Lazily compile tree-sitter query

See comment on struct Lisp_TS_Query for why.  Previous commits adding
python and js support for tree-sitter breaks Emacs build if language
definitions aren't available at build time.  This commit fixes that.

Now query object don't compile the query upon creation, but stores the
query source and language symbol, and compiles upon first use (in
treesit-query-capture).

I want ts_ensure_query_compiled to return signal symbol and data
rather than signaling itself, because it's a helper function not lisp
function.  But because it calls ts_load_language, I had to update
ts_load_language to also use the signal symbol/data interface.

* src/treesit.h (struct Lisp_TS_Query): Add two new field.
* src/treesit.c (ts_load_language): Return signal symbol and data
rather than signaling itself.
(Ftreesit_langauge_available_p)
(Ftreesit_parser_create): Update usage of ts_load_language

(make_ts_query): Now returns a lisp object.
(ts_query_error_to_string): Moved because it's used by
ts_compose_query_signal_data.
(ts_compose_query_signal_data)
(ts_ensure_query_compiled): New functions.
(Ftreesit_query_compile): Delay compiling the query.
(Ftreesit_query_capture): Instead of creating a query object which
compiles the query, now goes two routes: if QUERY is a query object,
make sure it is compiled and use the TSQuery; if QUERY is a cons or
string, compile directly to TSQuery, and free it after use.  Creating
a lisp query requires the language symbol, but in this function we
only have TSLanguage.

1 files changed, 18 insertions, 2 deletions

diff --git a/src/treesit.h b/src/treesit.h
index 0c043f7d250..20e7cd4107c 100644
--- a/src/treesit.h
+++ b/src/treesit.h
@@ -84,11 +84,27 @@ struct Lisp_TS_Node
   ptrdiff_t timestamp;
 };
 
-/* A compiled tree-sitter query.  */
+/* A compiled tree-sitter query.
+
+   When we create a query object by treesit-compile-query, it is not
+   immediately compiled, because that would require the language
+   definition to be loaded.  For example, python.el contains
+
+   (defvar xxx (treesit-compile-query ...))
+
+   and (require 'python.el) requires python's language definition to
+   be available.  In the case of python.el, Emacs requires it when
+   building, so that breaks the build.  */
 struct Lisp_TS_Query
 {
   union vectorlike_header header;
-  /* Pointer to the query object.  */
+  /* Language symbol for the query.  */
+  Lisp_Object language;
+  /* Source lisp (sexp or string) query.  */
+  Lisp_Object source;
+  /* Pointer to the query object.  This can be NULL, meaning this
+     query is not initialized/compiled.  We compile the query when
+     it is used the first time (in treesit-query-capture).  */
   TSQuery *query;
   /* Pointer to a cursor.  If we are storing the query object, we
      might as well store a cursor, too.  */