Serialize output for variable width/offsets in Section and CrossSection

gdsfactory/cross_section.py

@@ -15,7 +15,8 @@
 from types import ModuleType
 from typing import TYPE_CHECKING, Any, Literal
 
-from pydantic import BaseModel, ConfigDict, Field
+import numpy as np
+from pydantic import BaseModel, ConfigDict, Field, field_serializer
 
 from gdsfactory.config import CONF, ErrorType
 
@@ -93,6 +94,13 @@ class Section(BaseModel):
 
     model_config = ConfigDict(extra="forbid", frozen=True)
 
+    @field_serializer("width_function", "offset_function")
+    def serialize_functions(self, func: Callable | None) -> str | None:
+        if func is None:
+            return None
+        t_values = np.linspace(0, 1, 11)
+        return ",".join([str(round(width, 3)) for width in func(t_values)])
+
 
 class ComponentAlongPath(BaseModel):
     """A ComponentAlongPath object to place along an extruded path.
@@ -386,6 +394,15 @@ class Transition(CrossSection):
     cross_section2: CrossSectionSpec
     width_type: WidthTypes | Callable = "sine"
 
+    @field_serializer("width_type")
+    def serialize_width(self, width_type: WidthTypes | Callable) -> str | None:
+        if isinstance(width_type, str):
+            return width_type
+        t_values = np.linspace(0, 1, 10)
+        return ",".join(
+            [str(round(width, 3)) for width in width_type(t_values, *self.width)]
+        )
+
     @property
     def width(self) -> tuple[float, float]:
         return (

gdsfactory/path.py

@@ -617,7 +617,7 @@ def dWdx(w, x, neff_w, wavelength, alpha):
 def transition(
     cross_section1: CrossSectionSpec,
     cross_section2: CrossSectionSpec,
-    width_type: WidthTypes = "sine",
+    width_type: WidthTypes | Callable = "sine",
 ) -> Transition:
     """Returns a smoothly-transitioning between two CrossSections.
 

tests/test_cross_section.py

@@ -147,6 +147,35 @@ def test_extrude_transition_component():
     assert c["o2"].width == w2
 
 
+def test_cross_section_variable_width_section():
+    """Make sure serialization for Section with variable width is different for different width functions.
+    This will fail if @gf.cell is reusing the first Component."""
+    import numpy as np
+
+    def get_custom_width_func(n: int = 1):
+        def _width_func(t):
+            return 3 + np.cos(2 * np.pi * t * n)
+
+        return _width_func
+
+    P = gf.path.straight(length=40, npoints=100)
+
+    s1 = gf.Section(
+        width=0, width_function=get_custom_width_func(n=1), offset=0, layer=(1, 0)
+    )
+    s2 = gf.Section(
+        width=0, width_function=get_custom_width_func(n=5), offset=0, layer=(1, 0)
+    )
+
+    X1 = gf.CrossSection(sections=(s1,))
+    X2 = gf.CrossSection(sections=(s2,))
+
+    p1 = gf.path.extrude(P, cross_section=X1)
+    p2 = gf.path.extrude(P, cross_section=X2)
+
+    assert p1 is not p2
+
+
 if __name__ == "__main__":
     # test_transition_names()
     # test_copy()

tests/test_paths_transition4.py

@@ -0,0 +1,56 @@
+from __future__ import annotations
+
+import numpy as np
+
+import gdsfactory as gf
+
+
+def get_custom_width_func(n: int = 5):
+    def _width_func(t, y1, y2):
+        return (y2 - y1) + np.cos(2 * np.pi * t * n)
+
+    return _width_func
+
+
+def test_transition_type_callable_multiple() -> None:
+    """Ensure that the width_type serialization works properly"""
+    width1 = 1.0
+    width2 = 2.0
+    x1 = gf.cross_section.strip(width=width1)
+    x2 = gf.cross_section.strip(width=width2)
+
+    p = gf.path.straight(length=10, npoints=100)
+
+    xt1 = gf.path.transition(
+        cross_section1=x1, cross_section2=x2, width_type=get_custom_width_func(n=1)
+    )
+    xt2 = gf.path.transition(
+        cross_section1=x1, cross_section2=x2, width_type=get_custom_width_func(n=5)
+    )
+    s1 = p.extrude(cross_section=xt1)
+    s2 = p.extrude(cross_section=xt2)
+    assert s1 is not s2
+
+
+if __name__ == "__main__":
+    test_transition_type_callable_multiple()
+
+    width1 = 1.0
+    width2 = 2.0
+    x1 = gf.cross_section.strip(width=width1)
+    x2 = gf.cross_section.strip(width=width2)
+
+    p = gf.path.straight(length=10, npoints=100)
+
+    xt1 = gf.path.transition(
+        cross_section1=x1, cross_section2=x2, width_type=get_custom_width_func(n=1)
+    )
+    xt2 = gf.path.transition(
+        cross_section1=x1, cross_section2=x2, width_type=get_custom_width_func(n=5)
+    )
+    c = gf.Component()
+    s1 = c << p.extrude(cross_section=xt1)
+    s2 = c << p.extrude(cross_section=xt2)
+    s2.movey(-10)
+
+    c.show()