From de275540437c37d4f9ca905c74c58ee9a5dba925 Mon Sep 17 00:00:00 2001
From: Dion Moult <dion@thinkmoult.com>
Date: Thu, 7 Sep 2023 13:02:45 +1000
Subject: [PATCH] New substr formatting function.

---
 src/ifcopenshell-python/ifcopenshell/util/selector.py | 6 +++++-
 src/ifcopenshell-python/test/util/test_selector.py    | 2 ++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/ifcopenshell-python/ifcopenshell/util/selector.py b/src/ifcopenshell-python/ifcopenshell/util/selector.py
index 46fcd6c9e8..ea41323999 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/selector.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/selector.py
@@ -115,7 +115,7 @@ get_element_grammar = lark.Lark(
 format_grammar = lark.Lark(
     """start: function
 
-    function: round | format_length | lower | upper | title | concat | ESCAPED_STRING | NUMBER
+    function: round | format_length | lower | upper | title | concat | substr | ESCAPED_STRING | NUMBER
 
     round: "round(" function "," NUMBER ")"
     format_length: metric_length | imperial_length
@@ -125,6 +125,7 @@ format_grammar = lark.Lark(
     upper: "upper(" function ")"
     title: "title(" function ")"
     concat: "concat(" function ("," function)* ")"
+    substr: "substr(" function "," SIGNED_INT "," SIGNED_INT ")"
 
     // Embed common.lark for packaging
     DIGIT: "0".."9"
@@ -181,6 +182,9 @@ class FormatTransformer(lark.Transformer):
     def concat(self, args):
         return "".join(args)
 
+    def substr(self, args):
+        return str(args[0])[int(args[1]):int(args[2])]
+
     def round(self, args):
         return str(round(float(args[0]) / float(args[1])) * float(args[1]))
 
diff --git a/src/ifcopenshell-python/test/util/test_selector.py b/src/ifcopenshell-python/test/util/test_selector.py
index 4fd4972f75..d5306a84b3 100644
--- a/src/ifcopenshell-python/test/util/test_selector.py
+++ b/src/ifcopenshell-python/test/util/test_selector.py
@@ -34,6 +34,8 @@ class TestFormat():
         assert subject.format('title(\"fOo\")') == "Foo"
         assert subject.format('concat(\"fOo\", \"bar\")') == "fOobar"
         assert subject.format('upper(concat(\"fOo\", \"bar\"))') == "FOOBAR"
+        assert subject.format('substr(\"foobar\", 1, 2)') == "o"
+        assert subject.format('substr(\"foobar\", 1, -1)') == "ooba"
 
     def test_number_formatting(self):
         assert subject.format("round(123, 5)") == "125.0"