diagnostics: rework experimental-html output [PR116792]

diagnostics: rework experimental-html output [PR116792]

This patch reworks the HTML output from the the option
  -fdiagnostics-add-output=experimental-html
so that for source quoting and path printing, rather than simply adding
the textual output inside <pre> elements, it breaks up the output
into HTML tags reflecting the structure of the output, using CSS, SVG
and a little javascript to help the user navigate the diagnostics and
the events within any paths.

This uses ideas from the patch I posted in:
  https://gcc.gnu.org/pipermail/gcc-patches/2020-November/558603.html
but reworks the above patch so that:
* rather than printing source to a pretty_printer, the HTML is created
  by building a DOM tree in memory, using a new xml::printer class.  This
  should be less error-prone than the pretty_printer approach, since it
  ought to solve escaping issues.  Instead of a text vs html boolean,
  the code is generalized via templates with to_text vs to_html sinks.
  This templatization applies both to path-printing and
  diagnostic-show-locus.cc.
* the HTML output can have multiple diagnostics and multiple paths rather
  than just a single path.  The javascript keyboard controls now cycle
  through all diagnostics and all events within them

An example of the output can be seen at:
  https://dmalcolm.fedorapeople.org/gcc/2025-05-27/malloc-1.c.html
where the keys "j" and "k" cycle through diagnostics and events
within them.

gcc/ChangeLog:
	PR other/116792
	* diagnostic-format-html.cc: Define INCLUDE_STRING.
	Include "xml.h", "xml-printer.h", and "json.h".
	(html_generation_options::html_generation_options): New.
	(namespace xml): Move decls to xml.h and convert from using
	label_text to std::string.
	(xml::text::write_as_xml): Reimplement indentation so it is done
	by this node, rather than the parent.
	(xml::node_with_children::add_text): Convert from label_text to
	std::string.  Consolidate runs of text into a single node.
	(xml::document::write_as_xml): Reimplement indentation.
	(xml::element::write_as_xml): Reimplement indentation so it is
	done by this node, rather than the parent.  Convert from
	label_text to std::string.  Update attribute-printing to new
	representation to preserve insertion order.
	(xml::element::set_attr): Convert from label_text to std::string.
	Record insertion order.
	(xml::raw::write_as_xml): New.
	(xml::printer::printer): New.
	(xml::printer::push_tag): New.
	(xml::printer::push_tag_with_class): New.
	(xml::printer::pop_tag): New.
	(xml::printer::set_attr): New.
	(xml::printer::add_text): New.
	(xml::printer::add_raw): New.
	(xml::printer::push_element): New.
	(xml::printer::append): New.
	(xml::printer::get_insertion_point): New.
	(html_builder::add_focus_id): New.
	(html_builder::m_html_gen_opts): New field.
	(html_builder::m_head_element): New field.
	(html_builder::m_next_diag_id): New field.
	(html_builder::m_ui_focus_ids): New field.
	(make_div): Convert from label_text to std::string.
	(make_span): Likewise.
	(HTML_STYLE): New.
	(HTML_SCRIPT): New.
	(html_builder::html_builder): Fix indentation.  Add
	"html_gen_opts" param.  Initialize new fields.  Reimplement
	using xml::printer.  Optionally add style and script tags.
	(class html_path_label_writer): New.
	(html_builder::make_element_for_diagnostic): Convert from
	label_text to std::string. Set "id" on "gcc-diagnostic" and
	"gcc-message" <div> elements; add the latter to the focus ids.
	Use diagnostic_context::maybe_show_locus_as_html rather than
	html_builder::make_element_for_source.  Use print_path_as_html
	rather than html_builder::make_element_for_path.
	(html_builder::make_element_for_source): Drop.
	(html_builder::make_element_for_path): Drop.
	(html_builder::make_element_for_patch): Convert from label_text to
	std::string.
	(html_builder::make_metadata_element): Likewise.  Use
	xml::printer.
	(html_builder::make_element_for_metadata): Convert from label_text
	to std::string.
	(html_builder::emit_diagram): Expand comment.
	(html_builder::flush_to_file): Write out initializer for
	"focus_ids" into javascript.
	(html_output_format::html_output_format): Add param
	"html_gen_opts" and use it to initialize m_builder.
	(html_file_output_format::html_file_output_format): Likewise, to
	initialize base class.
	(make_html_sink): Likewise, to pass to ctor.
	(selftest::test_html_diagnostic_context::test_html_diagnostic_context):
	Set up html_generation_options.
	(selftest::html_buffered_output_format::html_buffered_output_format):
	Add html_gen_opts param.
	(selftest::test_simple_log): Add id attributes to expected text
	for "gcc-diagnostic" and "gcc-message" elements.  Update
	whitespace for indentation fixes.
	(selftest::test_metadata): Update whitespace for indentation
	fixes.
	(selftest::test_printer): New selftest.
	(selftest::test_attribute_ordering): New selftest.
	(selftest::diagnostic_format_html_cc_tests): Call the new
	selftests.
	* diagnostic-format-html.h (struct html_generation_options): New.
	(make_html_sink): Add "html_gen_opts" param.
	(print_path_as_html): New decl.
	* diagnostic-path-output.cc: Define INCLUDE_MAP.  Add includes of
	"diagnostic-format-html.h", "xml.h", and "xml-printer.h".
	(path_print_policy::path_print_policy): Add ctor.
	(path_print_policy::get_diagram_theme): Fix whitespace.
	(struct stack_frame): New.
	(begin_html_stack_frame): New function.
	(end_html_stack_frame): New function.
	(emit_svg_arrow): New function.
	(event_range::print): Rename to...
	(event_range::print_as_text): ...this.  Update call to
	diagnostic_start_span.
	(event_range::print_as_html): New, based on the above, but ported
	from pretty_printer to xml::printer.
	(thread_event_printer::print_swimlane_for_event_range): Rename
	to...
	(thread_event_printer::print_swimlane_for_event_range_as_text):
	...this.  Update for renaming of event_range::print to
	event_range::print_as_text.
	(thread_event_printer::print_swimlane_for_event_range_as_html):
	New.
	(print_path_summary_as_text): Update for "_as_text" renaming.
	(print_path_summary_as_html): New.
	(print_path_as_html): New.
	* diagnostic-show-locus.cc: Add defines of INCLUDE_MAP and
	INCLUDE_STRING.  Add includes of "xml.h" and "xml-printer.h".
	(struct char_display_policy): Replace "m_print_cb" with
	"m_print_text_cb" and "m_print_html_cb".
	(struct to_text): New.
	(struct to_html): New.
	(get_printer): New.
	(default_diagnostic_start_span_fn<to_text>): New.
	(default_diagnostic_start_span_fn<to_html>): New.
	(class layout): Update "friend class layout_printer;" for
	template.
	(enum class margin_kind): New.
	(class layout_printer): Convert into a template.
	(layout_printer::m_pp): Replace field with...
	(layout_printer::m_sink): ...this.
	(layout_printer::m_colorizer): Drop field in favor of a pointer
	in the "to_text" sink.
	(default_print_decoded_ch): Convert into a template.
	(escape_as_bytes_print): Likewise.
	(escape_as_unicode_print): Likewise.
	(make_char_policy): Update to use both text and html callbacks.
	(layout_printer::print_gap_in_line_numbering): Replace with...
	(layout_printer<to_text>::print_gap_in_line_numbering): ...this
	(layout_printer<to_html>::print_gap_in_line_numbering): ...and
	this.
	(layout_printer::print_source_line): Convert to template, using
	m_sink.
	(layout_printer::print_leftmost_column): Likewise.
	(layout_printer::start_annotation_line): Likewise.
	(layout_printer<to_text>::end_line): New.
	(layout_printer<to_html>::end_line): New.
	(layout_printer::print_annotation_line): Convert to template,
	using m_sink.
	(class line_label): Add field m_original_range_idx.
	(layout_printer<to_text>::begin_label): New.
	(layout_printer<to_html>::begin_label): New.
	(layout_printer<to_text>::end_label): New.
	(layout_printer<to_html>::end_label): New.
	(layout_printer::print_any_labels): Convert to template, using
	m_sink.
	(layout_printer::print_leading_fixits): Likewise.
	(layout_printer::print_trailing_fixits): Likewise.
	(layout_printer::print_newline): Drop.
	(layout_printer::move_to_column): Convert to template, using
	m_sink.
	(layout_printer::show_ruler): Likewise.
	(layout_printer::print_line): Likewise.
	(layout_printer::print_any_right_to_left_edge_lines): Likewise.
	(layout_printer::layout_printer): Likewise.
	(diagnostic_context::maybe_show_locus_as_html): New.
	(diagnostic_source_print_policy::diagnostic_source_print_policy):
	Update for split of start_span_cb into text vs html variants.
	(diagnostic_source_print_policy::print): Update for use of
	templates; use to_text.
	(diagnostic_source_print_policy::print_as_html): New.
	(layout_printer::print): Convert to template, using m_sink.
	(selftest::make_element_for_locus): New.
	(selftest::make_raw_html_for_locus): New.
	(selftest::test_layout_x_offset_display_utf8): Update for use of
	templates.
	(selftest::test_layout_x_offset_display_tab): Likewise.
	(selftest::test_one_liner_caret_and_range): Add test coverage of
	HTML output.
	(selftest::test_one_liner_labels): Likewise.
	* diagnostic.cc (diagnostic_context::initialize): Update for split
	of start_span_cb into text vs html variants.
	(default_diagnostic_start_span_fn): Move to
	diagnostic-show-locus.cc, converting to template.
	* diagnostic.h (class xml::printer): New forward decl.
	(diagnostic_start_span_fn): Replace typedef with "using",
	converting to a template.
	(struct to_text): New forward decl.
	(struct to_html): New forward decl.
	(get_printer): New decl.
	(diagnostic_location_print_policy::print_text_span_start): New
	decl.
	(diagnostic_location_print_policy::print_html_span_start): New
	decl.
	(class html_label_writer): New.
	(diagnostic_source_print_policy::print_as_html): New decl.
	(diagnostic_source_print_policy::get_start_span_fn): Replace
	with...
	(diagnostic_source_print_policy::get_text_start_span_fn): ...this
	(diagnostic_source_print_policy::get_html_start_span_fn): ...and
	this
	(diagnostic_source_print_policy::m_start_span_cb): Replace with...
	(diagnostic_source_print_policy::m_text_start_span_cb): ...this
	(diagnostic_source_print_policy::m_html_start_span_cb): ...and
	this.
	(diagnostic_context::maybe_show_locus_as_html): New decl.
	(diagnostic_context::m_text_callbacks::m_start_span): Replace
	with...
	(diagnostic_context::m_text_callbacks::m_text_start_span): ...this
	(diagnostic_context::m_text_callbacks::m_html_start_span): ...and
	this.
	(diagnostic_start_span): Update for template change.
	(diagnostic_show_locus_as_html): New inline function.
	(default_diagnostic_start_span_fn): Convert to template.
	* doc/invoke.texi (experimental-html): Add "css" and "javascript"
	keys.
	* opts-diagnostic.cc (html_scheme_handler::make_sink): Likewise.
	* selftest-diagnostic.cc
	(selftest::test_diagnostic_context::start_span_cb): Update for
	template changes.
	* selftest-diagnostic.h
	(selftest::test_diagnostic_context::start_span_cb): Likewise.
	* xml-printer.h: New file.
	* xml.h: New file, based on material in diagnostic-format-html.cc,
	but using std::string rather than label_text.
	(xml::element::m_key_insertion_order): New field.
	(struct xml::raw): New.

gcc/fortran/ChangeLog
	PR other/116792
	* error.cc (gfc_diagnostic_start_span): Update for diagnostic.h
	changes.

gcc/testsuite/ChangeLog:
	PR other/116792
	* gcc.dg/html-output/missing-semicolon.c: Add ":javascript=no" to
	html output.
	* gcc.dg/html-output/missing-semicolon.py: Move repeated
	definitions into lib/htmltest.py.
	* gcc.dg/plugin/diagnostic_group_plugin.cc: Update for template
	changes.
	* gcc.dg/plugin/diagnostic-test-metadata-html.c: Add
	":javascript=no" to html output.  Add
	"-fdiagnostics-show-line-numbers".
	* gcc.dg/plugin/diagnostic-test-metadata-html.py: Move repeated
	definitions into lib/htmltest.py.  Add checks of annotated source.
	* gcc.dg/plugin/diagnostic-test-paths-2.c: Add ":javascript=no" to
	html output.
	* gcc.dg/plugin/diagnostic-test-paths-2.py: Move repeated
	definitions into lib/htmltest.py.  Add checks of execution path.
	* gcc.dg/plugin/diagnostic-test-paths-4.c: Add
	-fdiagnostics-add-output=experimental-html:javascript=no.  Add
	invocation ot diagnostic-test-paths-4.py.
	* gcc.dg/plugin/diagnostic-test-paths-4.py: New test script.
	* gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers.c: Add
	-fdiagnostics-add-output=experimental-html:javascript=no.  Add
	invocation of diagnostic-test-show-locus.py.
	* gcc.dg/plugin/diagnostic-test-show-locus.py: New test script.
	* lib/htmltest.py: New test support script.

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