91,11 @@ public class ShellCommand implements Command {
    * flags aren't available in the constructor, so we have to do it in the {@link #run} function.
    */
   private final CommandRunner originalRunner;
-
-  private final LineReader lineReader;
   private final Clock clock;
 
+  private LineReader lineReader;
+  private Terminal terminal;
+  private JCommander jcommanderForCompletions;
   private String prompt = null;
 
   @Parameter(
@@ -118,21 +119,22 @@ standard output and inserting a prefix ('out:' or 'err:') at the beginning of ev
           """)
   boolean encapsulateOutput = false;
 
-  ShellCommand(CommandRunner runner) throws IOException {
-    this(TerminalBuilder.terminal(), new SystemClock(), runner);
-    prompt = "nom > ";
-    lineReader.variable(LineReader.HISTORY_FILE, Path.of(USER_HOME.value(), HISTORY_FILE));
+  ShellCommand(CommandRunner runner) {
+    this.originalRunner = runner;
+    this.clock = new SystemClock();
+    this.prompt = "nom > ";
   }
 
   ShellCommand(Terminal terminal, Clock clock, CommandRunner runner) {
     this.originalRunner = runner;
+    this.terminal = terminal;
     this.lineReader = LineReaderBuilder.builder().terminal(terminal).build();
     this.clock = clock;
   }
 
   private void setPrompt(RegistryToolEnvironment environment, boolean alert) {
     // Do not set the prompt in tests.
-    if (lineReader.getTerminal() instanceof DumbTerminal) {
+    if (lineReader == null || lineReader.getTerminal() instanceof DumbTerminal) {
       return;
     }
     prompt =
@@ -143,7 +145,10 @@ private void setPrompt(RegistryToolEnvironment environment, boolean alert) {
   }
 
   public ShellCommand buildCompletions(JCommander jcommander) {
-    ((LineReaderImpl) lineReader).setCompleter(new JCommanderCompleter(jcommander));
+    this.jcommanderForCompletions = jcommander;
+    if (lineReader != null) {
+      ((LineReaderImpl) lineReader).setCompleter(new JCommanderCompleter(jcommander));
+    }
     return this;
   }
 
@@ -209,6 +214,19 @@ public void run(String[] args) {
   /** Run the shell until the user presses "Ctrl-D". */
   @Override
   public void run() {
+    if (lineReader == null) {
+      try {
+        this.terminal = TerminalBuilder.terminal();
+        this.lineReader = LineReaderBuilder.builder().terminal(terminal).build();
+        lineReader.variable(LineReader.HISTORY_FILE, Path.of(USER_HOME.value(), HISTORY_FILE));
+        if (jcommanderForCompletions != null) {
+          ((LineReaderImpl) lineReader)
+              .setCompleter(new JCommanderCompleter(jcommanderForCompletions));
+        }
+      } catch (IOException e) {
+        throw new RuntimeException("Failed to initialize terminal", e);
+      }
+    }
     // Wrap standard output and error if requested. We have to do so here in run because the flags
     // haven't been processed in the constructor.
     CommandRunner runner =