TBSP

Tree-Based Source-Processing language

Language semantics

TBSP is a DSL which extends a backend language. It has a small syntax which was designed after Flex/Bison with the goal of reducing noise in programs using tree-sitter.

The only currently supported backend is C/C++.

<declaration-section>
%%
<rule-section>
%%
<code-section>

Example:

%language c
%%
enter translation_unit {
    puts("Hello World!");
}
%%
// @BAKE tbsp $@; gcc hello_world.tb.c $(pkg-config --libs tree-sitter tree-sitter-c); ./a.out
signed main(void) {
    tbtraverse("int i = 0;");
    return 0;
}

The above is a fully functional tbsp program. tbtraverse() will print "Hello World!" given any code.

NOTE: "@BAKE" is this tool here: https://github.com/emilwilliams/bake

Declaration section

%top { <...> }    // code to be pasted at the top of the source file
%language <lang>  // tree-sitter langauge name (for the right includes)

Rule section

The rule section is composed of any number of Rules.

Rules

[enter|leave]+ <node-type>+ { <...> }

• enter: signals that the rule applies when a node is pushed
• leave: signals that the rule applies when a node is popped leave and enter may be specified at the same time, the rule fill run on both pushes and pops.

<node-type> is the name of a tree-sitter node type. The rule will run only if such node is encountered. Multiple types can be specified which signals an OR relationship. Separate them with whitespace.

<...> is the code associated with the rule. Its provided in the backend language.

Queries

$$(-><selector>)*

Returns the named field of tbnode based on the selector or a null node if no such named field exists. Multiple selectors may be chained together. E.g. $$->mycstr->"declarator".

Code

The code section is verbatim pasted to the end of the output file.

Globals

/* Master function.
 * Rules are evaluated inside here.
 * Returns 0 on normal exit.
 */
int tbtraverse(const char * const code);

In tbtraverse

/* Rules are guaranteed to be inside tbtraverse(),
 *  this means that you may return from rules.
 */
return 0;

/* Rules are quarenteed to be inside a switch(),
 *  this means that break can be used to exit a
 *  rule early
 */
break;

/* Node corresponding to the rule being evaluated
 */
TSNode tbnode;

/* Macro that returns a `char *` to the tbnode's text value.
 * Not equivalent to ts_node_string().
 * Its the programmers responsibility to free() it.
 */
char * tbget_text;

/* Macro that returns a `char *` to the x's text value.
 * Not equivalent to ts_node_string().
 * Its the programmers responsibility to free() it.
 */
char * tbget_node_text(x);

/* Macro signalling whether we are executing as an enter rule.
 * Could be useful for shared rules.
 */
bool tbis_enter;