feat(cli): Add support for USB CDC to cli component, for use on ESP32-S2 for example

[finger563]

Description

• Update cli component to not error if compiled with support for USB-CDC
• Add espp::Cli::configure_stdin_stdout_usb_cdc method to configure stdin and stdout to use USB-CDC if available
• Add sdkconfig defaults file for using usb-cdc on ESP32-S2
• Add dependency to esp_vfs_console component, which is required for console output support on esp32-s2

Motivation and Context

• Ensures that cli component can be used with USB-CDC support enabled
• Allows using cli component on ESP32-S2

How has this been tested?

• Build and run cli/example on ESP32-S2 with USB-CDC enabled

Screenshots (if appropriate, e.g. schematic, board, console logs, lab pictures):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update
• Hardware (schematic, board, system design) change
• Software change

Checklist:

• My change requires a change to the documentation.
• I have added / updated the documentation related to this change via either README or WIKI

Software

• I have added tests to cover my changes.
• I have updated the .github/workflows/build.yml file to add my new test to the automated cloud build github action.
• All new and existing tests passed.
• My code follows the code style of this project.

[github-actions]

✅Static analysis result - no issues found! ✅

[Copilot]

Pull Request Overview

This PR adds USB CDC support to the cli component to enable its use on ESP32-S2 and other chips with native USB support.

Key Changes:

• Added configure_stdin_stdout_usb_cdc() method for USB CDC console configuration
• Removed the error directive that prevented compilation with CONFIG_ESP_CONSOLE_USB_CDC
• Added esp_vfs_console component dependency for USB CDC functionality

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
components/cli/src/cli.cpp	Initializes the static console_ member variable for storing file handles
components/cli/include/cli.hpp	Adds new USB CDC configuration method and removes incompatibility error
components/cli/example/sdkconfig.defaults.esp32s2	Configures ESP32-S2 example to use USB CDC console
components/cli/CMakeLists.txt	Adds required esp_vfs_console component dependency

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[Copilot]

[nitpick] Missing a final fflush/fsync sequence before setting configured_ = true. The configure_stdin_stdout_uart() (lines 146-147) and configure_stdin_stdout_usb_serial_jtag() (lines 180-181) functions both call fflush(stdout) and fsync(fileno(stdout)) at the end to ensure all output is written before completing configuration. Consider adding this for consistency:

fflush(stdout);
fsync(fileno(stdout));

configured_ = true;

Suggested change

	fflush(stdout);
	fsync(fileno(stdout));

[Copilot]

The VFS device should be registered before calling freopen on it. Currently, freopen is called on lines 204-206 before esp_vfs_dev_cdcacm_register() on line 208. This is inconsistent with the configure_stdin_stdout_vfs() function (lines 261 then 264-266) which registers the VFS first, then calls freopen. The order should be:

1. Register the VFS device with esp_vfs_dev_cdcacm_register()
2. Then call freopen to redirect stdin/stdout/stderr

Suggested change

	// redirect stdin, stdout, stderr to the USB CDC interface
	console_.in = freopen(dev_name.data(), "r", stdin);
	console_.out = freopen(dev_name.data(), "w", stdout);
	console_.err = freopen(dev_name.data(), "w", stderr);
	esp_vfs_dev_cdcacm_register();
	// Register the VFS device before redirecting streams
	esp_vfs_dev_cdcacm_register();
	// redirect stdin, stdout, stderr to the USB CDC interface
	console_.in = freopen(dev_name.data(), "r", stdin);
	console_.out = freopen(dev_name.data(), "w", stdout);
	console_.err = freopen(dev_name.data(), "w", stderr);

[Copilot]

The comment "Initialize VFS & UART" is misleading as this function configures USB CDC, not UART. It should say "Initialize VFS & USB CDC" to be accurate.

Suggested change

	// Initialize VFS & UART so we can use std::cout/cin
	// Initialize VFS & USB CDC so we can use std::cout/cin

[Copilot]

The setvbuf call should be placed before the VFS registration and freopen calls, similar to the pattern in configure_stdin_stdout_vfs() (line 258) and configure_stdin_stdout_uart() (line 121). The current placement after freopen may not properly configure stdin's buffering mode. Move this call to after the fflush/fsync operations (around line 199-200).

[Copilot]

The freopen calls can return NULL on failure, but these return values are not checked. While configure_stdin_stdout_vfs() also doesn't check these (lines 264-266), it would be good practice to verify that the operations succeeded before proceeding. Consider adding checks like:

if (!console_.in || !console_.out || !console_.err) {
  // Handle error
}

Suggested change

	console_.err = freopen(dev_name.data(), "w", stderr);
	console_.err = freopen(dev_name.data(), "w", stderr);
	// Check for errors in freopen calls
	if (!console_.in || !console_.out || !console_.err) {
	// Handle error: could not redirect stdio to USB CDC
	return;
	}