What to do about duplicate targets in a workspace?

[ehuss]

Currently a workspace can have multiple packages with the same target names. This causes a problem if you attempt to build both targets at the same time. One will overwrite the other when it is hardlinked in the target dir, and the result is somewhat random.

This affects binaries, examples, and libraries. Tests and benchmarks have unique hashes in their names.

I'm unsure of the best way to deal with this. One option is to issue a warning if this happens (at workspace validation phase), and turn that warning into a hard error after a sufficiently long time.

Another option is to detect if you attempt to build conflicting targets and return an error explaining you can only build one at a time (with some explanation about the naming conflict).

[alexcrichton]

Hm I hadn't thought of this before! I think I'd personally be a fan of the hard error though. The result is already nondeterministic and probably broken today, so as long as we don't have any false positives from the error it seems unlikely that we'll break existing working workflows!

[ehuss]

I download ~3300 workspaces off github to see how widespread it was. I found 63 workspaces that get tripped by this error. The rust-lang/rust repo had this problem until recently (bootstrap and rustc both had a binary called rustc until @Mark-Simulacrum changed it in rust-lang/rust#50629 — though that was changed for a different reason, rustc-the-binary and librustc had .rmeta files conflicting). There are some prominent ones like tokio, a parity project, etc. Does that change your inclination about making it a hard error right away? I don't mind, I just don't want to cause too much disruption.

CLICK - list of affected workspaces

https://github.com/Hossein-Noroozpour/vulkust/tree/master error: package more-things has a bin target with the same name `main` as package hello-world

https://github.com/OpenAPITools/openapi-generator/tree/master/samples/server/petstore/rust-server
error: package rust-server-test has a example target with the same name client as package petstore-with-fake-endpoints-models-for-testing

https://github.com/vorner/spirit/tree/master
error: package spirit-hyper has a example target with the same name hws as package spirit

https://github.com/hawkw/tokio-trace-prototype/tree/master
error: package tokio-trace-slog has a example target with the same name basic as package tokio-trace

https://github.com/Arvamer/gilrs/tree/master
error: package gilrs-core has a example target with the same name ev as package gilrs

https://github.com/Avekvist/oxygen-game-engine/tree/master
error: package oxygen_electron has a example target with the same name temporary as package oxygen_bond

https://github.com/Grokmoo/sulis/tree/master
error: package sulis has a bin target with the same name main as package sulis_editor

https://github.com/diesel-rs/diesel/tree/master
error: package diesel_demo_step_2_mysql has a bin target with the same name show_posts as package diesel_demo_step_1_mysql

https://github.com/msiglreith/tanya/tree/master
error: package tanya-ui has a example target with the same name basic as package tanya-ecs2

https://github.com/tobyjsullivan/fonts/tree/master
error: package fonts has a bin target with the same name about as package about

https://github.com/tokio-rs/tokio/tree/master
error: package tokio-tls has a example target with the same name echo as package tokio

https://github.com/rust-av/opus-rs/tree/master
error: package libopus has a example target with the same name encode as package opus-sys

https://github.com/qnighy/honeybadger-rs/tree/master
error: package honeybadger-gotham has a example target with the same name server as package honeybadger-rocket

https://github.com/Nemo157/embrio-rs/tree/master
error: package pca10031 has a example target with the same name hello as package local

https://github.com/mit-pdos/noria/tree/master
error: package noria-server has a example target with the same name basic-recipe as package noria

https://github.com/sozu-proxy/sozu/tree/master
error: package sozu-command-futures has a example target with the same name main as package sozu-lib

https://github.com/dgrunwald/rust-cpython/tree/master
error: package python3-sys has a example target with the same name version as package python27-sys

https://github.com/rustkas/rust-by-example-imp/tree/master/rust-by-example
error: package types has a bin target with the same name literals as package primitives

https://github.com/sozu-proxy/lapin-futures-tls/tree/master
error: package lapin-futures-native-tls has a example target with the same name client as package lapin-futures-tls-internal

https://github.com/diwic/dbus-rs/tree/master
error: package dbus-codegen has a example target with the same name adv_server as package dbus

https://github.com/paritytech/jsonrpc/tree/master
error: package jsonrpc-minihttp-server has a example target with the same name server as package jsonrpc-http-server

https://github.com/SergioBenitez/Devise/tree/master
error: package from_form_value has a bin target with the same name main as package uri_display

https://github.com/kureuil/batch-rs/tree/master
error: package batch-example-rabbitmq-warp has a bin target with the same name worker as package batch-example-rabbitmq-standalone

https://github.com/glebpom/rust-netif/tree/master
error: package netif-bpf has a example target with the same name test as package ifcontrol

https://github.com/cogciprocate/ocl/tree/master
error: package ocl-core has a example target with the same name info_core as package ocl

https://github.com/rust-av/speexdsp-rs/tree/master
error: package speexdsp has a example target with the same name testresample as package speexdsp-sys

https://github.com/ubnt-intrepid/doubter/tree/master
error: package doctest-edition2018 has a lib target with the same name doctest as package doctest

https://github.com/lettre/lettre/tree/master
error: package lettre_email has a example target with the same name smtp as package lettre

https://github.com/weiznich/wundergraph/tree/master
error: package wundergraph_bench has a bin target with the same name main as package wundergraph_example

https://github.com/WiSaGaN/ctp-rs/tree/master
error: package ctp-trader has a example target with the same name api as package ctp-md

https://github.com/marhel/r68k/tree/master
error: package r68k-tools has a example target with the same name asm as package r68k-emu

https://github.com/dtcristo/raylib-rust/tree/master
error: package raylib-sys has a example target with the same name raylib_rust_logo as package raylib

https://github.com/Hoverbear/rust-rosetta/tree/master
error: package 24-game has a bin target with the same name main as package 100-doors

https://github.com/LevitatingOrange/oblivious-transfer/tree/master/examples
error: package beaver_triples_gen has a bin target with the same name client as package simple_transfer

https://github.com/erlepereira/x11-rs/tree/master
error: package x11-dl has a example target with the same name hello-world as package x11

https://github.com/johalun/rustkpi/tree/master/rust/rust-src-1.25.0/src
error: package rustc-main has a bin target with the same name rustc as package bootstrap

https://github.com/royallthefourth/platformsh-rust-rocket/tree/master
error: package rust-example has a bin target with the same name backend as package backend

https://github.com/George3d6/Inquisitor/tree/master
error: package receptor_plugins has a lib target with the same name plugins as package agent_plugins

https://github.com/hhatto/rust-snippets/tree/master/extension
error: package pyo3-woothee has a lib target with the same name woothee as package fast-woothee

https://github.com/little-dude/netlink/tree/master
error: package rtnetlink has a example target with the same name dump_links as package iproute2

https://github.com/king6cong/moon/tree/master
error: package c_replace has a bin target with the same name render as package c_markdown

https://github.com/tailhook/abstract-ns/tree/master
error: package ns-dns-tokio has a example target with the same name resolve as package ns-std-threaded

https://github.com/elastic-rs/elastic/tree/master
error: package elastic_reqwest has a example target with the same name basic_async as package elastic

https://github.com/kabelyang/Parity-JSON-RPC/tree/master
error: package jsonrpc-minihttp-server has a example target with the same name server as package jsonrpc-http-server

https://github.com/gretchenfrage/ws_problem/tree/master
error: package workspace_test has a bin target with the same name root as package root

https://github.com/mimirblockchainsolutions/mimir-rust-alpha/tree/master
error: package mimir-requester has a example target with the same name simple as package pubnub-hyper

https://github.com/benywan/jsonrpc/tree/master
error: package jsonrpc-minihttp-server has a example target with the same name server as package jsonrpc-http-server

https://github.com/akashche/itw_win_devkit/tree/master/rust/src
error: package rustc-main has a bin target with the same name rustc as package bootstrap

https://github.com/stefan-k/kraxn/tree/master
error: package kraxn has a bin target with the same name kraxn-server as package kraxn-server

https://github.com/jjpe/amplify/tree/master
error: package amplify has a bin target with the same name amplify as package amplify-core

https://github.com/super-string/jsonrpc/tree/master
error: package jsonrpc-minihttp-server has a example target with the same name server as package jsonrpc-http-server

https://github.com/randomPoison/polygon/tree/master
error: package gl-util has a example target with the same name hello_triangle as package polygon

https://github.com/mob-rs/mob/tree/master
error: package mob_server has a bin target with the same name main as package mob

https://github.com/ryoon/rustc-1.19.0/tree/master/src
error: package rustc-main has a bin target with the same name rustc as package bootstrap

https://github.com/KeenS/onigmo-rs/tree/master
error: package onigmo has a example target with the same name simple as package onigmo-sys

https://github.com/sorpaas/devp2p-rs/tree/master
error: package rlpx has a example target with the same name local_connect as package dpt

https://github.com/sujayakar/rust-rt/tree/master/rust-cpython
error: package python3-sys has a example target with the same name version as package python27-sys

https://github.com/combustion-engine/combustion/tree/master
error: package combustion_window has a example target with the same name glfw as package combustion_backend

https://github.com/aidanhs/rust-appveyor/tree/master/src
error: package rustc-main has a bin target with the same name rustc as package bootstrap

https://github.com/zzeroo/ArcadeRS-1.0/tree/master
error: package arcade-rs-1-5 has a example target with the same name thing as package arcade-rs-1-4

https://github.com/JBisnett/rust-mir-plugin/tree/master/src
error: package rustc-main has a bin target with the same name rustc as package bootstrap

https://github.com/Metadiff/gir/tree/master
error: package gir_af has a bin target with the same name test as package gir_core

https://github.com/lazybox/lazybox/tree/master
error: package lazybox_settings has a example target with the same name simple as package lazybox_inputs

[alexcrichton]

Hm that's quite a few! I wonder, though, if we can still get away with making this a hard error. If we change it to say that in one build if more than one binary of the same name is produced with the same name that's an error, then that may mostly cover our bases. Today's behavior is "pretty wrong" in the sense that it's just giving you a random binary with the right name, so it seems unlikely that anyone's build steps are building the same named binary in the same build step.

I think it's probably best though, given this data, to start with a warning. I think the warning should be scoped to only where we'd want a hard error eventually (probably only for when you're building two binaries of the same name, not if they just exist in a workspace).