Combine included VCL modules into main and parse once

[ysugimoto]

Fixes #78

Resolve include modules that are declared at include "xxx"; statement, replace the parsed AST into its declaration position, and lint whole codes as a single VCL tree

This implementation still does not use DFS style parsing but it's should be lint properly.

Example

From #78, the example case of VCLs:

# dependency1.vcl
sub foo {
   set req.backend = httpbin_org;
}

# main.vcl

include "dependency1";

backend httpbin_org {
  .connect_timeout = 1s;
  .dynamic = true;
  .port = "443";
  .host = "httpbin.org";
  .first_byte_timeout = 20s;
  .max_connections = 500;
  .between_bytes_timeout = 20s;
  .share_key = "xei5lohleex3Joh5ie5uy7du";
  .ssl = true;
  .ssl_sni_hostname = "httpbin.org";
  .ssl_cert_hostname = "httpbin.org";
  .ssl_check_cert = always;
  .min_tls_version = "1.2";
  .max_tls_version = "1.2";
}

sub vcl_recv {
   call foo;
}

Then resolved VCL should be:

sub foo {
   set req.backend = httpbin_org;
}

backend httpbin_org {
  .connect_timeout = 1s;
  .dynamic = true;
  .port = "443";
  .host = "httpbin.org";
  .first_byte_timeout = 20s;
  .max_connections = 500;
  .between_bytes_timeout = 20s;
  .share_key = "xei5lohleex3Joh5ie5uy7du";
  .ssl = true;
  .ssl_sni_hostname = "httpbin.org";
  .ssl_cert_hostname = "httpbin.org";
  .ssl_check_cert = always;
  .min_tls_version = "1.2";
  .max_tls_version = "1.2";
}

sub vcl_recv {
   call foo;
}

And linter should not raise any errors.

Additional Specs

• Remote snippets (EdgeDictionary, ACL) also valid
• Nested inclusion also valid
• VCL error of included module still displays its filename and line

[ysugimoto]

Runner no longer needs to recognize the VCL is main or not, so RunMode could be simple as bit mode.

[ysugimoto]

Resolve include statement here.

[ysugimoto]

If statement may have a block statement so need to resolve recursively.

[davinci26]

what does block statement mean here? Can you give an example?

[davinci26]

(also we should probably move this to the code as a comment)

[ysugimoto]

The block statement may have include statement of embedding dynamic snippets inside (and probably include file is also valid).

For example:

sub vcl_fetch {
  if (req.restarts > 0) {
    include "snippet::<snippet_name>"; # Embed dynamic snippet here
  }
  ...
}

According to include statement, it is available in all subroutines so the above syntax should be valid and resolve inclusion recursively.

[ysugimoto]

Subroutine may have a block statement so need to resolve recursively.

[davinci26]

That is soooooo dope, super excited for this PR. will review tomorrow

[ysugimoto]

I'll resolve the conflict lately

[ysugimoto]

@davinci26 I've resolved conflict with main branch, PTAL?

[davinci26]

LGTM! Thanks for working on this

[davinci26]

when this + #99 is merged I will pull it in to our internal branch and test it on our VCL corpus as well and report back if I run into any issues