[gentoo-dev] [PATCH 0/5] cargo.eclass: optimizations

[gentoo-dev] [PATCH 0/5] cargo.eclass: optimizations

[Michał Górny]

Hi,

cargo.eclass is one of the slowest eclasses in ::gentoo, and does some
pretty heavy processing in global scope.  Here's a series of patches
to optimize its behavior.

Unfortunately, the optimizations cannot be done without changing
the API.  However, the series preserves backwards compatibility --
existing ebuilds will simply remain slower.

The two main changes are:

1. Replacing subshell-based `$(cargo_crate_uris)` with global variable
   `${CARGO_CRATE_URIS}`.  This requires that `CRATES` and `GIT_CRATES`
   are defined prior to inherit -- this was already the case
   for the former, and only one case of `GIT_CRATES` does not conform.
   If they're not, then the variable will simply be empty but the old
   function will still work.

2. Supporting separate crate names from versions using a forward slash
   rather than a hyphen.  This makes it possible to parse the crate list
   using a simple cutting rather than regular expressions.  Again,
   existing syntax continues working but it remains much slower.

To compare, the initial timings for the eclass give, using the 52 CRATES
from dev-python/cryptography:

    real  252 it/s
    user  289 it/s

While the timings for fully optimized form (using variable and slashes)
give:

    real  952 it/s
    user  952 it/s


-- 
Best regards,
Michał Górny

Michał Górny (5):
  eclass/tests: Add a minimal benchmark for cargo.eclass
  cargo.eclass: Add variable alternative to $(cargo_crate_uris)
  cargo.eclass: Optimize GIT_CRATES check
  cargo.eclass: Support separating crate names/versions via slash
  cargo.eclass: Mark GIT_CRATES as pre-inherit

 eclass/cargo.eclass         | 127 ++++++++++++++++++++++--------------
 eclass/tests/cargo-bench.sh | 114 ++++++++++++++++++++++++++++++++
 2 files changed, 192 insertions(+), 49 deletions(-)
 create mode 100755 eclass/tests/cargo-bench.sh

-- 
2.41.0

[gentoo-dev] [PATCH 1/5] eclass/tests: Add a minimal benchmark for cargo.eclass

[Michał Górny]

The initial results on my machine are:

```
real  252 it/s
user  289 it/s
```

Signed-off-by: Michał Górny <mgorny@gentoo.org>
---
 eclass/tests/cargo-bench.sh | 107 ++++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100755 eclass/tests/cargo-bench.sh

diff --git a/eclass/tests/cargo-bench.sh b/eclass/tests/cargo-bench.sh
new file mode 100755
index 000000000000..cdc5e4431c14
--- /dev/null
+++ b/eclass/tests/cargo-bench.sh
@@ -0,0 +1,107 @@
+#!/bin/bash
+# Copyright 2023 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+source tests-common.sh || exit
+
+export LC_ALL=C
+
+ITERATIONS=1000
+RUNS=3
+
+doit() {
+	for (( i = 0; i < ITERATIONS; i++ )); do
+		SRC_URI="
+			$(cargo_crate_uris)
+		"
+	done
+}
+
+timeit() {
+	local real=()
+	local user=()
+	local x vr avg
+
+	for (( x = 0; x < RUNS; x++ )); do
+		while read tt tv; do
+			case ${tt} in
+				real) real+=( ${tv} );;
+				user) user+=( ${tv} );;
+			esac
+		done < <( ( time -p doit ) 2>&1 )
+	done
+
+	[[ ${#real[@]} == ${RUNS} ]] || die "Did not get ${RUNS} real times"
+	[[ ${#user[@]} == ${RUNS} ]] || die "Did not get ${RUNS} user times"
+
+	local xr avg
+	for x in real user; do
+		xr="${x}[*]"
+		avg=$(dc -S 3 -e "${ITERATIONS} ${RUNS} * ${!xr} + + / p")
+
+		printf '%s %4.0f it/s\n' "${x}" "${avg}"
+	done
+}
+
+# taken from cryptograpy-41.0.1
+CRATES="
+	Inflector-0.11.4
+	aliasable-0.1.3
+	asn1-0.15.2
+	asn1_derive-0.15.2
+	autocfg-1.1.0
+	base64-0.13.1
+	bitflags-1.3.2
+	cc-1.0.79
+	cfg-if-1.0.0
+	foreign-types-0.3.2
+	foreign-types-shared-0.1.1
+	indoc-1.0.9
+	libc-0.2.144
+	lock_api-0.4.9
+	memoffset-0.8.0
+	once_cell-1.17.2
+	openssl-0.10.54
+	openssl-macros-0.1.1
+	openssl-sys-0.9.88
+	ouroboros-0.15.6
+	ouroboros_macro-0.15.6
+	parking_lot-0.12.1
+	parking_lot_core-0.9.7
+	pem-1.1.1
+	pkg-config-0.3.27
+	proc-macro-error-1.0.4
+	proc-macro-error-attr-1.0.4
+	proc-macro2-1.0.59
+	pyo3-0.18.3
+	pyo3-build-config-0.18.3
+	pyo3-ffi-0.18.3
+	pyo3-macros-0.18.3
+	pyo3-macros-backend-0.18.3
+	quote-1.0.28
+	redox_syscall-0.2.16
+	scopeguard-1.1.0
+	smallvec-1.10.0
+	syn-1.0.109
+	syn-2.0.18
+	target-lexicon-0.12.7
+	unicode-ident-1.0.9
+	unindent-0.1.11
+	vcpkg-0.2.15
+	version_check-0.9.4
+	windows-sys-0.45.0
+	windows-targets-0.42.2
+	windows_aarch64_gnullvm-0.42.2
+	windows_aarch64_msvc-0.42.2
+	windows_i686_gnu-0.42.2
+	windows_i686_msvc-0.42.2
+	windows_x86_64_gnu-0.42.2
+	windows_x86_64_gnullvm-0.42.2
+	windows_x86_64_msvc-0.42.2
+"
+
+inherit cargo
+timeit
+
+texit
-- 
2.41.0

[gentoo-dev] [PATCH 2/5] cargo.eclass: Add variable alternative to $(cargo_crate_uris)

[Michał Górny]

Add a helper function that sets ${CARGO_CRATE_URIS} variable to make
it possible to set SRC_URI without subshells.  This gives a slight
speedup (~20%):

```
real  300 it/s
user  324 it/s
```

Signed-off-by: Michał Górny <mgorny@gentoo.org>
---
 eclass/cargo.eclass         | 48 +++++++++++++++++++++++++------------
 eclass/tests/cargo-bench.sh |  4 +++-
 2 files changed, 36 insertions(+), 16 deletions(-)

diff --git a/eclass/cargo.eclass b/eclass/cargo.eclass
index 991e808d453f..4e0cd1e4de70 100644
--- a/eclass/cargo.eclass
+++ b/eclass/cargo.eclass
@@ -68,7 +68,7 @@ ECARGO_VENDOR="${ECARGO_HOME}/gentoo"
 # "
 # inherit cargo
 # ...
-# SRC_URI="$(cargo_crate_uris)"
+# SRC_URI="${CARGO_CRATE_URIS}"
 # @CODE
 
 # @ECLASS_VARIABLE: GIT_CRATES
@@ -162,31 +162,31 @@ ECARGO_VENDOR="${ECARGO_HOME}/gentoo"
 # group, and then switch over to building with FEATURES=userpriv.
 # Or vice-versa.
 
-# @FUNCTION: cargo_crate_uris
+# @ECLASS_VARIABLE: CARGO_CRATE_URIS
+# @OUTPUT_VARIABLE
+# @DESCRIPTION:
+# List of URIs to put in SRC_URI created from CRATES variable.
+
+# @FUNCTION: _cargo_set_crate_uris
+# @USAGE: <crates>
 # @DESCRIPTION:
 # Generates the URIs to put in SRC_URI to help fetch dependencies.
 # Constructs a list of crates from its arguments.
 # If no arguments are provided, it uses the CRATES variable.
-cargo_crate_uris() {
+# The value is set as CARGO_CRATE_URIS.
+_cargo_set_crate_uris() {
 	local -r regex='^([a-zA-Z0-9_\-]+)-([0-9]+\.[0-9]+\.[0-9]+.*)$'
-	local crate crates
-
-	if [[ -n ${@} ]]; then
-		crates="$@"
-	elif [[ -n ${CRATES} ]]; then
-		crates="${CRATES}"
-	else
-		eerror "CRATES variable is not defined and nothing passed as argument"
-		die "Can't generate SRC_URI from empty input"
-	fi
+	local crates=${1}
+	local crate
 
+	CARGO_CRATE_URIS=
 	for crate in ${crates}; do
 		local name version url
 		[[ $crate =~ $regex ]] || die "Could not parse name and version from crate: $crate"
 		name="${BASH_REMATCH[1]}"
 		version="${BASH_REMATCH[2]}"
 		url="https://crates.io/api/v1/crates/${name}/${version}/download -> ${crate}.crate"
-		echo "${url}"
+		CARGO_CRATE_URIS+="${url} "
 	done
 
 	local git_crates_type
@@ -214,12 +214,30 @@ cargo_crate_uris() {
 				;;
 			esac
 
-			printf -- '%s -> %s\n' "${crate_uri//%commit%/${commit}}" "${repo_name}-${commit}${repo_ext}.tar.gz"
+			CARGO_CRATE_URIS+="${crate_uri//%commit%/${commit}} -> ${repo_name}-${commit}${repo_ext}.tar.gz "
 		done
 	elif [[ -n ${git_crates_type} ]]; then
 		die "GIT_CRATE must be declared as an associative array"
 	fi
 }
+_cargo_set_crate_uris "${CRATES}"
+
+# @FUNCTION: cargo_crate_uris
+# @USAGE: [<crates>...]
+# @DESCRIPTION:
+# Generates the URIs to put in SRC_URI to help fetch dependencies.
+# Constructs a list of crates from its arguments.
+# If no arguments are provided, it uses the CRATES variable.
+cargo_crate_uris() {
+	local crates=${*-${CRATES}}
+	if [[ -z ${crates} ]]; then
+		eerror "CRATES variable is not defined and nothing passed as argument"
+		die "Can't generate SRC_URI from empty input"
+	fi
+
+	_cargo_set_crate_uris "${crates}"
+	echo "${CARGO_CRATE_URIS}"
+}
 
 # @FUNCTION: cargo_gen_config
 # @DESCRIPTION:
diff --git a/eclass/tests/cargo-bench.sh b/eclass/tests/cargo-bench.sh
index cdc5e4431c14..11b740f8dfcd 100755
--- a/eclass/tests/cargo-bench.sh
+++ b/eclass/tests/cargo-bench.sh
@@ -12,8 +12,9 @@ RUNS=3
 
 doit() {
 	for (( i = 0; i < ITERATIONS; i++ )); do
+		_cargo_set_crate_uris "${CRATES}"
 		SRC_URI="
-			$(cargo_crate_uris)
+			${CARGO_CRATE_URIS}
 		"
 	done
 }
@@ -102,6 +103,7 @@ CRATES="
 "
 
 inherit cargo
+
 timeit
 
 texit
-- 
2.41.0

[gentoo-dev] [PATCH 3/5] cargo.eclass: Optimize GIT_CRATES check

[Michał Górny]

Optimize the GIT_CRATES check to call `declare -p` only if the variable
is actually set.  In the vast majority of ebuilds using cargo.eclass,
it's not set, so the subshell-first approach is slowing things down.
With this change, the speed improves by another ~20%:

```
real  363 it/s
user  365 it/s
```

Signed-off-by: Michał Górny <mgorny@gentoo.org>
---
 eclass/cargo.eclass | 58 ++++++++++++++++++++++-----------------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/eclass/cargo.eclass b/eclass/cargo.eclass
index 4e0cd1e4de70..d97bb0df9348 100644
--- a/eclass/cargo.eclass
+++ b/eclass/cargo.eclass
@@ -189,35 +189,35 @@ _cargo_set_crate_uris() {
 		CARGO_CRATE_URIS+="${url} "
 	done
 
-	local git_crates_type
-	git_crates_type="$(declare -p GIT_CRATES 2>&-)"
-	if [[ ${git_crates_type} == "declare -A "* ]]; then
-		local crate commit crate_uri crate_dir repo_ext feat_expr
-
-		for crate in "${!GIT_CRATES[@]}"; do
-			IFS=';' read -r crate_uri commit crate_dir <<< "${GIT_CRATES[${crate}]}"
-
-			case "${crate_uri}" in
-				https://github.com/*)
-					repo_ext=".gh"
-					repo_name="${crate_uri##*/}"
-					crate_uri="${crate_uri%/}/archive/%commit%.tar.gz"
-				;;
-				https://gitlab.com/*)
-					repo_ext=".gl"
-					repo_name="${crate_uri##*/}"
-					crate_uri="${crate_uri%/}/-/archive/%commit%/${repo_name}-%commit%.tar.gz"
-				;;
-				*)
-					repo_ext=
-					repo_name="${crate}"
-				;;
-			esac
-
-			CARGO_CRATE_URIS+="${crate_uri//%commit%/${commit}} -> ${repo_name}-${commit}${repo_ext}.tar.gz "
-		done
-	elif [[ -n ${git_crates_type} ]]; then
-		die "GIT_CRATE must be declared as an associative array"
+	if declare -p GIT_CRATES &>/dev/null; then
+		if [[ $(declare -p GIT_CRATES) == "declare -A"* ]]; then
+			local crate commit crate_uri crate_dir repo_ext feat_expr
+
+			for crate in "${!GIT_CRATES[@]}"; do
+				IFS=';' read -r crate_uri commit crate_dir <<< "${GIT_CRATES[${crate}]}"
+
+				case "${crate_uri}" in
+					https://github.com/*)
+						repo_ext=".gh"
+						repo_name="${crate_uri##*/}"
+						crate_uri="${crate_uri%/}/archive/%commit%.tar.gz"
+					;;
+					https://gitlab.com/*)
+						repo_ext=".gl"
+						repo_name="${crate_uri##*/}"
+						crate_uri="${crate_uri%/}/-/archive/%commit%/${repo_name}-%commit%.tar.gz"
+					;;
+					*)
+						repo_ext=
+						repo_name="${crate}"
+					;;
+				esac
+
+				CARGO_CRATE_URIS+="${crate_uri//%commit%/${commit}} -> ${repo_name}-${commit}${repo_ext}.tar.gz "
+			done
+		else
+			die "GIT_CRATE must be declared as an associative array"
+		fi
 	fi
 }
 _cargo_set_crate_uris "${CRATES}"
-- 
2.41.0

[gentoo-dev] [PATCH 4/5] cargo.eclass: Support separating crate names/versions via slash

[Michał Górny]

Support specifying crate names and versions separated by forward slashes
rather than hyphens.  Since slashes are not valid in crate names, this
makes splitting the tokens trivial and free of regular expressions.
Effectively, the slash variant is roughly 180% faster:

```
 * CRATES with slashes
real  952 it/s
user  952 it/s
 * CRATES with hyphens
real  339 it/s
user  339 it/s
```

Signed-off-by: Michał Górny <mgorny@gentoo.org>
---
 eclass/cargo.eclass         |  24 +++++---
 eclass/tests/cargo-bench.sh | 111 +++++++++++++++++++-----------------
 2 files changed, 75 insertions(+), 60 deletions(-)

diff --git a/eclass/cargo.eclass b/eclass/cargo.eclass
index d97bb0df9348..54a1edd36c28 100644
--- a/eclass/cargo.eclass
+++ b/eclass/cargo.eclass
@@ -59,12 +59,16 @@ ECARGO_VENDOR="${ECARGO_HOME}/gentoo"
 # Bash string containing all crates that are to be downloaded.
 # It is used by cargo_crate_uris.
 #
+# Ideally, crate names and versions should be separated by a forward
+# slash.  A legacy syntax using hyphen is also supported but it is much
+# slower.
+#
 # Example:
 # @CODE
 # CRATES="
-# metal-1.2.3
-# bar-4.5.6
-# iron_oxide-0.0.1
+# metal/1.2.3
+# bar/4.5.6
+# iron_oxide/0.0.1
 # "
 # inherit cargo
 # ...
@@ -182,10 +186,16 @@ _cargo_set_crate_uris() {
 	CARGO_CRATE_URIS=
 	for crate in ${crates}; do
 		local name version url
-		[[ $crate =~ $regex ]] || die "Could not parse name and version from crate: $crate"
-		name="${BASH_REMATCH[1]}"
-		version="${BASH_REMATCH[2]}"
-		url="https://crates.io/api/v1/crates/${name}/${version}/download -> ${crate}.crate"
+		if [[ ${crate} == */* ]]; then
+			name=${crate%/*}
+			version=${crate##*/}
+		else
+			[[ ${crate} =~ ${regex} ]] ||
+				die "Could not parse name and version from crate: ${crate}"
+			name="${BASH_REMATCH[1]}"
+			version="${BASH_REMATCH[2]}"
+		fi
+		url="https://crates.io/api/v1/crates/${name}/${version}/download -> ${name}-${version}.crate"
 		CARGO_CRATE_URIS+="${url} "
 	done
 
diff --git a/eclass/tests/cargo-bench.sh b/eclass/tests/cargo-bench.sh
index 11b740f8dfcd..cb346178f0a2 100755
--- a/eclass/tests/cargo-bench.sh
+++ b/eclass/tests/cargo-bench.sh
@@ -47,63 +47,68 @@ timeit() {
 
 # taken from cryptograpy-41.0.1
 CRATES="
-	Inflector-0.11.4
-	aliasable-0.1.3
-	asn1-0.15.2
-	asn1_derive-0.15.2
-	autocfg-1.1.0
-	base64-0.13.1
-	bitflags-1.3.2
-	cc-1.0.79
-	cfg-if-1.0.0
-	foreign-types-0.3.2
-	foreign-types-shared-0.1.1
-	indoc-1.0.9
-	libc-0.2.144
-	lock_api-0.4.9
-	memoffset-0.8.0
-	once_cell-1.17.2
-	openssl-0.10.54
-	openssl-macros-0.1.1
-	openssl-sys-0.9.88
-	ouroboros-0.15.6
-	ouroboros_macro-0.15.6
-	parking_lot-0.12.1
-	parking_lot_core-0.9.7
-	pem-1.1.1
-	pkg-config-0.3.27
-	proc-macro-error-1.0.4
-	proc-macro-error-attr-1.0.4
-	proc-macro2-1.0.59
-	pyo3-0.18.3
-	pyo3-build-config-0.18.3
-	pyo3-ffi-0.18.3
-	pyo3-macros-0.18.3
-	pyo3-macros-backend-0.18.3
-	quote-1.0.28
-	redox_syscall-0.2.16
-	scopeguard-1.1.0
-	smallvec-1.10.0
-	syn-1.0.109
-	syn-2.0.18
-	target-lexicon-0.12.7
-	unicode-ident-1.0.9
-	unindent-0.1.11
-	vcpkg-0.2.15
-	version_check-0.9.4
-	windows-sys-0.45.0
-	windows-targets-0.42.2
-	windows_aarch64_gnullvm-0.42.2
-	windows_aarch64_msvc-0.42.2
-	windows_i686_gnu-0.42.2
-	windows_i686_msvc-0.42.2
-	windows_x86_64_gnu-0.42.2
-	windows_x86_64_gnullvm-0.42.2
-	windows_x86_64_msvc-0.42.2
+	Inflector/0.11.4
+	aliasable/0.1.3
+	asn1/0.15.2
+	asn1_derive/0.15.2
+	autocfg/1.1.0
+	base64/0.13.1
+	bitflags/1.3.2
+	cc/1.0.79
+	cfg-if/1.0.0
+	foreign-types/0.3.2
+	foreign-types-shared/0.1.1
+	indoc/1.0.9
+	libc/0.2.144
+	lock_api/0.4.9
+	memoffset/0.8.0
+	once_cell/1.17.2
+	openssl/0.10.54
+	openssl-macros/0.1.1
+	openssl-sys/0.9.88
+	ouroboros/0.15.6
+	ouroboros_macro/0.15.6
+	parking_lot/0.12.1
+	parking_lot_core/0.9.7
+	pem/1.1.1
+	pkg-config/0.3.27
+	proc-macro-error/1.0.4
+	proc-macro-error-attr/1.0.4
+	proc-macro2/1.0.59
+	pyo3/0.18.3
+	pyo3-build-config/0.18.3
+	pyo3-ffi/0.18.3
+	pyo3-macros/0.18.3
+	pyo3-macros-backend/0.18.3
+	quote/1.0.28
+	redox_syscall/0.2.16
+	scopeguard/1.1.0
+	smallvec/1.10.0
+	syn/1.0.109
+	syn/2.0.18
+	target-lexicon/0.12.7
+	unicode-ident/1.0.9
+	unindent/0.1.11
+	vcpkg/0.2.15
+	version_check/0.9.4
+	windows-sys/0.45.0
+	windows-targets/0.42.2
+	windows_aarch64_gnullvm/0.42.2
+	windows_aarch64_msvc/0.42.2
+	windows_i686_gnu/0.42.2
+	windows_i686_msvc/0.42.2
+	windows_x86_64_gnu/0.42.2
+	windows_x86_64_gnullvm/0.42.2
+	windows_x86_64_msvc/0.42.2
 "
 
 inherit cargo
 
+einfo "CRATES with slashes"
+timeit
+
+einfo "CRATES with hyphens"
+CRATES=${CRATES//\//-}
 timeit
 
 texit
-- 
2.41.0

[gentoo-dev] [PATCH 5/5] cargo.eclass: Mark GIT_CRATES as pre-inherit

[Michał Górny]

The variable needs to be set before inherit in order for
${CARGO_CRATE_URIS} to be set correctly.  Currently all ebuilds using
GIT_CRATES except for one define it pre-inherit anyway, and this makes
it consistent with CRATES.

Signed-off-by: Michał Górny <mgorny@gentoo.org>
---
 eclass/cargo.eclass | 1 +
 1 file changed, 1 insertion(+)

diff --git a/eclass/cargo.eclass b/eclass/cargo.eclass
index 54a1edd36c28..60981d415c27 100644
--- a/eclass/cargo.eclass
+++ b/eclass/cargo.eclass
@@ -77,6 +77,7 @@ ECARGO_VENDOR="${ECARGO_HOME}/gentoo"
 
 # @ECLASS_VARIABLE: GIT_CRATES
 # @DEFAULT_UNSET
+# @PRE_INHERIT
 # @DESCRIPTION:
 # Bash associative array containing all of the crates that are to be
 # fetched via git.  It is used by cargo_crate_uris.
-- 
2.41.0

Re: [gentoo-dev] [PATCH 4/5] cargo.eclass: Support separating crate names/versions via slash

[Denis Lisov]

Hello Michał,

On Fri, Jun 16, 2023 at 3:09 PM Michał Górny <mgorny@gentoo.org> wrote:
> Support specifying crate names and versions separated by forward slashes
> rather than hyphens.  Since slashes are not valid in crate names, this
> makes splitting the tokens trivial and free of regular expressions.
> Effectively, the slash variant is roughly 180% faster:

As a developer using Rust I want to note that Cargo has a concept of
"package ID specification"[1] that usually uses pkgname@version
syntax, but AFAIK there's no prior art for using pkgname/version in
the ecosystem. Could it make sense to use pkgname@version for
consistency?

Regards,
Denis Lisov.

[1]: https://doc.rust-lang.org/cargo/reference/pkgid-spec.html

Re: [gentoo-dev] [PATCH 4/5] cargo.eclass: Support separating crate names/versions via slash

[Michał Górny]

On Fri, 2023-06-16 at 17:48 +0300, Denis Lisov wrote:
> Hello Michał,
> 
> On Fri, Jun 16, 2023 at 3:09 PM Michał Górny <mgorny@gentoo.org> wrote:
> > Support specifying crate names and versions separated by forward slashes
> > rather than hyphens.  Since slashes are not valid in crate names, this
> > makes splitting the tokens trivial and free of regular expressions.
> > Effectively, the slash variant is roughly 180% faster:
> 
> As a developer using Rust I want to note that Cargo has a concept of
> "package ID specification"[1] that usually uses pkgname@version
> syntax, but AFAIK there's no prior art for using pkgname/version in
> the ecosystem. Could it make sense to use pkgname@version for
> consistency?
> 

I suppose so.  The only reason I've used slash is because that could be
used directly in URL.

-- 
Best regards,
Michał Górny

Re: [gentoo-dev] [PATCH 4/5] cargo.eclass: Support separating crate names/versions via slash

[Sam James]

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Michał Górny <mgorny@gentoo.org> writes:

> On Fri, 2023-06-16 at 17:48 +0300, Denis Lisov wrote:
>> Hello Michał,
>> 
>> On Fri, Jun 16, 2023 at 3:09 PM Michał Górny <mgorny@gentoo.org> wrote:
>> > Support specifying crate names and versions separated by forward slashes
>> > rather than hyphens.  Since slashes are not valid in crate names, this
>> > makes splitting the tokens trivial and free of regular expressions.
>> > Effectively, the slash variant is roughly 180% faster:
>> 
>> As a developer using Rust I want to note that Cargo has a concept of
>> "package ID specification"[1] that usually uses pkgname@version
>> syntax, but AFAIK there's no prior art for using pkgname/version in
>> the ecosystem. Could it make sense to use pkgname@version for
>> consistency?
>> 
>
> I suppose so.  The only reason I've used slash is because that could be
> used directly in URL.

I think we should do it (@ delimiter) - it looks more natural in a Rust/cargo context.

Thanks for the suggestion!

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