hrw4u: Fix u4wrh emitting quoted header names in HRW4U output

[Clendenin]

Summary

Header qualifiers that contain only characters legal in the HRW4U IDENT rule
were being wrapped in double quotes at emission time, which the grammar rejects
on re-parse. Quote a qualifier only when it actually contains characters that
require quoting.

Adds a parametrized unit test for Validator.unquote_if_ident covering
IDENT-safe stripping, space-containing qualifiers, empty strings, and
leading-digit rejection, symmetric with the existing needs_quotes and
quote_if_needed tests.

[Copilot]

Pull request overview

Fixes the u4wrh reverse compiler emitting double-quoted header names (e.g. "X-Foo") which the hrw4u grammar's IDENT rule rejects on re-parse. Introduces a Validator.unquote_if_ident helper that strips surrounding quotes when the inner value is a valid grammar IDENT, and applies it in the set/rm and add-header reverse-emit paths.

Changes:

• Add GRAMMAR_IDENT regex (mirrors hrw4u.g4 IDENT rule) and Validator.unquote_if_ident helper.
• Use the helper in _handle_set_rm_operation and the add-header branch of _handle_statement_function in hrw_symbols.py.
• Add reverse-compiler round-trip test fixtures and a parametrized unit test, plus an exceptions entry for the asymmetric hyphen_header case.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tools/hrw4u/src/common.py	Adds GRAMMAR_IDENT regex matching the grammar IDENT rule.
tools/hrw4u/src/validation.py	Adds Validator.unquote_if_ident helper.
tools/hrw4u/src/hrw_symbols.py	Strips quotes from IDENT-safe qualifiers in set/rm and add-header reverse emit.
tools/hrw4u/tests/test_errors.py	Parametrized unit test for unquote_if_ident.
tools/hrw4u/tests/data/vars/hyphen_header.input.txt	New round-trip fixture (hrw4u source).
tools/hrw4u/tests/data/vars/hyphen_header.output.txt	Expected HRW config output.
tools/hrw4u/tests/data/vars/exceptions.txt	Marks fixture as u4wrh-direction-only.

[zwoop]

While looking at this, these fixes actually unravel another weakness in the u4wrh code. Look at this example below, it'd be good to address this here, since the fixes in this PR opens up potentially really bad results in some odd cases:

leif@hel ~/apache/reviews/tools/hrw4u ±master⚡ » cat /tmp/foo.hrw
cond %{SEND_RESPONSE_HDR_HOOK}
    set-header "body" "v"
leif@hel ~/apache/reviews/tools/hrw4u ±master⚡ » uv run ./scripts/u4wrh /tmp/foo.hrw
SEND_RESPONSE {
    inbound.resp.body = "v";
}
leif@hel ~/apache/reviews/tools/hrw4u ±master⚡ » uv run ./scripts/u4wrh /tmp/foo.hrw | uv run ./scripts/hrw4u
cond %{SEND_RESPONSE_HDR_HOOK} [AND]
    set-body "v"

This is specific to the body header, but I think it'd be good to address this here, since the fixes makes it possible now to get into a really bad result.

[zwoop]

I think there's a second issue, with @-headers, and potentially other headers, e.g.

leif@hel ~/apache/reviews/tools/hrw4u ±master⚡ » cat /tmp/at.hrw
cond %{REMAP_PSEUDO_HOOK} [AND]
    set-header "@Foo" "v"
leif@hel ~/apache/reviews/tools/hrw4u ±master⚡ » uv run ./scripts/u4wrh /tmp/at.hrw
REMAP {
    inbound.req."@Foo" = "v";
}

That should produce:

REMAP {
    inbound.req.@Foo = "v";
}

[zwoop]

Here's a suggestion from Claude
hrw4u-qualifier-guard.patch

But, please take a closer look of course. Also, this still reserves

inbound.resp.body

for 'body' (i.e. can't have that as a header).

[zwoop]

See inline comments.