Remove unconditional scope pass-throughs for empty elements

Elements that could be empty (i.e., not have subnodes) connected
their before and after scopes unconditionally. This could lead to
exponential blow ups when they were not empty: the direct pass
through and the path through the elements were equivalent.

Guarding the pass-through with a conditional that ensures it is
only created when there are indeed no sub nodes prevents this.

languages/tree-sitter-stack-graphs-javascript/src/stack-graphs.tsg

@@ -554,10 +554,10 @@ inherit .return_or_yield
   node @export_clause.source
 }
 
-; LATER-TODO tree sitter doesn't yet support empty switch bodies
-; THIS IS A HUGE HACK AND MUST BE FIXED
-(export_clause)@export_clause {
-  edge @export_clause.after_scope -> @export_clause.before_scope
+(export_clause (_)* @clauses)@export_clause {
+  if (is-empty @clauses) {
+    edge @export_clause.after_scope -> @export_clause.before_scope
+  }
 }
 
 (export_clause
@@ -853,9 +853,7 @@ inherit .return_or_yield
 
 ; import "foo.js";
 ; only used for side effects not imports.
-; HACK this is not a good solution, but we can't do better with the
-; current tree sitter grammar
-(import_statement)@import_stmt {
+(import_statement . source:(_))@import_stmt {
   edge @import_stmt.after_scope -> @import_stmt.before_scope
 }
 
@@ -926,10 +924,10 @@ inherit .return_or_yield
   node @named_imports.source
 }
 
-; LATER-TODO tree sitter doesn't yet support empty named imports
-; THIS IS A HUGE HACK AND MUST BE FIXED
-(named_imports)@named_imports {
-  edge @named_imports.after_scope -> @named_imports.before_scope
+(named_imports (_)* @specs)@named_imports {
+  if (is-empty @specs) {
+    edge @named_imports.after_scope -> @named_imports.before_scope
+  }
 }
 
 (named_imports
@@ -1421,12 +1419,15 @@ inherit .return_or_yield
 }
 
 
-; LATER-TODO tree sitter doesn't yet support empty switch bodies
-; THIS IS A HUGE HACK AND MUST BE FIXED
 (class_body)@class_body {
   node @class_body.after_scope
   node @class_body.before_scope
-  edge @class_body.after_scope -> @class_body.before_scope
+}
+
+(class_body (_)* @decls)@class_body {
+  if (is-empty @decls) {
+    edge @class_body.after_scope -> @class_body.before_scope
+  }
 }
 
 (class_body
@@ -1694,8 +1695,6 @@ inherit .return_or_yield
     edge @switch_stmt.after_scope -> @body.after_scope
 }
 
-; LATER-TODO tree sitter doesn't yet support empty switch bodies
-; THIS IS A HUGE HACK AND MUST BE FIXED
 (switch_body)@switch_body {
   node @switch_body.after_scope
   node @switch_body.before_scope
@@ -1743,10 +1742,10 @@ inherit .return_or_yield
   node @switch_case.before_scope
 }
 
-; LATER-TODO tree sitter doesnt yet support switch case's with no statements
-; THIS IS A HUGE HACK AND MUST BE FIXED
-(switch_case)@switch_case {
+(switch_case (_)* @stmts)@switch_case {
+  if (is-empty @stmts) {
     edge @switch_case.after_scope -> @switch_case.before_scope
+  }
 }
 
 ; switch case, non-empty statements, first statement
@@ -1786,10 +1785,10 @@ inherit .return_or_yield
   node @switch_default.before_scope
 }
 
-; LATER-TODO tree sitter doesnt yet support empty defaults
-; THIS IS A HUGE HACK AND MUST BE FIXED
-(switch_default)@switch_default {
-  edge @switch_default.after_scope -> @switch_default.before_scope
+(switch_default (_)* @defaults)@switch_default {
+  if (is-empty @defaults) {
+    edge @switch_default.after_scope -> @switch_default.before_scope
+  }
 }
 
 ; switch default, non-empty statements, first statement
@@ -2237,10 +2236,10 @@ inherit .return_or_yield
 ;; #### Template Strings
 
 ; template_strings w/ no substitutions
-; LATER-TODO tree sitter queries don't let us find the absence of substitutions
-; THIS IS A HUGE HACK AND MUST BE FIXED
-(template_string)@template_string {
-  edge @template_string.after_scope -> @template_string.before_scope
+(template_string (_)* @substs)@template_string {
+  if (is-empty @substs) {
+    edge @template_string.after_scope -> @template_string.before_scope
+  }
 }
 
 ; nonempty template string, value
@@ -2390,10 +2389,10 @@ inherit .return_or_yield
 }
 
 ; empty objects
-; LATER-TODO currently unsupported by tree sitter queries
-; THIS IS A HUGE HACK AND MUST BE FIXED
-(object)@object_expr {
-  edge @object_expr.after_scope -> @object_expr.before_scope
+(object (_)* @entries)@object_expr {
+  if (is-empty @entries) {
+    edge @object_expr.after_scope -> @object_expr.before_scope
+  }
 }
 
 ; non-empty objects, scopes, first entry
@@ -2541,10 +2540,10 @@ inherit .return_or_yield
 }
 
 ; empty arrays
-; LATER-TODO currently unsupported by tree sitter queries
-; THIS IS A HUGE HACK AND MUST BE FIXED
-(array)@array_expr {
-  edge @array_expr.after_scope -> @array_expr.before_scope
+(array (_)* @elems)@array_expr {
+  if (is-empty @elems) {
+    edge @array_expr.after_scope -> @array_expr.before_scope
+  }
 }
 
 ; nonempty arrays, first element
@@ -2587,14 +2586,15 @@ inherit .return_or_yield
 
 ;; #### Formal Parameters
 
-; LATER-TODO scope propagation through empty formal parameters
-; currently unsupported by tree sitter queries
-; THIS IS A HUGE HACK AND MUST BE FIXED
-
 (formal_parameters)@formal_params {
   node @formal_params.after_scope
   node @formal_params.before_scope
-  edge @formal_params.after_scope -> @formal_params.before_scope
+}
+
+(formal_parameters (_)* @params)@formal_params {
+  if (is-empty @params) {
+    edge @formal_params.after_scope -> @formal_params.before_scope
+  }
 }
 
 ; first parameter
@@ -2985,12 +2985,15 @@ inherit .return_or_yield
 
 ;; #### Arguments
 
-; LATER-TODO currently unsupported by tree sitter queries
-; THIS IS A HUGE HACK AND MUST BE FIXED
 (arguments)@arguments {
   node @arguments.after_scope
   node @arguments.before_scope
-  edge @arguments.after_scope -> @arguments.before_scope
+}
+
+(arguments (_)* @args)@arguments {
+  if (is-empty @args) {
+    edge @arguments.after_scope -> @arguments.before_scope
+  }
 }
 
 (arguments
@@ -3701,8 +3704,10 @@ inherit .return_or_yield
 ; LATER-TODO scope propagation through empty object patterns
 ; currently unsupported by tree sitter queries
 ; THIS IS A HUGE HACK AND MUST BE FIXED
-(object_pattern)@object_pat {
-  edge @object_pat.after_scope -> @object_pat.before_scope
+(object_pattern (_)* @entries)@object_pat {
+  if (is-empty @entries) {
+    edge @object_pat.after_scope -> @object_pat.before_scope
+  }
 }
 
 ; scope propagation through object patterns, first entry
@@ -3823,11 +3828,10 @@ inherit .return_or_yield
 
 ;; #### Array Patterns
 
-; LATER-TODO scope propagation through empty array patterns
-; currently unsupported by tree sitter queries
-; THIS IS A HUGE HACK AND MUST BE FIXED
-(array_pattern)@array_pat {
-  edge @array_pat.after_scope -> @array_pat.before_scope
+(array_pattern (_)* @pats)@array_pat {
+  if (is-empty @pats) {
+    edge @array_pat.after_scope -> @array_pat.before_scope
+  }
 }
 
 ; scope propagation through array patterns, first element