Closed ainar-g closed 5 months ago
We'd be happy to accept a CL--if you think it should be off by default, we can start with that first, and then enable it later on?
Ah, looks like it uses SSA, so let's keep it off by default to start.
Change https://golang.org/cl/295172 mentions this issue: internal/lsp/source: add the unusedwrite analyzer
Thanks for reviewing!
SSA is now enabled by default (for nilness), so the marginal cost of enabling unusedwrite is very small. I just ran a very quick experiment and found that 10 out of 10 findings I randomly sampled in kubernetes were genuine opportunities for simplification. So let's do a proper evaluation and perhaps enable it in gopls.
I should run a job over the Module Mirror corpus to get results that we can share, but in the meantime Googlers can inspect a list of findings of this analyzer on Google source code at go/unusedwrite-diagnostics-b1c6ea0fd8b46c. The false positive rate is zero in my manual sampling so far. I think this might be a good feature for gopls.
I ran unusedwrite over the Module Mirror corpus of 22867 modules. It reported 2976 unique diagnostics, of which 100 picked at random are shown below. I analyzed a dozen or so by hand, and all were true positives, indicating that the code was unnecessarily complicated and confusing, though potentially still correct; but in three cases, the excessive complexity was clear evidence of a bug, for example updating a field of the receiver struct before returning from a method with a non-pointer receiver.
I think we should enable this analyzer by default in gopls.
The complete list is here: unusedwrite.txt
https://go-mod-viewer.appspot.com/github.com/shuguocloud/go-zero@v1.3.0/rest/httpx/requests_test.go#L312: unused write to field Percent https://go-mod-viewer.appspot.com/github.com/o1egl/govatar@v0.4.1/govatar_test.go#L182: unused write to field B https://go-mod-viewer.appspot.com/github.com/yitter/idgenerator-go@v1.3.3/idgen/OverCostActionArg.go#L25: unused write to field TermIndex https://go-mod-viewer.appspot.com/github.com/ergo-services/ergo@v1.999.224/etf/decode.go#L1171: unused write to field Module https://go-mod-viewer.appspot.com/github.com/estesp/manifest-tool@v1.0.3/docker/inspect_v2.go#L66: unused write to field MediaType https://go-mod-viewer.appspot.com/github.com/datachainlab/cross@v0.2.2/x/packets/types.go#L250: unused write to field payload https://go-mod-viewer.appspot.com/github.com/takumakei/go-urfave-cli/clix@v0.0.0-20210528051825-f43cf228bf5d/filepath_test.go#L25: unused write to field FilePath https://go-mod-viewer.appspot.com/github.com/abadojack/whatlanggo@v1.0.1/detect_test.go#L82: unused write to field Confidence https://go-mod-viewer.appspot.com/github.com/nacos-group/nacos-sdk-go/v2@v2.2.5/clients/naming_client/naming_cache/subscribe_callback_test.go#L77: unused write to field LastRefTime https://go-mod-viewer.appspot.com/github.com/perimeterx/marshmallow@v1.1.5/unmarshal_test.go#L1231: unused write to field ChildField26 https://go-mod-viewer.appspot.com/github.com/selefra/selefra-provider-sdk@v0.0.23/provider/transformer/column_value_extractor/examples/column_value_extractor_wrapper/main.go#L15: unused write to field TableName https://go-mod-viewer.appspot.com/github.com/DoNewsCode/core@v0.12.3/codec/yaml/yaml_test.go#L88: unused write to field A https://go-mod-viewer.appspot.com/github.com/adharshmk96/stk@v1.2.3/pkg/sqlMigrator/generator_test.go#L97: unused write to field Name https://go-mod-viewer.appspot.com/github.com/laher/argo@v0.0.0-20140722103944-11d91c83cc0f/ar/reader_test.go#L293: unused write to field closed https://go-mod-viewer.appspot.com/github.com/argoproj/argo-cd/v2@v2.10.5/util/db/repository_legacy.go#L285: unused write to field GithubAppInstallationId https://go-mod-viewer.appspot.com/github.com/ti-mo/conntrack@v0.5.0/attribute_types_test.go#L297: unused write to field Type https://go-mod-viewer.appspot.com/github.com/n0madic/twitter-scraper@v0.0.0-20231104223941-296710769dd8/tweets_test.go#L279: unused write to field Name https://go-mod-viewer.appspot.com/github.com/dolthub/go-mysql-server@v0.18.0/sql/expression/function/string_test.go#L146: unused write to field Name https://go-mod-viewer.appspot.com/gopkg.in/goose.v2@v2.0.1/testservices/novaservice/service_http_test.go#L1314: unused write to field Addresses https://go-mod-viewer.appspot.com/github.com/drone/go-convert@v0.0.0-20240307072510-6bd371c65e61/convert/circle/convert.go#L132: unused write to field Inputs https://go-mod-viewer.appspot.com/github.com/smartwalle/ncrypto@v1.0.4/pkcs12/pkcs12_test.go#L83: unused write to field Certificates https://go-mod-viewer.appspot.com/github.com/unidoc/unidoc@v2.2.0+incompatible/pdf/model/fonts/helvetica_bold_oblique.go#L30: unused write to field encoder https://go-mod-viewer.appspot.com/github.com/projecteru2/core@v0.0.0-20240321043226-06bcc1c23f58/cluster/calcium/wal_test.go#L134: unused write to field Engine https://go-mod-viewer.appspot.com/github.com/ethereum-optimism/optimism@v1.7.2/op-node/rollup/derive/batches_test.go#L191: unused write to field Hash https://go-mod-viewer.appspot.com/github.com/stafiprotocol/go-substrate-rpc-client@v1.4.7/types/multi_address.go#L111: unused write to field IsAddress32 https://go-mod-viewer.appspot.com/github.com/whatap/golib@v0.0.22/util/hmap/IntSet.go#L205: unused write to field table https://go-mod-viewer.appspot.com/github.com/siglens/siglens@v0.0.0-20240328180423-f7ce9ae441ed/pkg/integrations/loki/loki.go#L553: unused write to field ExecTime https://go-mod-viewer.appspot.com/github.com/minio/minio@v0.0.0-20240328213742-3f72439b8a27/cmd/erasure-multipart.go#L871: unused write to field MaxSize https://go-mod-viewer.appspot.com/github.com/hashicorp/cap@v0.6.0/oidc/options_test.go#L34: unused write to field withNowFunc https://go-mod-viewer.appspot.com/github.com/gocrane/crane@v0.11.0/pkg/utils/expression_prom_deafult_test.go#L163: unused write to field description https://go-mod-viewer.appspot.com/github.com/pion/rtp@v1.8.5/packet_test.go#L901: unused write to field Payload https://go-mod-viewer.appspot.com/github.com/ti-mo/conntrack@v0.5.0/attribute_types_test.go#L269: unused write to field Type https://go-mod-viewer.appspot.com/github.com/ardanlabs/conf/v2@v2.2.0/conf_test.go#L495: unused write to field name https://go-mod-viewer.appspot.com/github.com/perimeterx/marshmallow@v1.1.5/unmarshal_from_json_map_test.go#L907: unused write to field ChildField6 https://go-mod-viewer.appspot.com/github.com/nntaoli-project/goex@v1.3.3/okex/OKExSwap.go#L457: unused write to field InstrumentId https://go-mod-viewer.appspot.com/github.com/ti-mo/conntrack@v0.5.0/attribute_types_test.go#L234: unused write to field Nested https://go-mod-viewer.appspot.com/github.com/google/battery-historian@v0.0.0-20170519220231-d2356ba4fd5f/checkindelta/checkin_normalize.go#L49: unused write to field AggregationType https://go-mod-viewer.appspot.com/github.com/hellobchain/newcryptosm@v0.0.0-20221019060107-edb949a317e9/sm9/sm9_test.go#L523: unused write to field t https://go-mod-viewer.appspot.com/github.com/akamai/AkamaiOPEN-edgegrid-golang@v1.2.2/configgtm-v1_5/errors.go#L39: unused write to field err https://go-mod-viewer.appspot.com/github.com/nntaoli-project/goex@v1.3.3/binance/SpotWs.go#L227: unused write to field Amount https://go-mod-viewer.appspot.com/github.com/kyma-project/kyma-environment-broker@v0.0.1/internal/provisioner/client_test.go#L417: unused write to field RuntimeID https://go-mod-viewer.appspot.com/github.com/pingcap/tiflow@v0.0.0-20240329071719-db60e9e8de74/cdc/scheduler/internal/v3/keyspan/splitter_region_count_test.go#L194: unused write to field EnableTableAcrossNodes https://go-mod-viewer.appspot.com/github.com/aacfactory/fns-contrib/databases/sql@v1.2.84/rows.go#L660: unused write to field size https://go-mod-viewer.appspot.com/github.com/huaweicloud/golangsdk@v0.0.0-20210831081626-d823fe11ceba/openstack/dns/v2/recordsets/testing/requests_test.go#L140: unused write to field Version https://go-mod-viewer.appspot.com/cloud.google.com/go/storage@v1.40.0/client_test.go#L336: unused write to field Bucket https://go-mod-viewer.appspot.com/gopkg.in/httprequest.v1@v1.2.1/bench_test.go#L425: unused write to field Field5 https://go-mod-viewer.appspot.com/github.com/alibaba/sentinel-golang@v1.0.4/core/stat/base/leap_array_test.go#L39: unused write to field BucketStart https://go-mod-viewer.appspot.com/github.com/cozy/cozy-stack@v0.0.0-20240327093429-939e4a21320e/model/move/cursor.go#L127: unused write to field Number https://go-mod-viewer.appspot.com/github.com/gonum/lapack@v0.0.0-20181123203213-e4cdc5a0bff9/testlapack/dgetrs.go#L102: unused write to field Cols https://go-mod-viewer.appspot.com/github.com/yitter/idgenerator-go@v1.3.3/idgen/OverCostActionArg.go#L24: unused write to field GenCountInOneTerm https://go-mod-viewer.appspot.com/github.com/quic-go/quic-go@v0.42.0/internal/wire/ack_frame.go#L259: unused write to field Smallest https://go-mod-viewer.appspot.com/github.com/laher/uggo@v0.0.0-20140418102112-0ad25fe11c5b/flagsetaliasedvars.go#L91: unused write to field out https://go-mod-viewer.appspot.com/github.com/mattermost/mattermost-plugin-api@v0.1.4/i18n/i18n_test.go#L32: unused write to field b https://go-mod-viewer.appspot.com/github.com/nacos-group/nacos-sdk-go@v1.1.4/clients/naming_client/subscribe_callback_test.go#L78: unused write to field LastRefTime https://go-mod-viewer.appspot.com/k8s.io/apiserver@v0.29.3/pkg/storage/value/encrypt/envelope/metrics/metrics_test.go#L345: unused write to field apiServerIDHash https://go-mod-viewer.appspot.com/github.com/zondax/ledger-go@v0.14.3/apduWrapper_test.go#L117: unused write to field tag https://go-mod-viewer.appspot.com/github.com/hduhelp/go-zero@v1.4.3/gateway/server.go#L172: unused write to field Name https://go-mod-viewer.appspot.com/github.com/juju/juju@v0.0.0-20240327075706-a90865de2538/provider/maas/config.go#L73: unused write to field Config https://go-mod-viewer.appspot.com/git.ug-wk.cc/server/log@v0.0.0-20230524075443-2e41d2d64cca/config.go#L146: unused write to field ErrorOutputPaths https://go-mod-viewer.appspot.com/github.com/projectdiscovery/nuclei/v2@v2.9.15/pkg/protocols/dns/dns.go#L142: unused write to field Resolvers https://go-mod-viewer.appspot.com/github.com/openfga/go-sdk@v0.3.5/client/client_test.go#L1050: unused write to field ResponseStatus https://go-mod-viewer.appspot.com/github.com/janelia-flyem/dvid@v1.0.0/datatype/multichan16/multichan16.go#L421: unused write to field channelNum https://go-mod-viewer.appspot.com/github.com/condensat/bank-core@v0.1.0/security/internal/edwards25519/edwards25519.go#L752: unused write to array index 31:int - t59 https://go-mod-viewer.appspot.com/github.com/PagerDuty/go-pagerduty@v1.8.0/service_test.go#L74: unused write to field More https://go-mod-viewer.appspot.com/github.com/fluxcd/go-git-providers@v0.19.3/gitprovider/testutils/retry.go#L86: unused write to field backoff https://go-mod-viewer.appspot.com/github.com/perimeterx/marshmallow@v1.1.5/unmarshal_test.go#L1215: unused write to field ChildField25 https://go-mod-viewer.appspot.com/gitlab.com/go-extension/tls@v0.0.0-20240304171319-e6745021905e/example_test.go#L216: unused write to field VerifyConnection https://go-mod-viewer.appspot.com/go.temporal.io/server@v1.23.0/common/rpc/test/rpc_localstore_tls_test.go#L409: unused write to field Membership https://go-mod-viewer.appspot.com/github.com/perimeterx/marshmallow@v1.1.5/unmarshal_test.go#L1151: unused write to field ChildField21 https://go-mod-viewer.appspot.com/github.com/weaviate/weaviate@v1.24.6/modules/text2vec-openai/clients/openai_test.go#L65: unused write to field ModelVersion https://go-mod-viewer.appspot.com/github.com/nacos-group/nacos-sdk-go/v2@v2.2.5/clients/naming_client/naming_cache/subscribe_callback_test.go#L75: unused write to field CacheMillis https://go-mod-viewer.appspot.com/yunion.io/x/jsonutils@v1.0.0/unmarshal.go#L81: unused write to field data https://go-mod-viewer.appspot.com/github.com/ystia/yorc/v4@v4.3.0/storage/store_mgr.go#L123: unused write to field Types https://go-mod-viewer.appspot.com/github.com/gravity-devs/liquidity@v1.5.3/x/liquidity/keeper/liquidity_pool_test.go#L263: unused write to field WithdrawFeeRate https://go-mod-viewer.appspot.com/git.ug-wk.cc/server/log@v0.0.0-20230524075443-2e41d2d64cca/config.go#L144: unused write to field Encoding https://go-mod-viewer.appspot.com/github.com/aacfactory/fns-contrib/databases/sql@v1.2.84/rows.go#L266: unused write to field Valid https://go-mod-viewer.appspot.com/github.com/prysmaticlabs/prysm@v1.4.4/slasher/detection/detect_test.go#L539: unused write to field ctx https://go-mod-viewer.appspot.com/github.com/prysmaticlabs/prysm@v1.4.4/slasher/detection/detect_test.go#L540: unused write to field cfg https://go-mod-viewer.appspot.com/github.com/hyperledger/aries-framework-go@v0.3.2/pkg/didcomm/protocol/didexchange/states_test.go#L817: unused write to field outboundDispatcher https://go-mod-viewer.appspot.com/github.com/mit-dci/lit@v0.0.0-20221102210550-8c3d3b49f2ce/wire/message.go#L279: unused write to field command https://go-mod-viewer.appspot.com/github.com/SlyMarbo/spdy@v0.0.0-20160217225201-b5edf18e002b/spdy3/io.go#L107: unused write to field StreamID https://go-mod-viewer.appspot.com/github.com/verrazzano/verrazzano@v1.7.0/application-operator/controllers/loggingtrait/loggingtrait_controller.go#L168: unused write to field ImagePullPolicy https://go-mod-viewer.appspot.com/gitlab.com/SkynetLabs/skyd@v1.6.9/skymodules/renter/skylinkdatasource_test.go#L34: unused write to field staticBaseSectorDownloadStats https://go-mod-viewer.appspot.com/github.com/projectcontour/contour@v1.28.2/cmd/contour/certgen_test.go#L190: unused write to field OutputKube https://go-mod-viewer.appspot.com/github.com/coreos/goproxy@v0.0.0-20190513173959-f8dc2d7ba04e/websocket.go#L50: unused write to field Path https://go-mod-viewer.appspot.com/sigs.k8s.io/cluster-api@v1.6.3/internal/controllers/machinehealthcheck/machinehealthcheck_targets_test.go#L170: unused write to field patchHelper https://go-mod-viewer.appspot.com/github.com/gambol99/goproxy@v0.0.0-20170612135454-e713e5909438/websocket.go#L29: unused write to field Path https://go-mod-viewer.appspot.com/github.com/KiraCore/sekai@v0.3.43/x/layer2/proposal_handler.go#L173: unused write to field UpdateTimeMax https://go-mod-viewer.appspot.com/github.com/ChainSafe/chainbridge-core@v1.4.2/chains/evm/listener/deposit-handler_test.go#L196: unused write to field SenderAddress https://go-mod-viewer.appspot.com/github.com/confluentinc/confluent-kafka-go@v1.9.2/kafka/producer_performance_test.go#L208: unused write to field Value https://go-mod-viewer.appspot.com/yunion.io/x/cloudmux@v0.3.10-0-alpha.1/pkg/multicloud/huawei/obs/client.go#L86: unused write to field httpClient https://go-mod-viewer.appspot.com/github.com/vertgenlab/gonomics@v1.0.0/genomeGraph/search.go#L124: unused write to field targetEnd https://go-mod-viewer.appspot.com/github.com/fluxcd/go-git-providers@v0.19.3/gitprovider/testutils/retry.go#L81: unused write to field interval https://go-mod-viewer.appspot.com/github.com/vishvananda/netlink@v1.1.0/nl/seg6_linux.go#L107: unused write to field routingType https://go-mod-viewer.appspot.com/github.com/IBM-Cloud/bluemix-go@v0.0.0-20240314082800-4e02a69b84b2/api/iampap/iampapv1/models.go#L191: unused write to field Value https://go-mod-viewer.appspot.com/github.com/civo/civogo@v0.3.65/firewall_test.go#L134: unused write to field InstanceCount https://go-mod-viewer.appspot.com/github.com/vertgenlab/gonomics@v1.0.0/genomeGraph/search.go#L131: unused write to field rightScore https://go-mod-viewer.appspot.com/github.com/btccom/go-micro/v2@v2.9.3/store/cockroach/cockroach.go#L251: unused write to field Expiry https://go-mod-viewer.appspot.com/honnef.co/go/tools@v0.4.7/pattern/parser.go#L304: unused write to field idx https://go-mod-viewer.appspot.com/github.com/kyma-project/control-plane/components/kyma-environment-broker@v0.0.0-20230911130701-f7d1ac254205/internal/provisioner/client_test.go#L399: unused write to field State
I took a quick look. Most of the reports in non-test code look really good.
https://go-mod-viewer.appspot.com/honnef.co/go/tools@v0.4.7/pattern/parser.go#L304
FYI there are some false positives due to struct literals:
The common pattern is x := struct{f, g int}{f: 0, g: 1}; println(x.f)
. The implicit x.g = 1
write is being reported as it is never used. The solution is likely just better representation of struct literal initialization at the SSA level and not reporting these. This could be something like what staticcheck does in its ir
, which is to have a struct literal Instruction, or better 'debug info' on the write instructions.
Just something to keep in mind. Unclear if it is urgent.
FYI there are some false positives due to struct literals:
They're not bugs, but they do indicate that a field of a struct is assigned but never used, which is a sign that the code is building a bigger data structure than it actually needs.
CL 287034 added the new
unusedwrite
analysis pass. I think it would be nice to have ingopls
.I'm not sure if it should be among the default analysers, but either way, if there are no objections to this, I am ready to send a CL.