Improved error message for versions prefixed with v

src/bin/cargo/commands/install.rs

@@ -286,6 +286,12 @@ fn parse_semver_flag(v: &str) -> CargoResult<VersionReq> {
         .next()
         .ok_or_else(|| format_err!("no version provided for the `--version` flag"))?;
 
+    if let Some(stripped) = v.strip_prefix("v") {
+        bail!(
+            "the version provided, `{v}` is not a valid SemVer requirement\n\n\
+            help: try changing the version to `{stripped}`",
+        )
+    }
     let is_req = "<>=^~".contains(first) || v.contains('*');
     if is_req {
         match v.parse::<VersionReq>() {

src/bin/cargo/commands/yank.rs

@@ -1,5 +1,6 @@
 use crate::command_prelude::*;
 
+use anyhow::Context;
 use cargo::ops;
 use cargo_credential::Secret;
 
@@ -60,5 +61,19 @@ fn resolve_crate<'k>(
         krate = Some(k);
         version = Some(v);
     }
+
+    if let Some(version) = version {
+        semver::Version::parse(version).with_context(|| {
+            if let Some(stripped) = version.strip_prefix("v") {
+                return format!(
+                    "the version provided, `{version}` is not a \
+                    valid SemVer version\n\n\
+                    help: try changing the version to `{stripped}`",
+                );
+            }
+            format!("invalid version `{version}`")
+        })?;
+    }
+
     Ok((krate, version))
 }

src/cargo/core/source_id.rs

@@ -523,8 +523,16 @@ impl SourceId {
         version: semver::Version,
         precise: &str,
     ) -> CargoResult<SourceId> {
-        let precise = semver::Version::parse(precise)
-            .with_context(|| format!("invalid version format for precise version `{precise}`"))?;
+        let precise = semver::Version::parse(precise).with_context(|| {
+            if let Some(stripped) = precise.strip_prefix("v") {
+                return format!(
+                    "the version provided, `{precise}` is not a \
+                    valid SemVer version\n\n\
+                    help: try changing the version to `{stripped}`",
+                );
+            }
+            format!("invalid version format for precise version `{precise}`")
+        })?;
 
         Ok(SourceId::wrap(SourceIdInner {
             precise: Some(Precise::Updated {

src/cargo/ops/cargo_add/crate_spec.rs

@@ -47,8 +47,16 @@ impl CrateSpec {
         package_name?;
 
         if let Some(version) = version {
-            semver::VersionReq::parse(version)
-                .with_context(|| format!("invalid version requirement `{version}`"))?;
+            semver::VersionReq::parse(version).with_context(|| {
+                if let Some(stripped) = version.strip_prefix("v") {
+                    return format!(
+                        "the version provided, `{version}` is not a \
+                         valid SemVer requirement\n\n\
+                         help: changing the package to `{name}@{stripped}`",
+                    );
+                }
+                format!("invalid version requirement `{version}`")
+            })?;
         }
 
         let id = Self {

tests/testsuite/cargo_add/mod.rs

@@ -126,6 +126,7 @@ mod path_base_unstable;
 mod path_dev;
 mod path_inferred_name;
 mod path_inferred_name_conflicts_full_feature;
+mod prefixed_v_in_version;
 mod preserve_dep_std_table;
 mod preserve_features_sorted;
 mod preserve_features_table;

tests/testsuite/cargo_add/prefixed_v_in_version/in

@@ -0,0 +1 @@
+../add-basic.in

tests/testsuite/cargo_add/prefixed_v_in_version/mod.rs

@@ -0,0 +1,26 @@
+use cargo_test_support::compare::assert_ui;
+use cargo_test_support::current_dir;
+use cargo_test_support::file;
+use cargo_test_support::prelude::*;
+use cargo_test_support::str;
+use cargo_test_support::Project;
+
+#[cargo_test]
+fn case() {
+    cargo_test_support::registry::init();
+
+    let project = Project::from_template(current_dir!().join("in"));
+    let project_root = project.root();
+    let cwd = &project_root;
+
+    snapbox::cmd::Command::cargo_ui()
+        .arg("add")
+        .arg_line("[email protected]")
+        .current_dir(cwd)
+        .assert()
+        .code(101)
+        .stdout_eq(str![""])
+        .stderr_eq(file!["stderr.term.svg"]);
+
+    assert_ui().subset_matches(current_dir!().join("out"), &project_root);
+}

tests/testsuite/cargo_add/prefixed_v_in_version/out/Cargo.toml

@@ -0,0 +1,6 @@
+[workspace]
+
+[package]
+name = "cargo-list-test-fixture"
+version = "0.0.0"
+edition = "2015"

tests/testsuite/install.rs

@@ -2899,3 +2899,19 @@ fn dry_run_remove_orphan() {
     // Ensure server is still installed after the dry run
     assert_has_installed_exe(paths::cargo_home(), "server");
 }
+
+#[cargo_test]
+fn prefixed_v_in_version() {
+    pkg("foo", "0.0.1");
+    cargo_process("install [email protected]")
+        .with_status(1)
+        .with_stderr_data(str![[r#"
+[ERROR] invalid value '[email protected]' for '[CRATE[@<VER>]]...': the version provided, `v0.0.1` is not a valid SemVer requirement
+
+[HELP] try changing the version to `0.0.1`
+
+For more information, try '--help'.
+
+"#]])
+        .run();
+}

tests/testsuite/update.rs

@@ -2709,3 +2709,41 @@ fn update_breaking_pre_release_upgrade() {
 "#]])
         .run();
 }
+
+#[cargo_test]
+fn prefixed_v_in_version() {
+    Package::new("bar", "1.0.0").publish();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+        [package]
+        name  =  "foo"
+        version  =  "0.0.1"
+        edition  =  "2015"
+        authors  =  []
+
+        [dependencies]
+        bar = "1.0.0"
+    "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("generate-lockfile").run();
+
+    Package::new("bar", "1.0.1").publish();
+    p.cargo("update bar --precise v1.0.1")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] the version provided, `v1.0.1` is not a valid SemVer version
+
+[HELP] try changing the version to `1.0.1`
+
+Caused by:
+  unexpected character 'v' while parsing major version number
+
+"#]])
+        .run();
+}

tests/testsuite/yank.rs

@@ -212,3 +212,71 @@ fn inline_and_explicit_version() {
 "#]])
         .run();
 }
+
+#[cargo_test]
+fn bad_version() {
+    let registry = registry::init();
+    setup("foo", "0.0.1");
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.0.1"
+                authors = []
+                license = "MIT"
+                description = "foo"
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("yank foo@bar")
+        .replace_crates_io(registry.index_url())
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] invalid version `bar`
+
+Caused by:
+  unexpected character 'b' while parsing major version number
+
+"#]])
+        .run();
+}
+
+#[cargo_test]
+fn prefixed_v_in_version() {
+    let registry = registry::init();
+    setup("foo", "0.0.1");
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.0.1"
+                authors = []
+                license = "MIT"
+                description = "foo"
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("yank [email protected]")
+        .replace_crates_io(registry.index_url())
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] the version provided, `v0.0.1` is not a valid SemVer version
+
+[HELP] try changing the version to `0.0.1`
+
+Caused by:
+  unexpected character 'v' while parsing major version number
+
+"#]])
+        .run();
+}