Fix infinite loop in Repl

[leculver]

Using ReadLine + IsNullOrEmpty + continue:

string line = Console.ReadLine();
if (string.IsNullOrEmpty(line))
    continue;

Produces an infinite loop if stdin was closed. For example, running under an llm and it closes the pipe to the tool.

[Copilot]

Pull request overview

Fixes an infinite loop in the REPL’s redirected-input mode by distinguishing EOF (Console.ReadLine() returning null) from an empty line (""). This addresses scenarios where the parent process closes stdin (e.g., when a driving process/LLM closes the pipe), causing ReadLine() to repeatedly return null.

Changes:

• Add an explicit line == null (EOF) check when input is redirected, and exit the input loop.
• Replace string.IsNullOrEmpty(line) with separate handling for EOF vs empty string.

Show a summary per file

File	Description
src/Microsoft.Diagnostics.Repl/ConsoleService.cs	Prevents an infinite loop on redirected stdin EOF by breaking out of the REPL read loop.

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• Files reviewed: 1/1 changed files
• Comments generated: 1