66 files changed, 301 insertions, 22 deletions
diff --git a/toolkit/components/uniffi-fixtures/arithmetic/Cargo.toml b/toolkit/components/uniffi-fixtures/arithmetic/Cargo.toml
new file mode 100644
index 0000000000..b497b8cccc
--- /dev/null
+++ b/toolkit/components/uniffi-fixtures/arithmetic/Cargo.toml
@@ -0,0 +1,21 @@
+[package]
+name = "uniffi-example-arithmetic"
+edition = "2021"
+version = "0.22.0"
+authors = ["Firefox Sync Team <sync-team@mozilla.com>"]
+license = "MPL-2.0"
+publish = false
+
+[lib]
+crate-type = ["lib", "cdylib"]
+name = "arithmetical"
+
+[dependencies]
+uniffi = { workspace = true }
+thiserror = "1.0"
+
+[build-dependencies]
+uniffi = { workspace = true, features = ["build"] }
+
+[dev-dependencies]
+uniffi = { workspace = true, features = ["bindgen-tests"] }
diff --git a/third_party/rust/uniffi-example-arithmetic/build.rs b/toolkit/components/uniffi-fixtures/arithmetic/build.rs
index 303ac22d8d..303ac22d8d 100644
--- a/third_party/rust/uniffi-example-arithmetic/build.rs
+++ b/toolkit/components/uniffi-fixtures/arithmetic/build.rs
diff --git a/third_party/rust/uniffi-example-arithmetic/src/arithmetic.udl b/toolkit/components/uniffi-fixtures/arithmetic/src/arithmetic.udl
index 117df4834a..117df4834a 100644
--- a/third_party/rust/uniffi-example-arithmetic/src/arithmetic.udl
+++ b/toolkit/components/uniffi-fixtures/arithmetic/src/arithmetic.udl
diff --git a/third_party/rust/uniffi-example-arithmetic/src/lib.rs b/toolkit/components/uniffi-fixtures/arithmetic/src/lib.rs
index 92ab8c072b..92ab8c072b 100644
--- a/third_party/rust/uniffi-example-arithmetic/src/lib.rs
+++ b/toolkit/components/uniffi-fixtures/arithmetic/src/lib.rs
diff --git a/third_party/rust/uniffi-example-arithmetic/tests/bindings/test_arithmetic.kts b/toolkit/components/uniffi-fixtures/arithmetic/tests/bindings/test_arithmetic.kts
index ef11850ae2..ef11850ae2 100644
--- a/third_party/rust/uniffi-example-arithmetic/tests/bindings/test_arithmetic.kts
+++ b/toolkit/components/uniffi-fixtures/arithmetic/tests/bindings/test_arithmetic.kts
diff --git a/toolkit/components/uniffi-fixtures/arithmetic/tests/bindings/test_arithmetic.py b/toolkit/components/uniffi-fixtures/arithmetic/tests/bindings/test_arithmetic.py
new file mode 100644
index 0000000000..e1b4f71277
--- /dev/null
+++ b/toolkit/components/uniffi-fixtures/arithmetic/tests/bindings/test_arithmetic.py
@@ -0,0 +1,37 @@
+from arithmetic import InternalError, add, div, equal, sub
+
+try:
+    add(18446744073709551615, 1)
+    assert not ("Should have thrown a IntegerOverflow exception!")
+except ArithmeticError.IntegerOverflow:
+    # It's okay!
+    pass
+
+assert add(2, 4) == 6
+assert add(4, 8) == 12
+
+try:
+    sub(0, 1)
+    assert not ("Should have thrown a IntegerOverflow exception!")
+except ArithmeticError.IntegerOverflow:
+    # It's okay!
+    pass
+
+assert sub(4, 2) == 2
+assert sub(8, 4) == 4
+
+assert div(8, 4) == 2
+
+try:
+    div(8, 0)
+except InternalError:
+    # It's okay!
+    pass
+else:
+    assert not ("Should have panicked when dividing by zero")
+
+assert equal(2, 2)
+assert equal(4, 4)
+
+assert not equal(2, 4)
+assert not equal(4, 8)
diff --git a/third_party/rust/uniffi-example-arithmetic/tests/bindings/test_arithmetic.rb b/toolkit/components/uniffi-fixtures/arithmetic/tests/bindings/test_arithmetic.rb
index 6669eb279f..6669eb279f 100644
--- a/third_party/rust/uniffi-example-arithmetic/tests/bindings/test_arithmetic.rb
+++ b/toolkit/components/uniffi-fixtures/arithmetic/tests/bindings/test_arithmetic.rb
diff --git a/third_party/rust/uniffi-example-arithmetic/tests/bindings/test_arithmetic.swift b/toolkit/components/uniffi-fixtures/arithmetic/tests/bindings/test_arithmetic.swift
index a8e34680e4..a8e34680e4 100644
--- a/third_party/rust/uniffi-example-arithmetic/tests/bindings/test_arithmetic.swift
+++ b/toolkit/components/uniffi-fixtures/arithmetic/tests/bindings/test_arithmetic.swift
diff --git a/third_party/rust/uniffi-example-arithmetic/tests/test_generated_bindings.rs b/toolkit/components/uniffi-fixtures/arithmetic/tests/test_generated_bindings.rs
index 168e6e1d4c..168e6e1d4c 100644
--- a/third_party/rust/uniffi-example-arithmetic/tests/test_generated_bindings.rs
+++ b/toolkit/components/uniffi-fixtures/arithmetic/tests/test_generated_bindings.rs
diff --git a/third_party/rust/uniffi-example-arithmetic/uniffi.toml b/toolkit/components/uniffi-fixtures/arithmetic/uniffi.toml
index 883231dcaa..883231dcaa 100644
--- a/third_party/rust/uniffi-example-arithmetic/uniffi.toml
+++ b/toolkit/components/uniffi-fixtures/arithmetic/uniffi.toml
diff --git a/toolkit/components/uniffi-fixture-callbacks/Cargo.toml b/toolkit/components/uniffi-fixtures/callbacks/Cargo.toml
index 19a8d61070..19a8d61070 100644
--- a/toolkit/components/uniffi-fixture-callbacks/Cargo.toml
+++ b/toolkit/components/uniffi-fixtures/callbacks/Cargo.toml
diff --git a/toolkit/components/uniffi-fixture-callbacks/build.rs b/toolkit/components/uniffi-fixtures/callbacks/build.rs
index e7152d922a..e7152d922a 100644
--- a/toolkit/components/uniffi-fixture-callbacks/build.rs
+++ b/toolkit/components/uniffi-fixtures/callbacks/build.rs
diff --git a/toolkit/components/uniffi-fixture-callbacks/src/callbacks.udl b/toolkit/components/uniffi-fixtures/callbacks/src/callbacks.udl
index a6d44ef598..a6d44ef598 100644
--- a/toolkit/components/uniffi-fixture-callbacks/src/callbacks.udl
+++ b/toolkit/components/uniffi-fixtures/callbacks/src/callbacks.udl
diff --git a/toolkit/components/uniffi-fixture-callbacks/src/lib.rs b/toolkit/components/uniffi-fixtures/callbacks/src/lib.rs
index 9ada66bca5..9ada66bca5 100644
--- a/toolkit/components/uniffi-fixture-callbacks/src/lib.rs
+++ b/toolkit/components/uniffi-fixtures/callbacks/src/lib.rs
diff --git a/toolkit/components/uniffi-example-custom-types/Cargo.toml b/toolkit/components/uniffi-fixtures/custom-types/Cargo.toml
index a05324952e..a05324952e 100644
--- a/toolkit/components/uniffi-example-custom-types/Cargo.toml
+++ b/toolkit/components/uniffi-fixtures/custom-types/Cargo.toml
diff --git a/toolkit/components/uniffi-example-custom-types/build.rs b/toolkit/components/uniffi-fixtures/custom-types/build.rs
index 10b6d220da..10b6d220da 100644
--- a/toolkit/components/uniffi-example-custom-types/build.rs
+++ b/toolkit/components/uniffi-fixtures/custom-types/build.rs
diff --git a/toolkit/components/uniffi-example-custom-types/src/custom-types.udl b/toolkit/components/uniffi-fixtures/custom-types/src/custom-types.udl
index 8fef8ff41a..8fef8ff41a 100644
--- a/toolkit/components/uniffi-example-custom-types/src/custom-types.udl
+++ b/toolkit/components/uniffi-fixtures/custom-types/src/custom-types.udl
diff --git a/toolkit/components/uniffi-example-custom-types/src/lib.rs b/toolkit/components/uniffi-fixtures/custom-types/src/lib.rs
index 61aea7a11a..61aea7a11a 100644
--- a/toolkit/components/uniffi-example-custom-types/src/lib.rs
+++ b/toolkit/components/uniffi-fixtures/custom-types/src/lib.rs
diff --git a/toolkit/components/uniffi-example-custom-types/tests/bindings/test_custom_types.kts b/toolkit/components/uniffi-fixtures/custom-types/tests/bindings/test_custom_types.kts
index d75bd99eee..d75bd99eee 100644
--- a/toolkit/components/uniffi-example-custom-types/tests/bindings/test_custom_types.kts
+++ b/toolkit/components/uniffi-fixtures/custom-types/tests/bindings/test_custom_types.kts
diff --git a/toolkit/components/uniffi-example-custom-types/tests/bindings/test_custom_types.swift b/toolkit/components/uniffi-fixtures/custom-types/tests/bindings/test_custom_types.swift
index 5aaf6ff3b0..5aaf6ff3b0 100644
--- a/toolkit/components/uniffi-example-custom-types/tests/bindings/test_custom_types.swift
+++ b/toolkit/components/uniffi-fixtures/custom-types/tests/bindings/test_custom_types.swift
diff --git a/toolkit/components/uniffi-example-custom-types/tests/test_generated_bindings.rs b/toolkit/components/uniffi-fixtures/custom-types/tests/test_generated_bindings.rs
index 38db89790e..38db89790e 100644
--- a/toolkit/components/uniffi-example-custom-types/tests/test_generated_bindings.rs
+++ b/toolkit/components/uniffi-fixtures/custom-types/tests/test_generated_bindings.rs
diff --git a/toolkit/components/uniffi-example-custom-types/uniffi.toml b/toolkit/components/uniffi-fixtures/custom-types/uniffi.toml
index 873fa090fb..873fa090fb 100644
--- a/toolkit/components/uniffi-example-custom-types/uniffi.toml
+++ b/toolkit/components/uniffi-fixtures/custom-types/uniffi.toml
diff --git a/toolkit/components/uniffi-fixtures/external-types/Cargo.toml b/toolkit/components/uniffi-fixtures/external-types/Cargo.toml
new file mode 100644
index 0000000000..b70673374e
--- /dev/null
+++ b/toolkit/components/uniffi-fixtures/external-types/Cargo.toml
@@ -0,0 +1,15 @@
+[package]
+name = "uniffi-fixture-external-types"
+edition = "2021"
+version = "0.21.0"
+authors = ["Firefox Sync Team <sync-team@mozilla.com>"]
+license = "MPL-2.0"
+publish = false
+
+[dependencies]
+uniffi-example-geometry = { path = "../geometry/" }
+uniffi = { workspace = true }
+thiserror = "1.0"
+
+[build-dependencies]
+uniffi = { workspace = true, features = ["build"] }
diff --git a/toolkit/components/uniffi-fixture-external-types/build.rs b/toolkit/components/uniffi-fixtures/external-types/build.rs
index 13f56ca56b..13f56ca56b 100644
--- a/toolkit/components/uniffi-fixture-external-types/build.rs
+++ b/toolkit/components/uniffi-fixtures/external-types/build.rs
diff --git a/toolkit/components/uniffi-fixture-external-types/src/external-types.udl b/toolkit/components/uniffi-fixtures/external-types/src/external-types.udl
index d50fc680f7..d50fc680f7 100644
--- a/toolkit/components/uniffi-fixture-external-types/src/external-types.udl
+++ b/toolkit/components/uniffi-fixtures/external-types/src/external-types.udl
diff --git a/toolkit/components/uniffi-fixture-external-types/src/lib.rs b/toolkit/components/uniffi-fixtures/external-types/src/lib.rs
index 2d12332312..2d12332312 100644
--- a/toolkit/components/uniffi-fixture-external-types/src/lib.rs
+++ b/toolkit/components/uniffi-fixtures/external-types/src/lib.rs
diff --git a/toolkit/components/uniffi-fixtures/geometry/Cargo.toml b/toolkit/components/uniffi-fixtures/geometry/Cargo.toml
new file mode 100644
index 0000000000..a35ce906aa
--- /dev/null
+++ b/toolkit/components/uniffi-fixtures/geometry/Cargo.toml
@@ -0,0 +1,20 @@
+[package]
+name = "uniffi-example-geometry"
+edition = "2021"
+version = "0.22.0"
+authors = ["Firefox Sync Team <sync-team@mozilla.com>"]
+license = "MPL-2.0"
+publish = false
+
+[lib]
+crate-type = ["lib", "cdylib"]
+name = "uniffi_geometry"
+
+[dependencies]
+uniffi = { workspace = true }
+
+[build-dependencies]
+uniffi = { workspace = true, features = ["build"] }
+
+[dev-dependencies]
+uniffi = { workspace = true, features = ["bindgen-tests"] }
diff --git a/third_party/rust/uniffi-example-geometry/build.rs b/toolkit/components/uniffi-fixtures/geometry/build.rs
index 2dd1c96bc3..2dd1c96bc3 100644
--- a/third_party/rust/uniffi-example-geometry/build.rs
+++ b/toolkit/components/uniffi-fixtures/geometry/build.rs
diff --git a/third_party/rust/uniffi-example-geometry/src/geometry.udl b/toolkit/components/uniffi-fixtures/geometry/src/geometry.udl
index af60d429bf..af60d429bf 100644
--- a/third_party/rust/uniffi-example-geometry/src/geometry.udl
+++ b/toolkit/components/uniffi-fixtures/geometry/src/geometry.udl
diff --git a/third_party/rust/uniffi-example-geometry/src/lib.rs b/toolkit/components/uniffi-fixtures/geometry/src/lib.rs
index d710b150bb..d710b150bb 100644
--- a/third_party/rust/uniffi-example-geometry/src/lib.rs
+++ b/toolkit/components/uniffi-fixtures/geometry/src/lib.rs
diff --git a/third_party/rust/uniffi-example-geometry/tests/bindings/test_geometry.kts b/toolkit/components/uniffi-fixtures/geometry/tests/bindings/test_geometry.kts
index 77bb9932ec..77bb9932ec 100644
--- a/third_party/rust/uniffi-example-geometry/tests/bindings/test_geometry.kts
+++ b/toolkit/components/uniffi-fixtures/geometry/tests/bindings/test_geometry.kts
diff --git a/third_party/rust/uniffi-example-geometry/tests/bindings/test_geometry.py b/toolkit/components/uniffi-fixtures/geometry/tests/bindings/test_geometry.py
index fd6772be24..bfb6560626 100644
--- a/third_party/rust/uniffi-example-geometry/tests/bindings/test_geometry.py
+++ b/toolkit/components/uniffi-fixtures/geometry/tests/bindings/test_geometry.py
@@ -1,4 +1,4 @@
-from geometry import *
+from geometry import Line, Point, gradient, intersection
 
 ln1 = Line(start=Point(coord_x=0, coord_y=0), end=Point(coord_x=1, coord_y=2))
 ln2 = Line(start=Point(coord_x=1, coord_y=1), end=Point(coord_x=2, coord_y=2))
diff --git a/third_party/rust/uniffi-example-geometry/tests/bindings/test_geometry.rb b/toolkit/components/uniffi-fixtures/geometry/tests/bindings/test_geometry.rb
index 90fdff684e..90fdff684e 100644
--- a/third_party/rust/uniffi-example-geometry/tests/bindings/test_geometry.rb
+++ b/toolkit/components/uniffi-fixtures/geometry/tests/bindings/test_geometry.rb
diff --git a/third_party/rust/uniffi-example-geometry/tests/bindings/test_geometry.swift b/toolkit/components/uniffi-fixtures/geometry/tests/bindings/test_geometry.swift
index 58bd65607f..58bd65607f 100644
--- a/third_party/rust/uniffi-example-geometry/tests/bindings/test_geometry.swift
+++ b/toolkit/components/uniffi-fixtures/geometry/tests/bindings/test_geometry.swift
diff --git a/third_party/rust/uniffi-example-geometry/tests/test_generated_bindings.rs b/toolkit/components/uniffi-fixtures/geometry/tests/test_generated_bindings.rs
index 4638d847c8..4638d847c8 100644
--- a/third_party/rust/uniffi-example-geometry/tests/test_generated_bindings.rs
+++ b/toolkit/components/uniffi-fixtures/geometry/tests/test_generated_bindings.rs
diff --git a/toolkit/components/uniffi-fixture-refcounts/Cargo.toml b/toolkit/components/uniffi-fixtures/refcounts/Cargo.toml
index 877e502711..877e502711 100644
--- a/toolkit/components/uniffi-fixture-refcounts/Cargo.toml
+++ b/toolkit/components/uniffi-fixtures/refcounts/Cargo.toml
diff --git a/toolkit/components/uniffi-fixture-refcounts/build.rs b/toolkit/components/uniffi-fixtures/refcounts/build.rs
index 9ea03e12de..9ea03e12de 100644
--- a/toolkit/components/uniffi-fixture-refcounts/build.rs
+++ b/toolkit/components/uniffi-fixtures/refcounts/build.rs
diff --git a/toolkit/components/uniffi-fixtures/refcounts/src/lib.rs b/toolkit/components/uniffi-fixtures/refcounts/src/lib.rs
new file mode 100644
index 0000000000..6554625c62
--- /dev/null
+++ b/toolkit/components/uniffi-fixtures/refcounts/src/lib.rs
@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/// This crate exists to test managing the Rust Arc strong counts as JS objects are
+/// created/destroyed.  See `test_refcounts.js` for how it's used.
+use std::sync::{Arc, Mutex};
+
+pub struct SingletonObject;
+
+impl SingletonObject {
+    pub fn method(&self) {}
+}
+
+static SINGLETON: Mutex<Option<Arc<SingletonObject>>> = Mutex::new(None);
+
+pub fn get_singleton() -> Arc<SingletonObject> {
+    Arc::clone(
+        SINGLETON
+            .lock()
+            .unwrap()
+            .get_or_insert_with(|| Arc::new(SingletonObject)),
+    )
+}
+
+pub fn get_js_refcount() -> i32 {
+    // Subtract 2: one for the reference in the Mutex and one for the temporary reference that
+    // we're calling Arc::strong_count on.
+    (Arc::strong_count(&get_singleton()) as i32) - 2
+}
+
+include!(concat!(env!("OUT_DIR"), "/refcounts.uniffi.rs"));
diff --git a/toolkit/components/uniffi-fixture-refcounts/src/refcounts.udl b/toolkit/components/uniffi-fixtures/refcounts/src/refcounts.udl
index 25ec83cfcc..25ec83cfcc 100644
--- a/toolkit/components/uniffi-fixture-refcounts/src/refcounts.udl
+++ b/toolkit/components/uniffi-fixtures/refcounts/src/refcounts.udl
diff --git a/toolkit/components/uniffi-fixtures/rondpoint/Cargo.toml b/toolkit/components/uniffi-fixtures/rondpoint/Cargo.toml
new file mode 100644
index 0000000000..1d0be84785
--- /dev/null
+++ b/toolkit/components/uniffi-fixtures/rondpoint/Cargo.toml
@@ -0,0 +1,20 @@
+[package]
+name = "uniffi-example-rondpoint"
+edition = "2021"
+version = "0.22.0"
+authors = ["Firefox Sync Team <sync-team@mozilla.com>"]
+license = "MPL-2.0"
+publish = false
+
+[lib]
+crate-type = ["lib", "cdylib"]
+name = "uniffi_rondpoint"
+
+[dependencies]
+uniffi = { workspace = true }
+
+[build-dependencies]
+uniffi = { workspace = true, features = ["build"] }
+
+[dev-dependencies]
+uniffi = { workspace = true, features = ["bindgen-tests"] }
diff --git a/third_party/rust/uniffi-example-rondpoint/build.rs b/toolkit/components/uniffi-fixtures/rondpoint/build.rs
index f830879d09..f830879d09 100644
--- a/third_party/rust/uniffi-example-rondpoint/build.rs
+++ b/toolkit/components/uniffi-fixtures/rondpoint/build.rs
diff --git a/third_party/rust/uniffi-example-rondpoint/src/lib.rs b/toolkit/components/uniffi-fixtures/rondpoint/src/lib.rs
index 3f2233ddaa..3f2233ddaa 100644
--- a/third_party/rust/uniffi-example-rondpoint/src/lib.rs
+++ b/toolkit/components/uniffi-fixtures/rondpoint/src/lib.rs
diff --git a/third_party/rust/uniffi-example-rondpoint/src/rondpoint.udl b/toolkit/components/uniffi-fixtures/rondpoint/src/rondpoint.udl
index 7c8261d74e..7c8261d74e 100644
--- a/third_party/rust/uniffi-example-rondpoint/src/rondpoint.udl
+++ b/toolkit/components/uniffi-fixtures/rondpoint/src/rondpoint.udl
diff --git a/third_party/rust/uniffi-example-rondpoint/tests/bindings/test_rondpoint.kts b/toolkit/components/uniffi-fixtures/rondpoint/tests/bindings/test_rondpoint.kts
index cc5ddf2a86..cc5ddf2a86 100644
--- a/third_party/rust/uniffi-example-rondpoint/tests/bindings/test_rondpoint.kts
+++ b/toolkit/components/uniffi-fixtures/rondpoint/tests/bindings/test_rondpoint.kts
diff --git a/third_party/rust/uniffi-example-rondpoint/tests/bindings/test_rondpoint.py b/toolkit/components/uniffi-fixtures/rondpoint/tests/bindings/test_rondpoint.py
index 0b47c0fa5a..df3e3fab18 100644
--- a/third_party/rust/uniffi-example-rondpoint/tests/bindings/test_rondpoint.py
+++ b/toolkit/components/uniffi-fixtures/rondpoint/tests/bindings/test_rondpoint.py
@@ -1,18 +1,37 @@
-import sys
 import ctypes
-from rondpoint import *
+import sys
 
-dico = Dictionnaire(un=Enumeration.DEUX, deux=True, petit_nombre=0, gros_nombre=123456789)
+from rondpoint import (
+    Dictionnaire,
+    Enumeration,
+    EnumerationAvecDonnees,
+    Retourneur,
+    Stringifier,
+    copie_carte,
+    copie_dictionnaire,
+    copie_enumeration,
+    copie_enumerations,
+    switcheroo,
+)
+
+dico = Dictionnaire(
+    un=Enumeration.DEUX, deux=True, petit_nombre=0, gros_nombre=123456789
+)
 copyDico = copie_dictionnaire(dico)
 assert dico == copyDico
 
 assert copie_enumeration(Enumeration.DEUX) == Enumeration.DEUX
-assert copie_enumerations([Enumeration.UN, Enumeration.DEUX]) == [Enumeration.UN, Enumeration.DEUX]
-assert copie_carte({
-    "0": EnumerationAvecDonnees.ZERO(),
-    "1": EnumerationAvecDonnees.UN(1),
-    "2": EnumerationAvecDonnees.DEUX(2, "deux"),
-}) == {
+assert copie_enumerations([Enumeration.UN, Enumeration.DEUX]) == [
+    Enumeration.UN,
+    Enumeration.DEUX,
+]
+assert copie_carte(
+    {
+        "0": EnumerationAvecDonnees.ZERO(),
+        "1": EnumerationAvecDonnees.UN(1),
+        "2": EnumerationAvecDonnees.DEUX(2, "deux"),
+    }
+) == {
     "0": EnumerationAvecDonnees.ZERO(),
     "1": EnumerationAvecDonnees.UN(1),
     "2": EnumerationAvecDonnees.DEUX(2, "deux"),
@@ -30,11 +49,13 @@ assert EnumerationAvecDonnees.UN(1) != EnumerationAvecDonnees.UN(2)
 #      lowering from rust and lifting into python.
 rt = Retourneur()
 
+
 def affirmAllerRetour(vals, identique):
     for v in vals:
         id_v = identique(v)
         assert id_v == v, f"Round-trip failure: {v} => {id_v}"
 
+
 MIN_I8 = -1 * 2**7
 MAX_I8 = 2**7 - 1
 MIN_I16 = -1 * 2**15
@@ -65,21 +86,29 @@ affirmAllerRetour([0x00000000, 0x12345678, 0xFFFFFFFF], rt.identique_u32)
 
 # Longs
 affirmAllerRetour([MIN_I64, -1, 0, 1, MAX_I64], rt.identique_i64)
-affirmAllerRetour([0x0000000000000000, 0x1234567890ABCDEF, 0xFFFFFFFFFFFFFFFF], rt.identique_u64)
+affirmAllerRetour(
+    [0x0000000000000000, 0x1234567890ABCDEF, 0xFFFFFFFFFFFFFFFF], rt.identique_u64
+)
 
 # Floats
 affirmAllerRetour([0.0, 0.5, 0.25, 1.0, F32_ONE_THIRD], rt.identique_float)
 
 # Doubles
 affirmAllerRetour(
-  [0.0, 0.5, 0.25, 1.0, 1.0 / 3, sys.float_info.max, sys.float_info.min],
-  rt.identique_double
+    [0.0, 0.5, 0.25, 1.0, 1.0 / 3, sys.float_info.max, sys.float_info.min],
+    rt.identique_double,
 )
 
 # Strings
 affirmAllerRetour(
-  ["", "abc", "été", "ښي لاس ته لوستلو لوستل", "😻emoji 👨‍👧‍👦multi-emoji, 🇨🇭a flag, a canal, panama"],
-  rt.identique_string
+    [
+        "",
+        "abc",
+        "été",
+        "ښي لاس ته لوستلو لوستل",
+        "😻emoji 👨‍👧‍👦multi-emoji, 🇨🇭a flag, a canal, panama",
+    ],
+    rt.identique_string,
 )
 
 # Test one way across the FFI.
@@ -97,11 +126,13 @@ affirmAllerRetour(
 # together, we've shown the correctness of the return leg.
 st = Stringifier()
 
+
 def affirmEnchaine(vals, toString, rustyStringify=lambda v: str(v).lower()):
     for v in vals:
         str_v = toString(v)
         assert rustyStringify(v) == str_v, f"String compare error {v} => {str_v}"
 
+
 # Test the efficacy of the string transport from rust. If this fails, but everything else
 # works, then things are very weird.
 wellKnown = st.well_known_string("python")
@@ -124,7 +155,10 @@ affirmEnchaine([0x00000000, 0x12345678, 0xFFFFFFFF], st.to_string_u32)
 
 # Longs
 affirmEnchaine([MIN_I64, -1, 0, 1, MAX_I64], st.to_string_i64)
-affirmEnchaine([0x0000000000000000, 0x1234567890ABCDEF, 0xFFFFFFFFFFFFFFFF], st.to_string_u64)
+affirmEnchaine(
+    [0x0000000000000000, 0x1234567890ABCDEF, 0xFFFFFFFFFFFFFFFF], st.to_string_u64
+)
+
 
 # Floats
 def rustyFloatToStr(v):
@@ -134,13 +168,16 @@ def rustyFloatToStr(v):
         return str(int(v))
     return str(v)
 
+
 affirmEnchaine([0.0, 0.5, 0.25, 1.0], st.to_string_float, rustyFloatToStr)
-assert st.to_string_float(F32_ONE_THIRD) == "0.33333334" # annoyingly different string repr
+assert (
+    st.to_string_float(F32_ONE_THIRD) == "0.33333334"
+)  # annoyingly different string repr
 
 # Doubles
 # TODO: float_info.max/float_info.min don't stringify-roundtrip properly yet, TBD.
 affirmEnchaine(
-  [0.0, 0.5, 0.25, 1.0, 1.0 / 3],
-  st.to_string_double,
-  rustyFloatToStr,
+    [0.0, 0.5, 0.25, 1.0, 1.0 / 3],
+    st.to_string_double,
+    rustyFloatToStr,
 )
diff --git a/third_party/rust/uniffi-example-rondpoint/tests/bindings/test_rondpoint.rb b/toolkit/components/uniffi-fixtures/rondpoint/tests/bindings/test_rondpoint.rb
index faa4062019..faa4062019 100644
--- a/third_party/rust/uniffi-example-rondpoint/tests/bindings/test_rondpoint.rb
+++ b/toolkit/components/uniffi-fixtures/rondpoint/tests/bindings/test_rondpoint.rb
diff --git a/third_party/rust/uniffi-example-rondpoint/tests/bindings/test_rondpoint.swift b/toolkit/components/uniffi-fixtures/rondpoint/tests/bindings/test_rondpoint.swift
index d9f47058ed..d9f47058ed 100644
--- a/third_party/rust/uniffi-example-rondpoint/tests/bindings/test_rondpoint.swift
+++ b/toolkit/components/uniffi-fixtures/rondpoint/tests/bindings/test_rondpoint.swift
diff --git a/third_party/rust/uniffi-example-rondpoint/tests/test_generated_bindings.rs b/toolkit/components/uniffi-fixtures/rondpoint/tests/test_generated_bindings.rs
index d337374334..d337374334 100644
--- a/third_party/rust/uniffi-example-rondpoint/tests/test_generated_bindings.rs
+++ b/toolkit/components/uniffi-fixtures/rondpoint/tests/test_generated_bindings.rs
diff --git a/toolkit/components/uniffi-fixtures/sprites/Cargo.toml b/toolkit/components/uniffi-fixtures/sprites/Cargo.toml
new file mode 100644
index 0000000000..3b4f96e143
--- /dev/null
+++ b/toolkit/components/uniffi-fixtures/sprites/Cargo.toml
@@ -0,0 +1,20 @@
+[package]
+name = "uniffi-example-sprites"
+edition = "2021"
+version = "0.22.0"
+authors = ["Firefox Sync Team <sync-team@mozilla.com>"]
+license = "MPL-2.0"
+publish = false
+
+[lib]
+crate-type = ["lib", "cdylib"]
+name = "uniffi_sprites"
+
+[dependencies]
+uniffi = { workspace = true }
+
+[build-dependencies]
+uniffi = { workspace = true, features = ["build"] }
+
+[dev-dependencies]
+uniffi = { workspace = true, features = ["bindgen-tests"] }
diff --git a/third_party/rust/uniffi-example-sprites/build.rs b/toolkit/components/uniffi-fixtures/sprites/build.rs
index 26ac3085b8..26ac3085b8 100644
--- a/third_party/rust/uniffi-example-sprites/build.rs
+++ b/toolkit/components/uniffi-fixtures/sprites/build.rs
diff --git a/third_party/rust/uniffi-example-sprites/src/lib.rs b/toolkit/components/uniffi-fixtures/sprites/src/lib.rs
index d3cc11e408..d3cc11e408 100644
--- a/third_party/rust/uniffi-example-sprites/src/lib.rs
+++ b/toolkit/components/uniffi-fixtures/sprites/src/lib.rs
diff --git a/third_party/rust/uniffi-example-sprites/src/sprites.udl b/toolkit/components/uniffi-fixtures/sprites/src/sprites.udl
index 6781c6cee5..6781c6cee5 100644
--- a/third_party/rust/uniffi-example-sprites/src/sprites.udl
+++ b/toolkit/components/uniffi-fixtures/sprites/src/sprites.udl
diff --git a/third_party/rust/uniffi-example-sprites/tests/bindings/test_sprites.kts b/toolkit/components/uniffi-fixtures/sprites/tests/bindings/test_sprites.kts
index 42451f28dd..42451f28dd 100644
--- a/third_party/rust/uniffi-example-sprites/tests/bindings/test_sprites.kts
+++ b/toolkit/components/uniffi-fixtures/sprites/tests/bindings/test_sprites.kts
diff --git a/third_party/rust/uniffi-example-sprites/tests/bindings/test_sprites.py b/toolkit/components/uniffi-fixtures/sprites/tests/bindings/test_sprites.py
index d04742e076..1e91997001 100644
--- a/third_party/rust/uniffi-example-sprites/tests/bindings/test_sprites.py
+++ b/toolkit/components/uniffi-fixtures/sprites/tests/bindings/test_sprites.py
@@ -1,4 +1,4 @@
-from sprites import *
+from sprites import Point, Sprite, Vector
 
 sempty = Sprite(None)
 assert sempty.get_position() == Point(x=0, y=0)
@@ -14,4 +14,3 @@ assert s.get_position() == Point(x=-3, y=4)
 
 srel = Sprite.new_relative_to(Point(x=0, y=1), Vector(dx=1, dy=1.5))
 assert srel.get_position() == Point(x=1, y=2.5)
-
diff --git a/third_party/rust/uniffi-example-sprites/tests/bindings/test_sprites.rb b/toolkit/components/uniffi-fixtures/sprites/tests/bindings/test_sprites.rb
index fa73043979..fa73043979 100644
--- a/third_party/rust/uniffi-example-sprites/tests/bindings/test_sprites.rb
+++ b/toolkit/components/uniffi-fixtures/sprites/tests/bindings/test_sprites.rb
diff --git a/third_party/rust/uniffi-example-sprites/tests/bindings/test_sprites.swift b/toolkit/components/uniffi-fixtures/sprites/tests/bindings/test_sprites.swift
index d5428ac679..d5428ac679 100644
--- a/third_party/rust/uniffi-example-sprites/tests/bindings/test_sprites.swift
+++ b/toolkit/components/uniffi-fixtures/sprites/tests/bindings/test_sprites.swift
diff --git a/third_party/rust/uniffi-example-sprites/tests/test_generated_bindings.rs b/toolkit/components/uniffi-fixtures/sprites/tests/test_generated_bindings.rs
index 00dd779d68..00dd779d68 100644
--- a/third_party/rust/uniffi-example-sprites/tests/test_generated_bindings.rs
+++ b/toolkit/components/uniffi-fixtures/sprites/tests/test_generated_bindings.rs
diff --git a/toolkit/components/uniffi-fixtures/todolist/Cargo.toml b/toolkit/components/uniffi-fixtures/todolist/Cargo.toml
new file mode 100644
index 0000000000..6673d01e07
--- /dev/null
+++ b/toolkit/components/uniffi-fixtures/todolist/Cargo.toml
@@ -0,0 +1,22 @@
+[package]
+name = "uniffi-example-todolist"
+edition = "2021"
+version = "0.22.0"
+authors = ["Firefox Sync Team <sync-team@mozilla.com>"]
+license = "MPL-2.0"
+publish = false
+
+[lib]
+crate-type = ["lib", "cdylib"]
+name = "uniffi_todolist"
+
+[dependencies]
+uniffi = { workspace = true }
+once_cell = "1.12"
+thiserror = "1.0"
+
+[build-dependencies]
+uniffi = { workspace = true, features = ["build"] }
+
+[dev-dependencies]
+uniffi = { workspace = true, features = ["bindgen-tests"] }
diff --git a/third_party/rust/uniffi-example-todolist/build.rs b/toolkit/components/uniffi-fixtures/todolist/build.rs
index 2dd2f68b75..2dd2f68b75 100644
--- a/third_party/rust/uniffi-example-todolist/build.rs
+++ b/toolkit/components/uniffi-fixtures/todolist/build.rs
diff --git a/third_party/rust/uniffi-example-todolist/src/lib.rs b/toolkit/components/uniffi-fixtures/todolist/src/lib.rs
index 11cdc63aee..11cdc63aee 100644
--- a/third_party/rust/uniffi-example-todolist/src/lib.rs
+++ b/toolkit/components/uniffi-fixtures/todolist/src/lib.rs
diff --git a/third_party/rust/uniffi-example-todolist/src/todolist.udl b/toolkit/components/uniffi-fixtures/todolist/src/todolist.udl
index 5c923314cd..5c923314cd 100644
--- a/third_party/rust/uniffi-example-todolist/src/todolist.udl
+++ b/toolkit/components/uniffi-fixtures/todolist/src/todolist.udl
diff --git a/third_party/rust/uniffi-example-todolist/tests/bindings/test_todolist.kts b/toolkit/components/uniffi-fixtures/todolist/tests/bindings/test_todolist.kts
index bb2b292224..bb2b292224 100644
--- a/third_party/rust/uniffi-example-todolist/tests/bindings/test_todolist.kts
+++ b/toolkit/components/uniffi-fixtures/todolist/tests/bindings/test_todolist.kts
diff --git a/toolkit/components/uniffi-fixtures/todolist/tests/bindings/test_todolist.py b/toolkit/components/uniffi-fixtures/todolist/tests/bindings/test_todolist.py
new file mode 100644
index 0000000000..e4e2cda6d6
--- /dev/null
+++ b/toolkit/components/uniffi-fixtures/todolist/tests/bindings/test_todolist.py
@@ -0,0 +1,56 @@
+from todolist import TodoEntry, TodoList, get_default_list, set_default_list
+
+todo = TodoList()
+
+entry = TodoEntry(text="Write bindings for strings in records")
+
+todo.add_item("Write python bindings")
+
+assert todo.get_last() == "Write python bindings"
+
+todo.add_item("Write tests for bindings")
+
+assert todo.get_last() == "Write tests for bindings"
+
+todo.add_entry(entry)
+
+assert todo.get_last() == "Write bindings for strings in records"
+assert todo.get_last_entry().text == "Write bindings for strings in records"
+
+todo.add_item(
+    "Test Ünicode hàndling without an entry can't believe I didn't test this at first 🤣"
+)
+assert (
+    todo.get_last()
+    == "Test Ünicode hàndling without an entry can't believe I didn't test this at first 🤣"
+)
+
+entry2 = TodoEntry(
+    text="Test Ünicode hàndling in an entry can't believe I didn't test this at first 🤣"
+)
+todo.add_entry(entry2)
+assert (
+    todo.get_last_entry().text
+    == "Test Ünicode hàndling in an entry can't believe I didn't test this at first 🤣"
+)
+
+todo2 = TodoList()
+assert todo != todo2
+assert todo is not todo2
+
+assert get_default_list() is None
+
+set_default_list(todo)
+assert todo.get_items() == get_default_list().get_items()
+
+todo2.make_default()
+assert todo2.get_items() == get_default_list().get_items()
+
+todo.add_item("Test liveness after being demoted from default")
+assert todo.get_last() == "Test liveness after being demoted from default"
+
+todo2.add_item("Test shared state through local vs default reference")
+assert (
+    get_default_list().get_last()
+    == "Test shared state through local vs default reference"
+)
diff --git a/third_party/rust/uniffi-example-todolist/tests/bindings/test_todolist.rb b/toolkit/components/uniffi-fixtures/todolist/tests/bindings/test_todolist.rb
index fc1a823f52..fc1a823f52 100644
--- a/third_party/rust/uniffi-example-todolist/tests/bindings/test_todolist.rb
+++ b/toolkit/components/uniffi-fixtures/todolist/tests/bindings/test_todolist.rb
diff --git a/third_party/rust/uniffi-example-todolist/tests/bindings/test_todolist.swift b/toolkit/components/uniffi-fixtures/todolist/tests/bindings/test_todolist.swift
index 6ce72cadb2..6ce72cadb2 100644
--- a/third_party/rust/uniffi-example-todolist/tests/bindings/test_todolist.swift
+++ b/toolkit/components/uniffi-fixtures/todolist/tests/bindings/test_todolist.swift
diff --git a/third_party/rust/uniffi-example-todolist/tests/test_generated_bindings.rs b/toolkit/components/uniffi-fixtures/todolist/tests/test_generated_bindings.rs
index cefdbfe1dc..cefdbfe1dc 100644
--- a/third_party/rust/uniffi-example-todolist/tests/test_generated_bindings.rs
+++ b/toolkit/components/uniffi-fixtures/todolist/tests/test_generated_bindings.rs