getting rid of the unsupported 'github.com/ipfs/go-ipfs-api' package and replacing it with an equivalent interface

go.mod

@@ -6,7 +6,6 @@ require (
 	github.com/iden3/go-iden3-core/v2 v2.0.3
 	github.com/iden3/go-iden3-crypto v0.0.15
 	github.com/iden3/go-merkletree-sql/v2 v2.0.4
-	github.com/ipfs/go-ipfs-api v0.7.0
 	// We require the `json-gold` bugfix which has not yet been included in the
 	// stable version. After the release of version 0.5.1 or later, it will be
 	// necessary to update to the stable version.
@@ -20,33 +19,10 @@ require (
 )
 
 require (
-	github.com/benbjohnson/clock v1.3.5 // indirect
-	github.com/blang/semver/v4 v4.0.0 // indirect
-	github.com/crackcomm/go-gitignore v0.0.0-20170627025303-887ab5e44cc3 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dchest/blake512 v1.0.0 // indirect
-	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.2.0 // indirect
-	github.com/ipfs/boxo v0.12.0 // indirect
-	github.com/ipfs/go-cid v0.4.1 // indirect
-	github.com/klauspost/cpuid/v2 v2.2.5 // indirect
-	github.com/libp2p/go-buffer-pool v0.1.0 // indirect
-	github.com/libp2p/go-flow-metrics v0.1.0 // indirect
-	github.com/libp2p/go-libp2p v0.26.3 // indirect
-	github.com/minio/sha256-simd v1.0.1 // indirect
-	github.com/mitchellh/go-homedir v1.1.0 // indirect
 	github.com/mr-tron/base58 v1.2.0 // indirect
-	github.com/multiformats/go-base32 v0.1.0 // indirect
-	github.com/multiformats/go-base36 v0.2.0 // indirect
-	github.com/multiformats/go-multiaddr v0.9.0 // indirect
-	github.com/multiformats/go-multibase v0.2.0 // indirect
-	github.com/multiformats/go-multicodec v0.9.0 // indirect
-	github.com/multiformats/go-multihash v0.2.3 // indirect
-	github.com/multiformats/go-multistream v0.4.1 // indirect
-	github.com/multiformats/go-varint v0.0.7 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/spaolacci/murmur3 v1.1.0 // indirect
 	golang.org/x/sys v0.8.0 // indirect
-	google.golang.org/protobuf v1.30.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
-	lukechampine.com/blake3 v1.2.1 // indirect
 )

go.sum

@@ -1,63 +1,16 @@
-github.com/benbjohnson/clock v1.3.5 h1:VvXlSJBzZpA/zum6Sj74hxwYI2DIxRWuNIoXAzHZz5o=
-github.com/benbjohnson/clock v1.3.5/go.mod h1:J11/hYXuz8f4ySSvYwY0FKfm+ezbsZBKZxNJlLklBHA=
-github.com/blang/semver/v4 v4.0.0 h1:1PFHFE6yCCTv8C1TeyNNarDzntLi7wMI5i/pzqYIsAM=
-github.com/blang/semver/v4 v4.0.0/go.mod h1:IbckMUScFkM3pff0VJDNKRiT6TG/YpiHIM2yvyW5YoQ=
-github.com/cheekybits/is v0.0.0-20150225183255-68e9c0620927 h1:SKI1/fuSdodxmNNyVBR8d7X/HuLnRpvvFO0AgyQk764=
-github.com/crackcomm/go-gitignore v0.0.0-20170627025303-887ab5e44cc3 h1:HVTnpeuvF6Owjd5mniCL8DEXo7uYXdQEmOP4FJbV5tg=
-github.com/crackcomm/go-gitignore v0.0.0-20170627025303-887ab5e44cc3/go.mod h1:p1d6YEZWvFzEh4KLyvBcVSnrfNDDvK2zfK/4x2v/4pE=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dchest/blake512 v1.0.0 h1:oDFEQFIqFSeuA34xLtXZ/rWxCXdSjirjzPhey5EUvmA=
 github.com/dchest/blake512 v1.0.0/go.mod h1:FV1x7xPPLWukZlpDpWQ88rF/SFwZ5qbskrzhLMB92JI=
-github.com/decred/dcrd/crypto/blake256 v1.0.1 h1:7PltbUIQB7u/FfZ39+DGa/ShuMyJ5ilcvdfma9wOH6Y=
-github.com/decred/dcrd/dcrec/secp256k1/v4 v4.2.0 h1:8UrgZ3GkP4i/CLijOJx79Yu+etlyjdBU4sfcs2WYQMs=
-github.com/decred/dcrd/dcrec/secp256k1/v4 v4.2.0/go.mod h1:v57UDF4pDQJcEfFUCRop3lJL149eHGSe9Jvczhzjo/0=
-github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
-github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
-github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/iden3/go-iden3-core/v2 v2.0.3 h1:ce9Jbw10zDsinWXFc05SiK2Hof/wu4zV4/ai5gQy29k=
 github.com/iden3/go-iden3-core/v2 v2.0.3/go.mod h1:L9PxhWPvoS9qTb3inEkZBm1RpjHBt+VTwvxssdzbAdw=
 github.com/iden3/go-iden3-crypto v0.0.15 h1:4MJYlrot1l31Fzlo2sF56u7EVFeHHJkxGXXZCtESgK4=
 github.com/iden3/go-iden3-crypto v0.0.15/go.mod h1:dLpM4vEPJ3nDHzhWFXDjzkn1qHoBeOT/3UEhXsEsP3E=
 github.com/iden3/go-merkletree-sql/v2 v2.0.4 h1:Dp089P3YNX1BE8+T1tKQHWTtnk84Y/Kr7ZAGTqwscoY=
 github.com/iden3/go-merkletree-sql/v2 v2.0.4/go.mod h1:kRhHKYpui5DUsry5RpveP6IC4XMe6iApdV9VChRYuEk=
-github.com/ipfs/boxo v0.12.0 h1:AXHg/1ONZdRQHQLgG5JHsSC3XoE4DjCAMgK+asZvUcQ=
-github.com/ipfs/boxo v0.12.0/go.mod h1:xAnfiU6PtxWCnRqu7dcXQ10bB5/kvI1kXRotuGqGBhg=
-github.com/ipfs/go-cid v0.4.1 h1:A/T3qGvxi4kpKWWcPC/PgbvDA2bjVLO7n4UeVwnbs/s=
-github.com/ipfs/go-cid v0.4.1/go.mod h1:uQHwDeX4c6CtyrFwdqyhpNcxVewur1M7l7fNU7LKwZk=
-github.com/ipfs/go-ipfs-api v0.7.0 h1:CMBNCUl0b45coC+lQCXEVpMhwoqjiaCwUIrM+coYW2Q=
-github.com/ipfs/go-ipfs-api v0.7.0/go.mod h1:AIxsTNB0+ZhkqIfTZpdZ0VR/cpX5zrXjATa3prSay3g=
-github.com/klauspost/cpuid/v2 v2.2.5 h1:0E5MSMDEoAulmXNFquVs//DdoomxaoTY1kUhbc/qbZg=
-github.com/klauspost/cpuid/v2 v2.2.5/go.mod h1:Lcz8mBdAVJIBVzewtcLocK12l3Y+JytZYpaMropDUws=
 github.com/leanovate/gopter v0.2.9 h1:fQjYxZaynp97ozCzfOyOuAGOU4aU/z37zf/tOujFk7c=
-github.com/libp2p/go-buffer-pool v0.1.0 h1:oK4mSFcQz7cTQIfqbe4MIj9gLW+mnanjyFtc6cdF0Y8=
-github.com/libp2p/go-buffer-pool v0.1.0/go.mod h1:N+vh8gMqimBzdKkSMVuydVDq+UV5QTWy5HSiZacSbPg=
-github.com/libp2p/go-flow-metrics v0.1.0 h1:0iPhMI8PskQwzh57jB9WxIuIOQ0r+15PChFGkx3Q3WM=
-github.com/libp2p/go-flow-metrics v0.1.0/go.mod h1:4Xi8MX8wj5aWNDAZttg6UPmc0ZrnFNsMtpsYUClFtro=
-github.com/libp2p/go-libp2p v0.26.3 h1:6g/psubqwdaBqNNoidbRKSTBEYgaOuKBhHl8Q5tO+PM=
-github.com/libp2p/go-libp2p v0.26.3/go.mod h1:x75BN32YbwuY0Awm2Uix4d4KOz+/4piInkp4Wr3yOo8=
-github.com/minio/sha256-simd v1.0.1 h1:6kaan5IFmwTNynnKKpDHe6FWHohJOHhCPchzK49dzMM=
-github.com/minio/sha256-simd v1.0.1/go.mod h1:Pz6AKMiUdngCLpeTL/RJY1M9rUuPMYujV5xJjtbRSN8=
-github.com/mitchellh/go-homedir v1.1.0 h1:lukF9ziXFxDFPkA1vsr5zpc1XuPDn/wFntq5mG+4E0Y=
-github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
 github.com/mr-tron/base58 v1.2.0 h1:T/HDJBh4ZCPbU39/+c3rRvE0uKBQlU27+QI8LJ4t64o=
 github.com/mr-tron/base58 v1.2.0/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjWI2mNwc=
-github.com/multiformats/go-base32 v0.1.0 h1:pVx9xoSPqEIQG8o+UbAe7DNi51oej1NtK+aGkbLYxPE=
-github.com/multiformats/go-base32 v0.1.0/go.mod h1:Kj3tFY6zNr+ABYMqeUNeGvkIC/UYgtWibDcT0rExnbI=
-github.com/multiformats/go-base36 v0.2.0 h1:lFsAbNOGeKtuKozrtBsAkSVhv1p9D0/qedU9rQyccr0=
-github.com/multiformats/go-base36 v0.2.0/go.mod h1:qvnKE++v+2MWCfePClUEjE78Z7P2a1UV0xHgWc0hkp4=
-github.com/multiformats/go-multiaddr v0.9.0 h1:3h4V1LHIk5w4hJHekMKWALPXErDfz/sggzwC/NcqbDQ=
-github.com/multiformats/go-multiaddr v0.9.0/go.mod h1:mI67Lb1EeTOYb8GQfL/7wpIZwc46ElrvzhYnoJOmTT0=
-github.com/multiformats/go-multibase v0.2.0 h1:isdYCVLvksgWlMW9OZRYJEa9pZETFivncJHmHnnd87g=
-github.com/multiformats/go-multibase v0.2.0/go.mod h1:bFBZX4lKCA/2lyOFSAoKH5SS6oPyjtnzK/XTFDPkNuk=
-github.com/multiformats/go-multicodec v0.9.0 h1:pb/dlPnzee/Sxv/j4PmkDRxCOi3hXTz3IbPKOXWJkmg=
-github.com/multiformats/go-multicodec v0.9.0/go.mod h1:L3QTQvMIaVBkXOXXtVmYE+LI16i14xuaojr/H7Ai54k=
-github.com/multiformats/go-multihash v0.2.3 h1:7Lyc8XfX/IY2jWb/gI7JP+o7JEq9hOa7BFvVU9RSh+U=
-github.com/multiformats/go-multihash v0.2.3/go.mod h1:dXgKXCXjBzdscBLk9JkjINiEsCKRVch90MdaGiKsvSM=
-github.com/multiformats/go-multistream v0.4.1 h1:rFy0Iiyn3YT0asivDUIR05leAdwZq3de4741sbiSdfo=
-github.com/multiformats/go-multistream v0.4.1/go.mod h1:Mz5eykRVAjJWckE2U78c6xqdtyNUEhKSM0Lwar2p77Q=
-github.com/multiformats/go-varint v0.0.7 h1:sWSGR+f/eu5ABZA2ZpYKBILXTTs9JWpdEM/nEGOHFS8=
-github.com/multiformats/go-varint v0.0.7/go.mod h1:r8PUYw/fD/SjBCiKOoDlGF6QawOELpZAu9eioSos/OU=
 github.com/piprate/json-gold v0.5.1-0.20230111113000-6ddbe6e6f19f h1:HlPa7RcxTCrva5izPfTEfvYecO7LTahgmMRD1Qp13xg=
 github.com/piprate/json-gold v0.5.1-0.20230111113000-6ddbe6e6f19f/go.mod h1:WZ501QQMbZZ+3pXFPhQKzNwS1+jls0oqov3uQ2WasLs=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
@@ -68,23 +21,13 @@ github.com/pquerna/cachecontrol v0.0.0-20180517163645-1555304b9b35 h1:J9b7z+QKAm
 github.com/pquerna/cachecontrol v0.0.0-20180517163645-1555304b9b35/go.mod h1:prYjPmNq4d1NPVmpShWobRqXY3q7Vp+80DqgxxUrUIA=
 github.com/santhosh-tekuri/jsonschema/v5 v5.3.0 h1:uIkTLo0AGRc8l7h5l9r+GcYi9qfVPt6lD4/bhmzfiKo=
 github.com/santhosh-tekuri/jsonschema/v5 v5.3.0/go.mod h1:FKdcjfQW6rpZSnxxUvEA5H/cDPdvJ/SZJQLWWXWGrZ0=
-github.com/spaolacci/murmur3 v1.1.0 h1:7c1g84S4BPRrfL5Xrdp6fOJ206sU9y293DDHaoy0bLI=
-github.com/spaolacci/murmur3 v1.1.0/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 golang.org/x/crypto v0.7.0 h1:AvwMYaRytfdeVt3u6mLaxYtErKYjxA2OXjJ1HHq6t3A=
 golang.org/x/crypto v0.7.0/go.mod h1:pYwdfH91IfpZVANVyUOhSIPZaFoJGxTFbZhFTx+dXZU=
-golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.8.0 h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=
 golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 h1:H2TDz8ibqkAF6YGhCdN3jS9O0/s90v0rJh3X/OLHEUk=
-google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
-google.golang.org/protobuf v1.30.0 h1:kPPoIgf3TsEvrm0PFe15JQ+570QVxYzEvvHqChK+cng=
-google.golang.org/protobuf v1.30.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-lukechampine.com/blake3 v1.2.1 h1:YuqqRuaqsGV71BV/nm9xlI0MKUv4QC54jQnBChWbGnI=
-lukechampine.com/blake3 v1.2.1/go.mod h1:0OFRp7fBtAylGVCO40o87sbupkyIGgbpv1+M1k1LM6k=

loaders/document_loader.go

@@ -9,7 +9,6 @@ import (
 	"strings"
 	"time"
 
-	shell "github.com/ipfs/go-ipfs-api"
 	"github.com/piprate/json-gold/ld"
 	"github.com/pquerna/cachecontrol"
 )
@@ -31,8 +30,12 @@ type CacheEngine interface {
 	Set(key string, doc *ld.RemoteDocument, expireTime time.Time) error
 }
 
+type IPFSClient interface {
+	Cat(url string) (io.ReadCloser, error)
+}
+
 type documentLoader struct {
-	ipfsCli     *shell.Shell
+	ipfsCli     IPFSClient // @formatter:off : Goland bug
 	ipfsGW      string
 	cacheEngine CacheEngine
 	noCache     bool
@@ -60,7 +63,7 @@ func WithHTTPClient(httpClient *http.Client) DocumentLoaderOption {
 
 // NewDocumentLoader creates a new document loader with a cache for http.
 // ipfs cache is not implemented yet.
-func NewDocumentLoader(ipfsCli *shell.Shell, ipfsGW string,
+func NewDocumentLoader(ipfsCli IPFSClient, ipfsGW string,
 	opts ...DocumentLoaderOption) ld.DocumentLoader {
 	loader := &documentLoader{
 		ipfsCli: ipfsCli,

merklize/merklize.go

@@ -18,7 +18,6 @@ import (
 	"github.com/iden3/go-merkletree-sql/v2"
 	"github.com/iden3/go-merkletree-sql/v2/db/memory"
 	"github.com/iden3/go-schema-processor/v2/loaders"
-	shell "github.com/ipfs/go-ipfs-api"
 	"github.com/piprate/json-gold/ld"
 )
 
@@ -1462,7 +1461,7 @@ type Merklizer struct {
 	entries        map[string]RDFEntry
 	hasher         Hasher
 	safeMode       bool
-	ipfsCli        *shell.Shell
+	ipfsCli        loaders.IPFSClient // @formatter:off : Goland bug
 	ipfsGW         string
 	documentLoader ld.DocumentLoader
 }
@@ -1498,7 +1497,7 @@ func WithSafeMode(safeMode bool) MerklizeOption {
 // WithIPFSClient sets IPFS client option required to resolve ipfs:// contexts.
 // It works only if documentLoader is not set using WithDocumentLoader option.
 // Otherwise, it will be ignored.
-func WithIPFSClient(ipfsCli *shell.Shell) MerklizeOption {
+func WithIPFSClient(ipfsCli loaders.IPFSClient) MerklizeOption {
 	return func(m *Merklizer) {
 		m.ipfsCli = ipfsCli
 	}

merklize/merklize_test.go

@@ -4,7 +4,9 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"io"
 	"math"
 	"math/big"
 	"os"
@@ -21,7 +23,6 @@ import (
 	"github.com/iden3/go-merkletree-sql/v2/db/memory"
 	"github.com/iden3/go-schema-processor/v2/loaders"
 	tst "github.com/iden3/go-schema-processor/v2/testing"
-	shell "github.com/ipfs/go-ipfs-api"
 	"github.com/piprate/json-gold/ld"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -1888,7 +1889,7 @@ const ipfsDocument = `{
   "@context": [
     "https://www.w3.org/2018/credentials/v1",
     "{{ .CitizenshipContext }}",
-	"{{ .BBSContext }}"
+    "{{ .BBSContext }}"
   ],
   "id": "https://issuer.oidp.uscis.gov/credentials/83627465",
   "type": ["VerifiableCredential", "PermanentResidentCard"],
@@ -1930,50 +1931,38 @@ const ipfsDocument = `{
   ]
 }`
 
-func uploadIPFSFile(t testing.TB, ipfsCli *shell.Shell, fName string) string {
-	f, err := os.Open(fName)
-	require.NoError(t, err)
-	// no need to close f
-
-	// Context is a pure file (no directory)
-	cid, err := ipfsCli.Add(f)
-	require.NoError(t, err)
+type mockIPFSLoader map[string]string
 
-	return cid
+func (m mockIPFSLoader) Cat(url string) (io.ReadCloser, error) {
+	fName, ok := m[url]
+	if !ok {
+		return nil, errors.New("not found")
+	}
+	return os.Open(fName)
 }
 
 func TestIPFSContext(t *testing.T) {
-	ipfsURL := os.Getenv("IPFS_URL")
-	if ipfsURL == "" {
-		t.Skip("IPFS_URL is not set")
-	}
+
+	bbsCtx := "Qmbp4kwoHULnmK71abrxdksjPH5sAjxSAXU5PEp2XRMFNw/dir2/bbs-v2.jsonld"
+	citizenshipCtx := "QmdP4MZkESEabRVB322r2xWm7TCi7LueMNWMJawYmSy7hp"
 
 	defer tst.MockHTTPClient(t, testDocumentIPFSURLMaps,
 		tst.IgnoreUntouchedURLs())()
 
-	ipfsCli := shell.NewShell(ipfsURL)
-
-	// Context inside some directory
-	bbsCtx, err := ipfsCli.AddDir("testdata/ipfs/dir1")
-	require.NoError(t, err)
-	bbsCtx = "ipfs://" + bbsCtx + "/dir2/bbs-v2.jsonld"
-
-	citizenshipCtx := uploadIPFSFile(t, ipfsCli,
-		"testdata/ipfs/citizenship-v1.jsonld")
-	citizenshipCtx = "ipfs://" + citizenshipCtx
+	ipfsCli := mockIPFSLoader{
+		bbsCtx:         "testdata/ipfs/dir1/dir2/bbs-v2.jsonld",
+		citizenshipCtx: "testdata/ipfs/citizenship-v1.jsonld",
+		"QmeMevwUeD7o6hjfmdaeFD1q4L84hSDiRjeXZLi1bZK1My": "testdata/ipfs/testNewType.jsonld",
+	}
 
 	tmpl := template.Must(template.New("").Parse(ipfsDocument))
 	b := bytes.NewBuffer(nil)
-	err = tmpl.Execute(b, map[string]interface{}{
-		"CitizenshipContext": citizenshipCtx,
-		"BBSContext":         bbsCtx,
+	err := tmpl.Execute(b, map[string]interface{}{
+		"CitizenshipContext": "ipfs://" + citizenshipCtx,
+		"BBSContext":         "ipfs://" + bbsCtx,
 	})
 	require.NoError(t, err)
 
-	cid := uploadIPFSFile(t, ipfsCli, "testdata/ipfs/testNewType.jsonld")
-	// CID should be equal to the on in `testDocumentIPFS` document
-	require.Equal(t, "QmeMevwUeD7o6hjfmdaeFD1q4L84hSDiRjeXZLi1bZK1My", cid)
-
 	ctx, cancel := context.WithTimeout(context.Background(), time.Second*30)
 	defer cancel()