feat(toml): Allow version-less manifests

src/cargo/ops/registry/publish.rs

@@ -103,7 +103,7 @@ pub fn publish(ws: &Workspace<'_>, opts: &PublishOpts<'_>) -> CargoResult<()> {
         if allowed_registries.is_empty() {
             bail!(
                 "`{}` cannot be published.\n\
-                 `package.publish` is set to `false` or an empty list in Cargo.toml and prevents publishing.",
+                 `package.publish` must be set to `true` or a non-empty list in Cargo.toml to publish.",
                 pkg.name(),
             );
         } else if !allowed_registries.contains(&reg_name) {

src/cargo/util/toml/embedded.rs

@@ -6,8 +6,6 @@ use crate::Config;
 
 const DEFAULT_EDITION: crate::core::features::Edition =
     crate::core::features::Edition::LATEST_STABLE;
-const DEFAULT_VERSION: &str = "0.0.0";
-const DEFAULT_PUBLISH: bool = false;
 const AUTO_FIELDS: &[&str] = &["autobins", "autoexamples", "autotests", "autobenches"];
 
 pub fn expand_manifest(
@@ -123,9 +121,6 @@ fn expand_manifest_(
     package
         .entry("name".to_owned())
         .or_insert(toml::Value::String(name));
-    package
-        .entry("version".to_owned())
-        .or_insert_with(|| toml::Value::String(DEFAULT_VERSION.to_owned()));
     package.entry("edition".to_owned()).or_insert_with(|| {
         let _ = config.shell().warn(format_args!(
             "`package.edition` is unspecified, defaulting to `{}`",
@@ -136,9 +131,6 @@ fn expand_manifest_(
     package
         .entry("build".to_owned())
         .or_insert_with(|| toml::Value::Boolean(false));
-    package
-        .entry("publish".to_owned())
-        .or_insert_with(|| toml::Value::Boolean(DEFAULT_PUBLISH));
     for field in AUTO_FIELDS {
         package
             .entry(field.to_owned())
@@ -621,8 +613,6 @@ autotests = false
 build = false
 edition = "2021"
 name = "test-"
-publish = false
-version = "0.0.0"
 
 [profile.release]
 strip = true
@@ -651,8 +641,6 @@ autotests = false
 build = false
 edition = "2021"
 name = "test-"
-publish = false
-version = "0.0.0"
 
 [profile.release]
 strip = true

src/cargo/util/toml/mod.rs

@@ -550,11 +550,17 @@ impl TomlManifest {
         let version = package
             .version
             .clone()
-            .resolve("version", || inherit()?.version())?;
+            .map(|version| version.resolve("version", || inherit()?.version()))
+            .transpose()?;
 
-        package.version = MaybeWorkspace::Defined(version.clone());
+        package.version = version.clone().map(MaybeWorkspace::Defined);
 
-        let pkgid = package.to_package_id(source_id, version)?;
+        let pkgid = package.to_package_id(
+            source_id,
+            version
+                .clone()
+                .unwrap_or_else(|| semver::Version::new(0, 0, 0)),
+        )?;
 
         let edition = if let Some(edition) = package.edition.clone() {
             let edition: Edition = edition
@@ -1006,9 +1012,14 @@ impl TomlManifest {
         let publish = match publish {
             Some(VecStringOrBool::VecString(ref vecstring)) => Some(vecstring.clone()),
             Some(VecStringOrBool::Bool(false)) => Some(vec![]),
-            None | Some(VecStringOrBool::Bool(true)) => None,
+            Some(VecStringOrBool::Bool(true)) => None,
+            None => version.is_none().then_some(vec![]),
         };
 
+        if version.is_none() && publish != Some(vec![]) {
+            bail!("`package.publish` requires `package.version` be specified");
+        }
+
         if summary.features().contains_key("default-features") {
             warnings.push(
                 "`default-features = [\"..\"]` was found in [features]. \
@@ -1659,8 +1670,7 @@ pub struct TomlPackage {
     edition: Option<MaybeWorkspaceString>,
     rust_version: Option<MaybeWorkspaceRustVersion>,
     name: InternedString,
-    #[serde(deserialize_with = "version_trim_whitespace")]
-    version: MaybeWorkspaceSemverVersion,
+    version: Option<MaybeWorkspaceSemverVersion>,
     authors: Option<MaybeWorkspaceVecString>,
     build: Option<StringOrBool>,
     metabuild: Option<StringOrVec>,
@@ -1709,22 +1719,6 @@ impl TomlPackage {
     }
 }
 
-fn version_trim_whitespace<'de, D>(deserializer: D) -> Result<MaybeWorkspaceSemverVersion, D::Error>
-where
-    D: de::Deserializer<'de>,
-{
-    UntaggedEnumVisitor::new()
-        .expecting("SemVer version")
-        .string(
-            |value| match value.trim().parse().map_err(de::Error::custom) {
-                Ok(parsed) => Ok(MaybeWorkspace::Defined(parsed)),
-                Err(e) => Err(e),
-            },
-        )
-        .map(|value| value.deserialize().map(MaybeWorkspace::Workspace))
-        .deserialize(deserializer)
-}
-
 /// This Trait exists to make [`MaybeWorkspace::Workspace`] generic. It makes deserialization of
 /// [`MaybeWorkspace`] much easier, as well as making error messages for
 /// [`MaybeWorkspace::resolve`] much nicer
@@ -1793,6 +1787,23 @@ impl<T, W: WorkspaceInherit> MaybeWorkspace<T, W> {
 
 //. This already has a `Deserialize` impl from version_trim_whitespace
 type MaybeWorkspaceSemverVersion = MaybeWorkspace<semver::Version, TomlWorkspaceField>;
+impl<'de> de::Deserialize<'de> for MaybeWorkspaceSemverVersion {
+    fn deserialize<D>(d: D) -> Result<Self, D::Error>
+    where
+        D: de::Deserializer<'de>,
+    {
+        UntaggedEnumVisitor::new()
+            .expecting("SemVer version")
+            .string(
+                |value| match value.trim().parse().map_err(de::Error::custom) {
+                    Ok(parsed) => Ok(MaybeWorkspace::Defined(parsed)),
+                    Err(e) => Err(e),
+                },
+            )
+            .map(|value| value.deserialize().map(MaybeWorkspace::Workspace))
+            .deserialize(d)
+    }
+}
 
 type MaybeWorkspaceString = MaybeWorkspace<String, TomlWorkspaceField>;
 impl<'de> de::Deserialize<'de> for MaybeWorkspaceString {

src/doc/src/reference/manifest.md

@@ -109,6 +109,8 @@ resolve dependencies, and for guidelines on setting your own version. See the
 [SemVer compatibility] chapter for more details on exactly what constitutes a
 breaking change.
 
+This field is optional and defaults to `0.0.0`.  The field is required for publishing packages.
+
 [Resolver]: resolver.md
 [SemVer compatibility]: semver.md
 
@@ -470,23 +472,22 @@ if any of those files change.
 
 ### The `publish` field
 
-The `publish` field can be used to prevent a package from being published to a
-package registry (like *crates.io*) by mistake, for instance to keep a package
-private in a company.
-
+The `publish` field can be used to control which registries names the package
+may be published to:
 ```toml
 [package]
 # ...
-publish = false
+publish = ["some-registry-name"]
 ```
 
-The value may also be an array of strings which are registry names that are
-allowed to be published to.
-
+To prevent a package from being published to a registry (like crates.io) by mistake,
+for instance to keep a package private in a company,
+you can omit the [`version`](#the-version-field) field.
+If you'd like to be more explicit, you can disable publishing:
 ```toml
 [package]
 # ...
-publish = ["some-registry-name"]
+publish = false
 ```
 
 If publish array contains a single registry, `cargo publish` command will use

src/doc/src/reference/unstable.md

@@ -1221,9 +1221,6 @@ at the start of the infostring at the top of the file.
 
 Inferred / defaulted manifest fields:
 - `package.name = <slugified file stem>`
-- `package.version = "0.0.0"` to [call attention to this crate being used in unexpected places](https://matklad.github.io/2021/08/22/large-rust-workspaces.html#Smaller-Tips)
-- `package.publish = false` to avoid accidental publishes, particularly if we
-  later add support for including them in a workspace.
 - `package.edition = <current>` to avoid always having to add an embedded
   manifest at the cost of potentially breaking scripts on rust upgrades
   - Warn when `edition` is unspecified to raise awareness of this

tests/testsuite/check.rs

@@ -1496,3 +1496,26 @@ fn check_unused_manifest_keys() {
         )
         .run();
 }
+
+#[cargo_test]
+fn versionless_package() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                description = "foo"
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+    p.cargo("check")
+        .with_stderr(
+            "\
+[CHECKING] foo v0.0.0 ([CWD])
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+}