From 9cd858a0effd81162dfd4d5d48e5a693833abcf4 Mon Sep 17 00:00:00 2001
From: mcc <andi.m.mcclure@gmail.com>
Date: Sat, 25 Apr 2020 18:32:48 -0400
Subject: [PATCH] Add tests to identity-quat patch and also take an axis not a
 full value for the identity fallback

---
 modules/quat.lua   | 13 +++++++------
 spec/quat_spec.lua | 16 ++++++++++++++++
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/modules/quat.lua b/modules/quat.lua
index 8b01421..0e1bace 100644
--- a/modules/quat.lua
+++ b/modules/quat.lua
@@ -364,12 +364,12 @@ end
 
 --- Convert a quaternion into an angle plus axis components.
 -- @tparam quat a Quaternion to convert
--- @tparam identity an optional table to return on identity/degenerate quaternions (by default returns 0,0,0,1)
+-- @tparam identityAxis vec3 of axis to use on identity/degenerate quaternions (optional, default returns 0,0,0,1)
 -- @treturn number angle
 -- @treturn x axis-x
 -- @treturn y axis-y
 -- @treturn z axis-z
-function quat.to_angle_axis_unpack(a, identity)
+function quat.to_angle_axis_unpack(a, identityAxis)
 	if a.w > 1 or a.w < -1 then
 		a = a:normalize()
 	end
@@ -378,8 +378,8 @@ function quat.to_angle_axis_unpack(a, identity)
 	-- Normally an identity quat would return a nonsense answer, so we return an arbitrary zero rotation early.
 	-- FIXME: Is it safe to assume there are *no* valid quaternions with nonzero degenerate lengths?
 	if a.x*a.x + a.y*a.y + a.z*a.z < constants.DBL_EPSILON*constants.DBL_EPSILON then
-		if identity then
-			return unpack(identity)
+		if identityAxis then
+			return 0,identityAxis:unpack()
 		else
 			return 0,0,0,1
 		end
@@ -404,10 +404,11 @@ end
 
 --- Convert a quaternion into an angle/axis pair.
 -- @tparam quat a Quaternion to convert
+-- @tparam identityAxis vec3 of axis to use on identity/degenerate quaternions (optional, default returns 0,vec3(0,0,1))
 -- @treturn number angle
 -- @treturn vec3 axis
-function quat.to_angle_axis(a, default)
-	local angle, x, y, z = a:to_angle_axis_unpack(default)
+function quat.to_angle_axis(a, identityAxis)
+	local angle, x, y, z = a:to_angle_axis_unpack(identityAxis)
 	return angle, vec3(x, y, z)
 end
 
diff --git a/spec/quat_spec.lua b/spec/quat_spec.lua
index ecb2b8a..9867dc8 100644
--- a/spec/quat_spec.lua
+++ b/spec/quat_spec.lua
@@ -310,6 +310,22 @@ describe("quat:", function()
 		assert.is.equal(3, axis.z)
 	end)
 
+	it("converts between a quaternion and angle/axis (identity quaternion) (by component)", function()
+		local angle, x,y,z = quat():to_angle_axis_unpack()
+		assert.is.equal(0, angle)
+		assert.is.equal(0, x)
+		assert.is.equal(0, y)
+		assert.is.equal(1, z)
+	end)
+
+	it("converts between a quaternion and angle/axis (identity quaternion with fallback)", function()
+		local angle, axis = quat():to_angle_axis(vec3(2,3,4))
+		assert.is.equal(0, angle)
+		assert.is.equal(2, axis.x)
+		assert.is.equal(3, axis.y)
+		assert.is.equal(4, axis.z)
+	end)
+
 	it("gets a string representation of a quaternion", function()
 		local a = quat():to_string()
 		assert.is.equal("(+0.000,+0.000,+0.000,+1.000)", a)