From d22399dbf5ab90b7b88ec478b2981c4c2771488e Mon Sep 17 00:00:00 2001
From: Niko Savola <nikosavola@google.com>
Date: Mon, 27 Nov 2023 15:07:39 -0800
Subject: [PATCH] Add pins in `taper_cross_section`, closes #2329

---
 gdsfactory/add_tapers_cross_section.py       | 26 +++++++++++++++-----
 gdsfactory/components/taper_cross_section.py | 15 ++++++++++-
 gdsfactory/cross_section.py                  |  7 ++++--
 3 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/gdsfactory/add_tapers_cross_section.py b/gdsfactory/add_tapers_cross_section.py
index 6853170f17..e5ac8d7649 100644
--- a/gdsfactory/add_tapers_cross_section.py
+++ b/gdsfactory/add_tapers_cross_section.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from collections.abc import Callable
+from functools import partial
 
 import gdsfactory as gf
 from gdsfactory.cell import cell
@@ -13,7 +14,7 @@
 
 @cell
 def add_tapers(
-    component: Component,
+    component: ComponentSpec,
     taper: ComponentSpec = taper_cross_section,
     select_ports: Callable | None = select_ports_optical,
     taper_port_name1: str = "o1",
@@ -37,18 +38,31 @@ def add_tapers(
         npoints: number of points.
         linear: shape of the transition, sine when False.
         kwargs: cross_section settings for section2.
+
+    Note:
+        If ``taper`` is a partial function and ``cross_section2`` is None, then
+        ``cross_section2`` is inferred from the partial keywords.
     """
     c = gf.Component()
+    component = gf.get_component(component)
+
     ports_to_taper = select_ports(component.ports) if select_ports else component.ports
     ports_to_taper_names = [p.name for p in ports_to_taper.values()]
 
     for port_name, port in component.ports.items():
         if port.name in ports_to_taper_names:
-            taper_ref = c << taper(
-                cross_section1=port.cross_section,
-                cross_section2=cross_section2,
-                **kwargs,
-            )
+            if isinstance(taper, partial) and cross_section2 is None:
+                taper_ref = c << taper(
+                    cross_section2=partial(
+                        taper.keywords["cross_section2"], width=port.width
+                    ),
+                )
+            else:
+                taper_ref = c << taper(
+                    cross_section1=port.cross_section,
+                    cross_section2=cross_section2,
+                    **kwargs,
+                )
             taper_ref.connect(taper_ref.ports[taper_port_name1].name, port)
             c.add_port(name=port_name, port=taper_ref.ports[taper_port_name2])
         else:
diff --git a/gdsfactory/components/taper_cross_section.py b/gdsfactory/components/taper_cross_section.py
index 009d79efda..3ef2f406a3 100644
--- a/gdsfactory/components/taper_cross_section.py
+++ b/gdsfactory/components/taper_cross_section.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from functools import partial
+from itertools import islice
 
 import gdsfactory as gf
 from gdsfactory.cell import cell
@@ -57,6 +58,19 @@ def taper_cross_section(
     ref = c << gf.path.extrude_transition(taper_path, transition=transition)
     c.add_ports(ref.ports)
     c.absorb(ref)
+
+    # set one pin for each cross section
+    x1.add_pins(
+        c,
+        select_ports=lambda ports: {(port_name := next(iter(ports))): ports[port_name]},
+    )
+    x2.add_pins(
+        c,
+        select_ports=lambda ports: {
+            (port_name := next(islice(iter(ports), 1, None))): ports[port_name],
+        },
+    )
+
     if "type" in x1.info and x1.info["type"] == x2.info.get("type"):
         c.add_route_info(cross_section=x1, length=length, taper=True)
     return c
@@ -68,7 +82,6 @@ def taper_cross_section(
     taper_cross_section, linear=False, width_type="parabolic", npoints=101
 )
 
-
 if __name__ == "__main__":
     # x1 = partial(strip, width=0.5)
     # x2 = partial(strip, width=2.5)
diff --git a/gdsfactory/cross_section.py b/gdsfactory/cross_section.py
index ab8286cf34..946e8370ed 100644
--- a/gdsfactory/cross_section.py
+++ b/gdsfactory/cross_section.py
@@ -289,7 +289,10 @@ def mirror(self) -> CrossSection:
         sections = [s.model_copy(update=dict(offset=-s.offset)) for s in self.sections]
         return self.model_copy(update={"sections": tuple(sections)})
 
-    def add_pins(self, component: Component) -> Component:
+    def add_pins(self, component: Component, *args, **kwargs) -> Component:
+        """Add pins to a target component according to :class:`CrossSection`.
+        Args and kwargs are passed to the function defined by the `add_pins_function_name`.
+        """
         if self.add_pins_function_name is None:
             return component
 
@@ -300,7 +303,7 @@ def add_pins(self, component: Component) -> Component:
                 f"add_pins_function_module = {self.add_pins_function_module}"
             )
         function = getattr(add_pins, self.add_pins_function_name)
-        return function(component=component)
+        return function(*args, component=component, **kwargs)
 
     def add_bbox(
         self,