Re: [PATCH] tests: add test for json-streamer.c error recovery

[Markus Armbruster <armbru@redhat.com>]

One more thing...

Paolo Bonzini <pbonzini@redhat.com> writes:

> Before rewriting the error recovery code to work in a push parsing
> setup, make sure that we have tests for it.
>
> Cover various cases of invalid JSON, to check that structural
> recovery based on balanced brackets and braces works; and
> lexer-based recovery which documents "\f" as a sure fire
> way to reset the lexer.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  tests/unit/check-json-parser.c | 145 +++++++++++++++++++++++++++++++++
>  tests/unit/meson.build         |   1 +
>  2 files changed, 146 insertions(+)
>  create mode 100644 tests/unit/check-json-parser.c
>
> diff --git a/tests/unit/check-json-parser.c b/tests/unit/check-json-parser.c
> new file mode 100644
> index 00000000000..ca2d5f41097
> --- /dev/null
> +++ b/tests/unit/check-json-parser.c
> @@ -0,0 +1,145 @@
> +/*
> + * Unit tests for JSON Parser error recovery
> + *
> + * Copyright 2026 Red Hat
> + * Author: Paolo Bonzini <pbonzini@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
> + * See the COPYING.LIB file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +
> +#include "qapi/error.h"
> +#include "qobject/qbool.h"
> +#include "qobject/json-parser.h"
> +
> +typedef struct ParseResult {
> +    int errors;
> +    QObject *result;
> +} ParseResult;
> +
> +static void parse_emit(void *opaque, QObject *json, Error *err)
> +{
> +    ParseResult *r = opaque;
> +
> +    if (err) {
> +        r->errors++;
> +        error_free(err);
> +    } else {
> +        qobject_unref(r->result);

Unexpected calls to parse_emit() won't be detected as long as the last
one yields the expected expression.  Worth detecting?  I'm not quite
sure.  As far as I can tell, this is not reached at the moment.

The stupidest way to detect is to assert r->result is still null.

Can't do that if we want to cover parsing multiple JSON expressions in
sequence.  Collect all the results in an array?

Leave for later, with a short comment?

Up to you.

> +        r->result = json;
> +    }
> +}

[...]