geom.Difference returns empty geometry and no error from two valid polygons

[mnovicio]

Problem:

When calling geom.Difference(a, b Geometry) using the following Polygons, no error is returned but the resulting geometry is of type GeometryCollection with empty values.

Geometry A:

{"type":"Polygon","coordinates":[[[-87.62444917095299,41.39729331748811],[-87.62446704222914,41.397301659153754],[-87.62449506935019,41.39731775684101],[-87.62452090105552,41.397335817239],[-87.62454429589731,41.39735567153923],[-87.6245650352042,41.3973771341657],[-87.6245829251253,41.397400004509386],[-87.62459779844208,41.397424068803204],[-87.62460951613143,41.397449102120135],[-87.62461796866529,41.39747487047549],[-87.6246230770344,41.39750113301402],[-87.62462479348707,41.39752764426096],[-87.6246231019755,41.39755415641672],[-87.62461801830612,41.397580421672856],[-87.62460958999183,41.39760619452835],[-87.62456285356899,41.397724210992784],[-87.62455132416264,41.39774894508767],[-87.62453671452448,41.3977727384771],[-87.62451915784027,41.397795374248304],[-87.62449881416285,41.39781664604174],[-87.62447586895344,41.39783635993238],[-87.62445053139074,41.39785433619775],[-87.62442303246401,41.397870410956294],[-87.62439362286723,41.39788443766158],[-87.62436257071374,41.39789628843825],[-87.62433015909178,41.39790585524787],[-87.62429668348378,41.3979130508739],[-87.62426244907233,41.39791780971686],[-87.62422776795812,41.397920088392326],[-87.62419295631425,41.397919866126564],[-87.62415833150395,41.39791714494585],[-87.62412420918706,41.397911949658024],[-87.62412431963479,41.397911970638134],[-87.6240142654138,41.3978910789883],[-87.62397972826206,41.397883133976144],[-87.62397604150179,41.39788197468104],[-87.62397154652997,41.39788163144765],[-87.62393679249253,41.397876372263475],[-87.6238779544157,41.39786520300083],[-87.62384341726417,41.3978572579968],[-87.6238100933212,41.39784677934415],[-87.62377830950128,41.397833869840746],[-87.62377439835728,41.39783188189482],[-87.62374847092677,41.39782212145373],[-87.62371745215871,41.397807336601254],[-87.62368856511434,41.397790277980455],[-87.62366210264413,41.397771118528894],[-87.62364238065591,41.39775363973907],[-87.62363973273321,41.3977514470298],[-87.62363850541901,41.39775020527393],[-87.62363833301796,41.39775005248186],[-87.62363806435583,41.39774975902078],[-87.6236183787311,41.3977298417487],[-87.62359993880196,41.397706764993615],[-87.62358459039267,41.39768243883536],[-87.62357248119949,41.39765709736778],[-87.62356372774683,41.3976309844548],[-87.62355841426607,41.39760435138386],[-87.62355659188512,41.3975774544476],[-87.62355827813658,41.39755055247751],[-87.62356345678923,41.39752390435329],[-87.62357207800432,41.39749776651146],[-87.6236187070669,41.39738117370699],[-87.62363074852786,41.397355686766915],[-87.62364606262244,41.39733121587506],[-87.62366450066513,41.39730799861518],[-87.62368588364099,41.39728626039952],[-87.62371000394393,41.3972662122803],[-87.62373662739223,41.397248048900735],[-87.62376549550245,41.39723194660534],[-87.62379632799865,41.3972180617278],[-87.62382882553379,41.39720652907334],[-87.62386267259592,41.397197460609846],[-87.62389754057125,41.397190944380924],[-87.62393309093454,41.39718704365108],[-87.62396897853569,41.39718579629156],[-87.62400485495054,41.39718721441263],[-87.62400561478837,41.397187301481495],[-87.62400775375312,41.39718708148513],[-87.6240424599759,41.39718602384076],[-87.6240771423665,41.39718745779836],[-87.62411148616091,41.39719137034386],[-87.62414517966795,41.39719772596847],[-87.62423643421413,41.3972184638187],[-87.6242932704773,41.39722944573794],[-87.62432844349291,41.39723768847929],[-87.62436233243534,41.39724856156757],[-87.62439459138113,41.397261954015285],[-87.62442489104455,41.39727772911831],[-87.62444917095299,41.39729331748811]]]}

Geometry B:

{"type":"Polygon","coordinates":[[[-87.6242938761274,41.39744938185984],[-87.62429387983731,41.3974493827643],[-87.62430377142961,41.397452198873204],[-87.6243132556424,41.39745572107071],[-87.62432224382728,41.39745991643503],[-87.6243306519721,41.39746474575231],[-87.62433840148628,41.397470163883234],[-87.6243454199354,41.397476120184834],[-87.62435164171818,41.39748255898387],[-87.62435700867968,41.39748942009721],[-87.62436147065489,41.39749663939436],[-87.62436498593763,41.397504149396866],[-87.6243675216704,41.39751187990905],[-87.6243690541514,41.397519758674136],[-87.62436956905626,41.39752771204957],[-87.62436906157178,41.39753566569541],[-87.62436753644107,41.397543545269144],[-87.6243650079191,41.39755127712062],[-87.62431827109069,41.397669293489656],[-87.6243148122446,41.39767671371113],[-87.62431042933302,41.397683851719385],[-87.62430516231241,41.39769064244089],[-87.62429905919917,41.397697023968156],[-87.62429217563205,41.39770293812402],[-87.62428457436476,41.3977083309922],[-87.6242763246941,41.397713153408624],[-87.62426750182793,41.39771736140979],[-87.62425818619981,41.39772091663344],[-87.6242484627356,41.39772378666837],[-87.62423842007912,41.39772594534997],[-87.62422814978432,41.39772737299857],[-87.62421774548025,41.39772805659901],[-87.62420730201784,41.39772798991927],[-87.62419691460487,41.3977271735672],[-87.62418667793823,41.3977256149851],[-87.62418671102395,41.3977256212699],[-87.62407665709884,41.39770472967701],[-87.62406629597992,41.397702346179805],[-87.62405629881992,41.397699202590374],[-87.62405211939647,41.3976975050517],[-87.62403011344777,41.397692436957406],[-87.62402019045922,41.39769240856049],[-87.62400961007666,41.39769160064994],[-87.6239991838944,41.39769002289897],[-87.62394034597573,41.397678853666775],[-87.62392998485687,41.397676470172],[-87.6239199876966,41.39767332658449],[-87.62391045256837,41.39766945374326],[-87.62390147301304,41.3976648896414],[-87.62389709425379,41.39766215257271],[-87.62389409652785,41.397661423260395],[-87.6238838004308,41.39765847960019],[-87.62387394964163,41.3976547712504],[-87.62386464402535,41.397650335805466],[-87.62385597792006,41.3976452182309],[-87.62384803918056,41.397639470407476],[-87.62384090828776,41.3976331506053],[-87.623839286541,41.39763137916821],[-87.62383675849487,41.397629285732634],[-87.62383035228544,41.397622804159624],[-87.62382482029217,41.39761588114358],[-87.62382021574966,41.397608583305356],[-87.62381658296758,41.39760098087273],[-87.62381395690413,41.39759314700461],[-87.62381236282981,41.39758515708701],[-87.62381181608414,41.397577088007544],[-87.62381232192811,41.39756901741562],[-87.6238138754936,41.39756102297521],[-87.62381646183007,41.39755318161735],[-87.62386309049305,41.397436588717746],[-87.62386670290655,41.39742894262843],[-87.62387129711452,41.39742160135193],[-87.62387682851207,41.39741463616366],[-87.6238832433953,41.39740811468775],[-87.62389047948277,41.39740210024026],[-87.62389846652009,41.397396651214606],[-87.6239071269621,41.39739182051462],[-87.62391637672572,41.39738765504086],[-87.6239261260062,41.39738419523529],[-87.62393628014925,41.3973814746886],[-87.62394674056974,41.397379519814216],[-87.62395740570904,41.39737834959169],[-87.62396817202092,41.397377975382526],[-87.62397893497695,41.397378400819846],[-87.62398959008122,41.3973796217732],[-87.62400003388497,41.39738162638845],[-87.62400459928844,41.397382685573255],[-87.6240097418674,41.39738137496058],[-87.62401988537127,41.39737957809739],[-87.62403020992313,41.39737851619985],[-87.6240406218205,41.39737819890541],[-87.62405102656818,41.39737862909373],[-87.62406132973588,41.39737980286054],[-87.62407143781516,41.39738170955312],[-87.62416781499175,41.397403611535694],[-87.62422983409283,41.39741559488651],[-87.62424038602445,41.3974180677156],[-87.62425055272993,41.397421329650655],[-87.62426023043129,41.39742534739508],[-87.62426932034207,41.39743007993722],[-87.62427772967571,41.39743547896907],[-87.6242853725927,41.397441489379304],[-87.62429217107669,41.397448049815836],[-87.62429313249845,41.397449200566754],[-87.6242938761274,41.39744938185984]]]}

Using geos.Difference gives the expecting geometry.

Sample Test:

func TestGeometryDiff(t *testing.T) {
	inner := mustGeoJSON(t, `{"type":"Polygon","coordinates":[[[-87.6242938761274,41.39744938185984],[-87.62429387983731,41.3974493827643],[-87.62430377142961,41.397452198873204],[-87.6243132556424,41.39745572107071],[-87.62432224382728,41.39745991643503],[-87.6243306519721,41.39746474575231],[-87.62433840148628,41.397470163883234],[-87.6243454199354,41.397476120184834],[-87.62435164171818,41.39748255898387],[-87.62435700867968,41.39748942009721],[-87.62436147065489,41.39749663939436],[-87.62436498593763,41.397504149396866],[-87.6243675216704,41.39751187990905],[-87.6243690541514,41.397519758674136],[-87.62436956905626,41.39752771204957],[-87.62436906157178,41.39753566569541],[-87.62436753644107,41.397543545269144],[-87.6243650079191,41.39755127712062],[-87.62431827109069,41.397669293489656],[-87.6243148122446,41.39767671371113],[-87.62431042933302,41.397683851719385],[-87.62430516231241,41.39769064244089],[-87.62429905919917,41.397697023968156],[-87.62429217563205,41.39770293812402],[-87.62428457436476,41.3977083309922],[-87.6242763246941,41.397713153408624],[-87.62426750182793,41.39771736140979],[-87.62425818619981,41.39772091663344],[-87.6242484627356,41.39772378666837],[-87.62423842007912,41.39772594534997],[-87.62422814978432,41.39772737299857],[-87.62421774548025,41.39772805659901],[-87.62420730201784,41.39772798991927],[-87.62419691460487,41.3977271735672],[-87.62418667793823,41.3977256149851],[-87.62418671102395,41.3977256212699],[-87.62407665709884,41.39770472967701],[-87.62406629597992,41.397702346179805],[-87.62405629881992,41.397699202590374],[-87.62405211939647,41.3976975050517],[-87.62403011344777,41.397692436957406],[-87.62402019045922,41.39769240856049],[-87.62400961007666,41.39769160064994],[-87.6239991838944,41.39769002289897],[-87.62394034597573,41.397678853666775],[-87.62392998485687,41.397676470172],[-87.6239199876966,41.39767332658449],[-87.62391045256837,41.39766945374326],[-87.62390147301304,41.3976648896414],[-87.62389709425379,41.39766215257271],[-87.62389409652785,41.397661423260395],[-87.6238838004308,41.39765847960019],[-87.62387394964163,41.3976547712504],[-87.62386464402535,41.397650335805466],[-87.62385597792006,41.3976452182309],[-87.62384803918056,41.397639470407476],[-87.62384090828776,41.3976331506053],[-87.623839286541,41.39763137916821],[-87.62383675849487,41.397629285732634],[-87.62383035228544,41.397622804159624],[-87.62382482029217,41.39761588114358],[-87.62382021574966,41.397608583305356],[-87.62381658296758,41.39760098087273],[-87.62381395690413,41.39759314700461],[-87.62381236282981,41.39758515708701],[-87.62381181608414,41.397577088007544],[-87.62381232192811,41.39756901741562],[-87.6238138754936,41.39756102297521],[-87.62381646183007,41.39755318161735],[-87.62386309049305,41.397436588717746],[-87.62386670290655,41.39742894262843],[-87.62387129711452,41.39742160135193],[-87.62387682851207,41.39741463616366],[-87.6238832433953,41.39740811468775],[-87.62389047948277,41.39740210024026],[-87.62389846652009,41.397396651214606],[-87.6239071269621,41.39739182051462],[-87.62391637672572,41.39738765504086],[-87.6239261260062,41.39738419523529],[-87.62393628014925,41.3973814746886],[-87.62394674056974,41.397379519814216],[-87.62395740570904,41.39737834959169],[-87.62396817202092,41.397377975382526],[-87.62397893497695,41.397378400819846],[-87.62398959008122,41.3973796217732],[-87.62400003388497,41.39738162638845],[-87.62400459928844,41.397382685573255],[-87.6240097418674,41.39738137496058],[-87.62401988537127,41.39737957809739],[-87.62403020992313,41.39737851619985],[-87.6240406218205,41.39737819890541],[-87.62405102656818,41.39737862909373],[-87.62406132973588,41.39737980286054],[-87.62407143781516,41.39738170955312],[-87.62416781499175,41.397403611535694],[-87.62422983409283,41.39741559488651],[-87.62424038602445,41.3974180677156],[-87.62425055272993,41.397421329650655],[-87.62426023043129,41.39742534739508],[-87.62426932034207,41.39743007993722],[-87.62427772967571,41.39743547896907],[-87.6242853725927,41.397441489379304],[-87.62429217107669,41.397448049815836],[-87.62429313249845,41.397449200566754],[-87.6242938761274,41.39744938185984]]]}`)
	require.NoError(t, inner.Validate())

	outer := mustGeoJSON(t, `{"type":"Polygon","coordinates":[[[-87.62444917095299,41.39729331748811],[-87.62446704222914,41.397301659153754],[-87.62449506935019,41.39731775684101],[-87.62452090105552,41.397335817239],[-87.62454429589731,41.39735567153923],[-87.6245650352042,41.3973771341657],[-87.6245829251253,41.397400004509386],[-87.62459779844208,41.397424068803204],[-87.62460951613143,41.397449102120135],[-87.62461796866529,41.39747487047549],[-87.6246230770344,41.39750113301402],[-87.62462479348707,41.39752764426096],[-87.6246231019755,41.39755415641672],[-87.62461801830612,41.397580421672856],[-87.62460958999183,41.39760619452835],[-87.62456285356899,41.397724210992784],[-87.62455132416264,41.39774894508767],[-87.62453671452448,41.3977727384771],[-87.62451915784027,41.397795374248304],[-87.62449881416285,41.39781664604174],[-87.62447586895344,41.39783635993238],[-87.62445053139074,41.39785433619775],[-87.62442303246401,41.397870410956294],[-87.62439362286723,41.39788443766158],[-87.62436257071374,41.39789628843825],[-87.62433015909178,41.39790585524787],[-87.62429668348378,41.3979130508739],[-87.62426244907233,41.39791780971686],[-87.62422776795812,41.397920088392326],[-87.62419295631425,41.397919866126564],[-87.62415833150395,41.39791714494585],[-87.62412420918706,41.397911949658024],[-87.62412431963479,41.397911970638134],[-87.6240142654138,41.3978910789883],[-87.62397972826206,41.397883133976144],[-87.62397604150179,41.39788197468104],[-87.62397154652997,41.39788163144765],[-87.62393679249253,41.397876372263475],[-87.6238779544157,41.39786520300083],[-87.62384341726417,41.3978572579968],[-87.6238100933212,41.39784677934415],[-87.62377830950128,41.397833869840746],[-87.62377439835728,41.39783188189482],[-87.62374847092677,41.39782212145373],[-87.62371745215871,41.397807336601254],[-87.62368856511434,41.397790277980455],[-87.62366210264413,41.397771118528894],[-87.62364238065591,41.39775363973907],[-87.62363973273321,41.3977514470298],[-87.62363850541901,41.39775020527393],[-87.62363833301796,41.39775005248186],[-87.62363806435583,41.39774975902078],[-87.6236183787311,41.3977298417487],[-87.62359993880196,41.397706764993615],[-87.62358459039267,41.39768243883536],[-87.62357248119949,41.39765709736778],[-87.62356372774683,41.3976309844548],[-87.62355841426607,41.39760435138386],[-87.62355659188512,41.3975774544476],[-87.62355827813658,41.39755055247751],[-87.62356345678923,41.39752390435329],[-87.62357207800432,41.39749776651146],[-87.6236187070669,41.39738117370699],[-87.62363074852786,41.397355686766915],[-87.62364606262244,41.39733121587506],[-87.62366450066513,41.39730799861518],[-87.62368588364099,41.39728626039952],[-87.62371000394393,41.3972662122803],[-87.62373662739223,41.397248048900735],[-87.62376549550245,41.39723194660534],[-87.62379632799865,41.3972180617278],[-87.62382882553379,41.39720652907334],[-87.62386267259592,41.397197460609846],[-87.62389754057125,41.397190944380924],[-87.62393309093454,41.39718704365108],[-87.62396897853569,41.39718579629156],[-87.62400485495054,41.39718721441263],[-87.62400561478837,41.397187301481495],[-87.62400775375312,41.39718708148513],[-87.6240424599759,41.39718602384076],[-87.6240771423665,41.39718745779836],[-87.62411148616091,41.39719137034386],[-87.62414517966795,41.39719772596847],[-87.62423643421413,41.3972184638187],[-87.6242932704773,41.39722944573794],[-87.62432844349291,41.39723768847929],[-87.62436233243534,41.39724856156757],[-87.62439459138113,41.397261954015285],[-87.62442489104455,41.39727772911831],[-87.62444917095299,41.39729331748811]]]}`)
	require.NoError(t, outer.Validate())

	diffGeom, err := geom.Difference(outer, inner)
	require.NoError(t, err)

	require.NoError(t, diffGeom.Validate())
	b, err := diffGeom.MarshalJSON()
	require.NoError(t, err)
	fmt.Println(string(b))
}

func mustGeoJSON(t *testing.T, geojson string) geom.Geometry {
	var g geom.Geometry
	err := json.NewDecoder(strings.NewReader(geojson)).Decode(&g)
	require.NoError(t, err)
	return g
}

Expected:

Expecting a geometry of the difference of the two polygons above with no error.