Add save command to the examples

[GraDKh]

Add save subcommand to example CLI for artifact export

TL;DR

Adds a new save subcommand to the examples CLI that allows exporting circuit artifacts to files.

What changed?

• Added a new save subcommand to the example CLI that can export:
  • Constraint system binary
  • Public witness values
  • Non-public data values
• Implemented a helper function write_serialized to handle serialization and file writing
• Updated the README with documentation for all CLI subcommands, including detailed usage examples for the new save command

How to test?

Run any example with the new save subcommand:

# Save only the constraint system
cargo run --release --example my_circuit -- save --cs-path out/cs.bin

# Save public values and non-public values
cargo run --release --example my_circuit -- save \
    --pub-witness-path out/public.bin \
    --non-pub-data-path out/non_public.bin

# Save all three artifacts
cargo run --release --example my_circuit -- save \
    --cs-path out/cs.bin \
    --pub-witness-path out/public.bin \
    --non-pub-data-path out/non_public.bin

Why make this change?

This change enables developers to export circuit artifacts for external analysis, debugging, or integration with other tools. The ability to save constraint systems and witness data separately provides flexibility for different workflows and testing scenarios.

[GraDKh]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Add verifier binary #876 : 2 dependent PRs (#906 , #907 )
• Add prover binary #875
• Add save command to the examples #874 👈 (View in Graphite)
• Add serializatoin support for the proof #873
• Add public witness serialization #872
• Add serialization support to the ContraintsSystem #871
• main

---

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[jadnohra]

@GraDKh Added 3 nits that would actually be nice, assuming you will address them and pre-approving

[graphite-app]

There appears to be a duplicate command argument flattening issue in the Save command struct. Both params and instance fields have the same type CommandArgs, which will cause clap to register the same argument names twice, resulting in runtime parsing conflicts.

Since both fields serve the same purpose (collecting command arguments), the params field on line 113 should be removed, leaving only the instance field on line 116. This will ensure arguments are properly parsed without conflicts when users run the save command.

/// Save constraint system, public witness, and non-public data to files if paths are provided
Save {
    /// Output path for the constraint system binary
    #[arg(long = "cs-path")]
    cs_path: Option<String>,

    /// Output path for the public witness binary
    #[arg(long = "pub-witness-path")]
    pub_witness_path: Option<String>,

    /// Output path for the non-public data (witness + internal) binary
    #[arg(long = "non-pub-data-path")]
    non_pub_data_path: Option<String>,

    // Remove this duplicate field
    // #[command(flatten)]
    // params: CommandArgs,

    #[command(flatten)]
    instance: CommandArgs,
}

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[GraDKh]

Addressed all the comments

[graphite-app]

The if let combined with && creates a syntax issue that could lead to unexpected behavior. The current structure:

if let Some(parent) = Path::new(path).parent()
    && !parent.as_os_str().is_empty()
{
    // ...
}

This attempts to use parent in the second condition, but the variable binding from if let doesn't properly extend through the && operator in this context.

Consider restructuring with either nested conditionals:

if let Some(parent) = Path::new(path).parent() {
    if !parent.as_os_str().is_empty() {
        // ...
    }
}

Or with proper parentheses to clarify the intent:

if let Some(parent) = Path::new(path).parent() && (!parent.as_os_str().is_empty()) {
    // ...
}

Suggested change

	if let Some(parent) = Path::new(path).parent()
	&& !parent.as_os_str().is_empty()
	{
	if let Some(parent) = Path::new(path).parent() {
	if !parent.as_os_str().is_empty()
	{

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[graphite-app]

Merge activity

• Sep 2, 7:12 AM UTC: GraDKh added this pull request to the Graphite merge queue.
• Sep 2, 7:13 AM UTC: CI is running for this pull request on a draft pull request (#908) due to your merge queue CI optimization settings.
• Sep 2, 7:20 AM UTC: Merged by the Graphite merge queue via draft PR: #908.