Fixed expanding runtime variables

[PunishedSnakePr]

For a detailed description please see commit message of first commit (826faf7).

[vstakhov]

Hum, do we have a test case for that? How have you reveled this issue?

[PunishedSnakePr]

I need to dig into the way you organize your test cases but sure I'll provide one.

In general, I was lacking a way to register variables at runtime (not at compile time) so users can declare their own variables and use them later on in the config. Therefore I used the "ucl_parser_set_variables_handler" to catch all dynamic/unknown variables, looked them up in a special "variable" config object and tried to replace the variable with its related content. Everything seemed to work as expected but in the end the variable was always empty.

Example config:

{
     vars {
        foo = hello
    }

    bar = ${vars.foo}
}

This is my original callback handler for the config example above:

static bool
__ucl_var_handler(const unsigned char *data,
                              size_t data_len,
                              unsigned char **replace,
                              size_t *replace_len,
                              bool *need_free,
                              void *priv_data)
{
    bool rv;
    char *path;
    struct ucl_parser *parser;
    ucl_object_t *root;
    const ucl_object_t *var;

    *need_free = false;

    path = strndup((const char*)data, data_len);
    if (!path)
        return false;

    parser = priv_data;
    rv = false;

    root = ucl_parser_get_object(parser);
    if (!root)
        goto err_path;

    var = ucl_object_lookup_path(root, path);
    if (!var)
        goto err_unref;

    *replace = (unsigned char*)var->value.sv;
    *replace_len = var->len;

    rv = true;

err_unref:
    ucl_object_unref(root);

err_path:
    free(path);

    return rv;
}

And this is the result when emitting "root" object:

{
     vars {
        foo = "hello";
    }

    bar = "";
}

My commit fixes this issue (as I'd expect it to work in general) and creates this output:

{
     vars {
        foo = "hello";
    }

    bar = "hello";
}

[PunishedSnakePr]

From my perspective this would be a cool feature anyway which helps reducing redundant config lines and increasing usability / flexibility. If you are fine with it, I am very happy to implement it as a native UCL feature.

[vstakhov]

I agree, you are right, thank you!