What causes "JSON output isn't implemented yet" in GitoxideLabs/gitoxide?

Run with human output and parse the text report

JSON output isn't implemented yet

Error message

JSON output isn't implemented yet

What it means

Guard clause at the top of `attributes::validate_baseline`, the plumbing command that validates gitattributes against a baseline. Like most gitoxide-core plumbing commands, only human-readable output is implemented; if the caller selects any other OutputFormat (e.g. JSON) the function bails immediately before doing any work. It fires purely from user format selection and indicates a missing feature, not a data problem — no JSON serializer exists for attribute validation results.

Solutions

Run with human output and parse the text report
Capture the mismatch listing written to stderr and format it yourself
File/track an upstream feature request for JSON baseline validation output

Example fix

// before
validate_baseline(repo, repo_path, out, err, Options { format: OutputFormat::Json, .. })?;
// after
validate_baseline(repo, repo_path, out, err, Options { format: OutputFormat::Human, .. })?;

Defensive patterns

Strategy: validation

Validate before calling

if format != OutputFormat::Human {
    eprintln!("validate-baseline: JSON not implemented; using Human");
    format = OutputFormat::Human;
}

Try / catch

match validate_baseline(repo, repo_path, out, err, opts) {
    Err(e) if e.to_string().contains("JSON output isn't implemented") => {
        // rerun with Human format
    }
    other => other?,
}

Prevention

Request Human output for baseline validation
Post-process stderr text reports if structured data is needed
Track upstream JSON support before wiring CI to it

When it happens

Trigger: Calling `repository::attributes::validate_baseline` with `format == OutputFormat::Json` (or any non-Human variant) via the corresponding CLI flag.

Common situations: CI pipelines requesting JSON reports from baseline validation; tooling that assumes all subcommands emit JSON.

Related errors

AI-assisted analysis of GitoxideLabs/gitoxide@e73179060b (2026-09-08). Data as JSON: /api/errors/fcfb8931d584f126. Report an issue: GitHub.

Appendix: source

Thrown at gitoxide-core/src/repository/attributes/validate_baseline.rs:45

    use crate::{
        OutputFormat,
        repository::attributes::{query::attributes_cache, validate_baseline::Options},
    };

    pub fn validate_baseline(
        repo: gix::Repository,
        paths: Option<impl Iterator<Item = BString> + Send + 'static>,
        mut progress: impl gix::NestedProgress + 'static,
        mut out: impl io::Write,
        mut err: impl io::Write,
        Options {
            format,
            statistics,
            mut ignore,
        }: Options,
    ) -> anyhow::Result<()> {
        if format != OutputFormat::Human {
            bail!("JSON output isn't implemented yet");
        }

        if repo.is_bare() {
            writeln!(
                err,
                "Repo at '{repo}' is bare - disabling git-ignore baseline as `git check-ignore` needs a worktree",
                repo = repo.path().display()
            )
            .ok();
            ignore = false;
        }
        let mut num_entries = None;
        let paths = paths.map_or_else(
            {
                let repo = repo.clone();
                let num_entries = &mut num_entries;
                move || -> anyhow::Result<_> {
                    let index = repo.index_or_load_from_head()?.into_owned();

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