sarif-replay: quote source from artifact contents [PR117943]

sarif-replay: quote source from artifact contents [PR117943]

The diagnostic source-quoting machinery uses class file_cache
implemented in gcc/input.cc for (re)reading the source when
issuing diagnostics.

When sarif-replay issues a saved diagnostic it might be running
in a different path to where the .sarif file was captured, or
on an entirely different machine.

Previously such invocations would lead to the source-quoting
silently failing, even if the content of the file is recorded
in the .sarif file in the artifact "contents" property (which
gcc populates when emitting .sarif output).

This patch:
- adds the ability for slots in file_cache to be populated from memory
rather than from the filesystem
- exposes it in libgdiagnostics via a new entrypoint
- uses this in sarif-replay for any artifacts with a "contents"
property, so that source-quoting uses that rather than trying to read
from the path on the filesystem

gcc/ChangeLog:
	PR sarif-replay/117943
	* doc/libgdiagnostics/topics/physical-locations.rst
	(diagnostic_manager_new_file): Drop "const" from return type.
	* doc/libgdiagnostics/tutorial/02-physical-locations.rst: Drop
	"const" from "main_file" decl.
	* input.cc (file_cache::add_buffered_content): New.
	(file_cache_slot::set_content): New.
	(file_cache_slot::dump): Use m_file_path being null rather than
	m_fp to determine empty slots.  Dump m_fp.
	(find_end_of_line): Drop "const" from return type and param.  Add
	forward decl.
	(file_cache_slot::get_next_line): Fix "const"-ness.
	(selftest::test_reading_source_buffer): New.
	(selftest::input_cc_tests): Call it.
	* input.h (file_cache::add_buffered_content): New decl.
	* libgdiagnostics++.h (class file): Drop const-ness from m_inner.
	(file::set_buffered_content): New.
	* libgdiagnostics.cc (class content_buffer): New.
	(diagnostic_file::diagnostic_file): Add "mgr" param.
	(diagnostic_file::get_content): New.
	(diagnostic_file::set_buffered_content): New.
	(diagnostic_file::m_mgr): New.
	(diagnostic_file::m_content): New.
	(diagnostic_manager::new_file): Drop const-ness.  Pass *this to
	ctor.
	(diagnostic_file::set_buffered_content): New.
	(diagnostic_manager_new_file): Drop "const" from return type.
	(diagnostic_file_set_buffered_content): New entrypoint.
	(diagnostic_manager_debug_dump_file): Dump the content size,
	if any.
	* libgdiagnostics.h (diagnostic_manager_new_file): Drop "const"
	from return type.
	(diagnostic_file_set_buffered_content): New decl.
	* libgdiagnostics.map (diagnostic_file_set_buffered_content): New
	symbol.
	* libsarifreplay.cc (sarif_replayer::m_artifacts_arr): Convert
	from json::value to json::array.
	(sarif_replayer::handle_run_obj): Call handle_artifact_obj
	on all artifacts.
	(sarif_replayer::handle_artifact_obj): New.

gcc/testsuite/ChangeLog:
	PR sarif-replay/117943
	* sarif-replay.dg/2.1.0-valid/error-with-note.sarif: Update
	expected output to include quoted source code and underlines.
	* sarif-replay.dg/2.1.0-valid/signal-1.c.moved.sarif: New test.
	* sarif-replay.dg/2.1.0-valid/signal-1.c.sarif: Update expected
	output to include quoted source code and underlines.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>