Auto merge of #13505 - epage:edition-warn, r=weihanglo

feat(toml): Warn on unset Edition

### What does this PR try to resolve?

On [Internals](https://internals.rust-lang.org/t/idea-rustc-cargo-should-warn-on-unspecified-edition/20309), the idea came up for warning on unset Edition.

Besides helping people who forget to set the Edition, this creates symmetry between `Cargo.toml` and cargo scripts (#12207).  While the default is different in each case, we are making the default obvious and guiding people away from it.

### How should we test and review this PR?

There are separate commits for adding tests (and refactors) so the changes in behavior will be more obvious

### Additional information

This builds on
- #13499
- #13504

10 files changed, 200 insertions, 25 deletions

diff --git a/src/cargo/core/features.rs b/src/cargo/core/features.rs
index f0cd9c48d..76ccdadb6 100644
--- a/src/cargo/core/features.rs
+++ b/src/cargo/core/features.rs
@@ -180,9 +180,12 @@ pub type AllowFeatures = BTreeSet<String>;
 /// [`is_stable`]: Edition::is_stable
 /// [`toml::to_real_manifest`]: crate::util::toml::to_real_manifest
 /// [`features!`]: macro.features.html
-#[derive(Clone, Copy, Debug, Hash, PartialOrd, Ord, Eq, PartialEq, Serialize, Deserialize)]
+#[derive(
+    Default, Clone, Copy, Debug, Hash, PartialOrd, Ord, Eq, PartialEq, Serialize, Deserialize,
+)]
 pub enum Edition {
     /// The 2015 edition
+    #[default]
     Edition2015,
     /// The 2018 edition
     Edition2018,
@@ -199,6 +202,12 @@ impl Edition {
     pub const LATEST_UNSTABLE: Option<Edition> = Some(Edition::Edition2024);
     /// The latest stable edition.
     pub const LATEST_STABLE: Edition = Edition::Edition2021;
+    pub const ALL: &'static [Edition] = &[
+        Self::Edition2015,
+        Self::Edition2018,
+        Self::Edition2021,
+        Self::Edition2024,
+    ];
     /// Possible values allowed for the `--edition` CLI flag.
     ///
     /// This requires a static value due to the way clap works, otherwise I
diff --git a/src/cargo/util/toml/mod.rs b/src/cargo/util/toml/mod.rs
index 8049f538c..1f10d37d3 100644
--- a/src/cargo/util/toml/mod.rs
+++ b/src/cargo/util/toml/mod.rs
@@ -9,6 +9,7 @@ use crate::AlreadyPrintedError;
 use anyhow::{anyhow, bail, Context as _};
 use cargo_platform::Platform;
 use cargo_util::paths;
+use cargo_util_schemas::core::PartialVersion;
 use cargo_util_schemas::manifest;
 use cargo_util_schemas::manifest::RustVersion;
 use itertools::Itertools;
@@ -563,14 +564,69 @@ pub fn to_real_manifest(
         source_id,
     );
 
+    let rust_version = if let Some(rust_version) = &package.rust_version {
+        let rust_version = field_inherit_with(rust_version.clone(), "rust_version", || {
+            inherit()?.rust_version()
+        })?;
+        Some(rust_version)
+    } else {
+        None
+    };
+
     let edition = if let Some(edition) = package.edition.clone() {
         let edition: Edition = field_inherit_with(edition, "edition", || inherit()?.edition())?
             .parse()
             .with_context(|| "failed to parse the `edition` key")?;
         package.edition = Some(manifest::InheritableField::Value(edition.to_string()));
+        if let Some(rust_version) = &rust_version {
+            let req = rust_version.to_caret_req();
+            if let Some(first_version) = edition.first_version() {
+                let unsupported =
+                    semver::Version::new(first_version.major, first_version.minor - 1, 9999);
+                if req.matches(&unsupported) {
+                    bail!(
+                        "rust-version {} is older than first version ({}) required by \
+                            the specified edition ({})",
+                        rust_version,
+                        first_version,
+                        edition,
+                    )
+                }
+            }
+        }
         edition
     } else {
-        Edition::Edition2015
+        let msrv_edition = if let Some(rust_version) = &rust_version {
+            Edition::ALL
+                .iter()
+                .filter(|e| {
+                    e.first_version()
+                        .map(|e| {
+                            let e = PartialVersion::from(e);
+                            e <= **rust_version
+                        })
+                        .unwrap_or_default()
+                })
+                .max()
+                .copied()
+        } else {
+            None
+        }
+        .unwrap_or_default();
+        let default_edition = Edition::default();
+        let latest_edition = Edition::LATEST_STABLE;
+
+        let tip = if msrv_edition == default_edition {
+            String::new()
+        } else if msrv_edition == latest_edition {
+            format!(" while the latest is {latest_edition}")
+        } else {
+            format!(" while {msrv_edition} is compatible with `rust-version`")
+        };
+        warnings.push(format!(
+            "no edition set: defaulting to the {default_edition} edition{tip}",
+        ));
+        default_edition
     };
     // Add these lines if start a new unstable edition.
     // ```
@@ -588,29 +644,6 @@ pub fn to_real_manifest(
         )));
     }
 
-    let rust_version = if let Some(rust_version) = &package.rust_version {
-        let rust_version = field_inherit_with(rust_version.clone(), "rust_version", || {
-            inherit()?.rust_version()
-        })?;
-        let req = rust_version.to_caret_req();
-        if let Some(first_version) = edition.first_version() {
-            let unsupported =
-                semver::Version::new(first_version.major, first_version.minor - 1, 9999);
-            if req.matches(&unsupported) {
-                bail!(
-                    "rust-version {} is older than first version ({}) required by \
-                            the specified edition ({})",
-                    rust_version,
-                    first_version,
-                    edition,
-                )
-            }
-        }
-        Some(rust_version)
-    } else {
-        None
-    };
-
     if package.metabuild.is_some() {
         features.require(Feature::metabuild())?;
     }
diff --git a/tests/testsuite/bench.rs b/tests/testsuite/bench.rs
index 9e5cc1b17..35c78454a 100644
--- a/tests/testsuite/bench.rs
+++ b/tests/testsuite/bench.rs
@@ -331,6 +331,7 @@ fn bench_with_lib_dep() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [[bin]]
@@ -396,6 +397,7 @@ fn bench_with_deep_lib_dep() {
                 [package]
                 name = "bar"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [dependencies.foo]
@@ -454,6 +456,7 @@ fn external_bench_explicit() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [[bench]]
@@ -697,6 +700,7 @@ fn lib_bin_same_name() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [lib]
@@ -796,6 +800,7 @@ fn lib_with_standard_name2() {
                 [package]
                 name = "syntax"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [lib]
@@ -842,6 +847,7 @@ fn bench_dylib() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [lib]
@@ -883,6 +889,7 @@ fn bench_dylib() {
                 [package]
                 name = "bar"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [lib]
@@ -932,6 +939,7 @@ fn bench_twice_with_build_cmd() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
                 build = "build.rs"
             "#,
@@ -977,6 +985,7 @@ fn bench_with_examples() {
                 [package]
                 name = "foo"
                 version = "6.6.6"
+                edition = "2015"
                 authors = []
 
                 [[example]]
@@ -1061,6 +1070,7 @@ fn test_a_bench() {
                 name = "foo"
                 authors = []
                 version = "0.1.0"
+                edition = "2015"
 
                 [lib]
                 name = "foo"
@@ -1219,6 +1229,7 @@ fn test_bench_multiple_packages() {
                 name = "foo"
                 authors = []
                 version = "0.1.0"
+                edition = "2015"
 
                 [dependencies.bar]
                 path = "../bar"
@@ -1239,6 +1250,7 @@ fn test_bench_multiple_packages() {
                 name = "bar"
                 authors = []
                 version = "0.1.0"
+                edition = "2015"
 
                 [[bench]]
                 name = "bbar"
@@ -1269,6 +1281,7 @@ fn test_bench_multiple_packages() {
                 name = "baz"
                 authors = []
                 version = "0.1.0"
+                edition = "2015"
 
                 [[bench]]
                 name = "bbaz"
@@ -1307,6 +1320,7 @@ fn bench_all_workspace() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [dependencies]
                 bar = { path = "bar" }
@@ -1360,6 +1374,7 @@ fn bench_all_exclude() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [workspace]
                 members = ["bar", "baz"]
@@ -1405,6 +1420,7 @@ fn bench_all_exclude_glob() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [workspace]
                 members = ["bar", "baz"]
@@ -1549,6 +1565,7 @@ fn legacy_bench_name() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [[bench]]
                 name = "bench"
diff --git a/tests/testsuite/check_cfg.rs b/tests/testsuite/check_cfg.rs
index 3f96451e0..004fc482a 100644
--- a/tests/testsuite/check_cfg.rs
+++ b/tests/testsuite/check_cfg.rs
@@ -38,6 +38,7 @@ fn features() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [features]
                 f_a = []
@@ -63,6 +64,7 @@ fn features_with_deps() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [dependencies]
                 bar = { path = "bar/" }
@@ -93,6 +95,7 @@ fn features_with_opt_deps() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [dependencies]
                 bar = { path = "bar/", optional = true }
@@ -124,6 +127,7 @@ fn features_with_namespaced_features() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [dependencies]
                 bar = { path = "bar/", optional = true }
@@ -154,6 +158,7 @@ fn features_fingerprint() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [features]
                 f_a = []
@@ -181,6 +186,7 @@ fn features_fingerprint() {
             [package]
             name = "foo"
             version = "0.1.0"
+            edition = "2015"
 
             [features]
             f_b = []
@@ -199,6 +205,7 @@ fn features_fingerprint() {
             [package]
             name = "foo"
             version = "0.1.0"
+            edition = "2015"
 
             [features]
             f_a = []
@@ -239,6 +246,7 @@ fn features_test() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [features]
                 f_a = []
@@ -264,6 +272,7 @@ fn features_doctest() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [features]
                 default = ["f_a"]
@@ -322,6 +331,7 @@ fn features_doc() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [features]
                 default = ["f_a"]
@@ -348,6 +358,7 @@ fn build_script_feedback() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
                 build = "build.rs"
             "#,
@@ -375,6 +386,7 @@ fn build_script_doc() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
                 build = "build.rs"
             "#,
@@ -415,6 +427,7 @@ fn build_script_override() {
                 [package]
                 name = "foo"
                 version = "0.5.0"
+                edition = "2015"
                 authors = []
                 links = "a"
                 build = "build.rs"
@@ -453,6 +466,7 @@ fn build_script_override_feature_gate() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
                 links = "a"
             "#,
         )
@@ -484,6 +498,7 @@ fn build_script_test() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
                 build = "build.rs"
             "#,
@@ -539,6 +554,7 @@ fn build_script_feature_gate() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 build = "build.rs"
             "#,
         )
@@ -567,6 +583,7 @@ fn config_valid() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [features]
                 f_a = []
@@ -599,6 +616,7 @@ fn config_invalid() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
             "#,
         )
         .file("src/main.rs", "fn main() {}")
@@ -627,6 +645,7 @@ fn config_feature_gate() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [features]
                 f_a = []
diff --git a/tests/testsuite/custom_target.rs b/tests/testsuite/custom_target.rs
index 518b19672..191d4cd51 100644
--- a/tests/testsuite/custom_target.rs
+++ b/tests/testsuite/custom_target.rs
@@ -72,6 +72,7 @@ fn custom_target_dependency() {
 
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = ["author@example.com"]
 
                 [dependencies]
@@ -189,6 +190,7 @@ fn changing_spec_relearns_crate_types() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [lib]
                 crate-type = ["cdylib"]
diff --git a/tests/testsuite/docscrape.rs b/tests/testsuite/docscrape.rs
index 0d96ad718..7398ee0a3 100644
--- a/tests/testsuite/docscrape.rs
+++ b/tests/testsuite/docscrape.rs
@@ -11,6 +11,7 @@ fn basic() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
             "#,
         )
@@ -83,6 +84,7 @@ fn main() {
                 [package]
                 name = "a"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
         "#,
         )
@@ -136,6 +138,7 @@ fn avoid_build_script_cycle() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
                 links = "foo"
 
@@ -155,6 +158,7 @@ fn avoid_build_script_cycle() {
                 [package]
                 name = "bar"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
                 links = "bar"
             "#,
@@ -177,6 +181,7 @@ fn complex_reverse_dependencies() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [dev-dependencies]
@@ -195,6 +200,7 @@ fn complex_reverse_dependencies() {
                 [package]
                 name = "a"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [lib]
@@ -214,6 +220,7 @@ fn complex_reverse_dependencies() {
                 [package]
                 name = "b"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
             "#,
         )
@@ -234,6 +241,7 @@ fn crate_with_dash() {
                 [package]
                 name = "da-sh"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
             "#,
         )
@@ -258,6 +266,7 @@ fn configure_target() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [lib]
@@ -305,6 +314,7 @@ fn configure_profile_issue_10500() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
 
                 [profile.dev]
@@ -379,6 +389,7 @@ fn cache() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
             "#,
         )
@@ -419,6 +430,7 @@ fn no_fail_bad_lib() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
             "#,
         )
@@ -463,6 +475,7 @@ fn fail_bad_build_script() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
             "#,
         )
         .file("src/lib.rs", "")
@@ -493,6 +506,7 @@ fn no_fail_bad_example() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
                 authors = []
             "#,
         )
@@ -560,6 +574,7 @@ fn no_scrape_with_dev_deps() {
             [package]
             name = "foo"
             version = "0.0.1"
+            edition = "2015"
             authors = []
 
             [dev-dependencies]
@@ -574,6 +589,7 @@ fn no_scrape_with_dev_deps() {
             [package]
             name = "a"
             version = "0.0.1"
+            edition = "2015"
             authors = []
         "#,
         )
@@ -622,6 +638,7 @@ fn use_dev_deps_if_explicitly_enabled() {
             [package]
             name = "foo"
             version = "0.0.1"
+            edition = "2015"
             authors = []
 
             [[example]]
@@ -640,6 +657,7 @@ fn use_dev_deps_if_explicitly_enabled() {
             [package]
             name = "a"
             version = "0.0.1"
+            edition = "2015"
             authors = []
         "#,
         )
@@ -673,6 +691,7 @@ fn only_scrape_documented_targets() {
             [package]
             name = "bar"
             version = "0.0.1"
+            edition = "2015"
             authors = []            
 
             [lib]
@@ -694,6 +713,7 @@ fn only_scrape_documented_targets() {
             [package]
             name = "foo"
             version = "0.0.1"
+            edition = "2015"
             authors = []      
         "#,
         )
diff --git a/tests/testsuite/edition.rs b/tests/testsuite/edition.rs
index 377a86ec0..6f68233c1 100644
--- a/tests/testsuite/edition.rs
+++ b/tests/testsuite/edition.rs
@@ -122,3 +122,57 @@ fn edition_unstable() {
         )
         .run();
 }
+
+#[cargo_test]
+fn unset_edition_works_with_no_newer_compatible_edition() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = 'foo'
+                version = '0.1.0'
+                rust-version = "1.0"
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("check -v")
+        .with_stderr(
+            "\
+[WARNING] no edition set: defaulting to the 2015 edition
+[CHECKING] foo [..]
+[RUNNING] `rustc [..] --edition=2015 [..]`
+[FINISHED] [..]
+",
+        )
+        .run();
+}
+
+#[cargo_test]
+fn unset_edition_works_on_old_msrv() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = 'foo'
+                version = '0.1.0'
+                rust-version = "1.50"  # contains 2018 edition
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("check -v")
+        .with_stderr(
+            "\
+[WARNING] no edition set: defaulting to the 2015 edition while 2018 is compatible with `rust-version`
+[CHECKING] foo [..]
+[RUNNING] `rustc [..] --edition=2015 [..]`
+[FINISHED] [..]
+",
+        )
+        .run();
+}
diff --git a/tests/testsuite/https.rs b/tests/testsuite/https.rs
index c7aec9111..85a894a31 100644
--- a/tests/testsuite/https.rs
+++ b/tests/testsuite/https.rs
@@ -20,6 +20,7 @@ fn self_signed_should_fail() {
                     [package]
                     name = "foo"
                     version = "0.1.0"
+                    edition = "2015"
 
                     [dependencies]
                     bar = {{ git = "{url}" }}
@@ -106,6 +107,7 @@ fn self_signed_with_cacert() {
                     [package]
                     name = "foo"
                     version = "0.1.0"
+                    edition = "2015"
 
                     [dependencies]
                     bar = {{ git = "{url}" }}
@@ -139,6 +141,7 @@ fn github_works() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [dependencies]
                 bitflags = { git = "https://github.com/rust-lang/bitflags.git", tag="1.3.2" }
diff --git a/tests/testsuite/profile_trim_paths.rs b/tests/testsuite/profile_trim_paths.rs
index 67a7785fe..2cb266bf8 100644
--- a/tests/testsuite/profile_trim_paths.rs
+++ b/tests/testsuite/profile_trim_paths.rs
@@ -15,6 +15,7 @@ fn gated_manifest() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [profile.dev]
                 trim-paths = "macro"
@@ -71,6 +72,7 @@ fn release_profile_default_to_object() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
            "#,
         )
         .file("src/lib.rs", "")
@@ -101,6 +103,7 @@ fn one_option() {
                     [package]
                     name = "foo"
                     version = "0.0.1"
+                    edition = "2015"
 
                     [profile.dev]
                     trim-paths = "{option}"
@@ -143,6 +146,7 @@ fn multiple_options() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [profile.dev]
                 trim-paths = ["diagnostics", "macro", "object"]
@@ -174,6 +178,7 @@ fn profile_merge_works() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [profile.dev]
                 trim-paths = ["macro"]
@@ -213,6 +218,7 @@ fn registry_dependency() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [dependencies]
                 bar = "0.0.1"
@@ -268,6 +274,7 @@ fn git_dependency() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [dependencies]
                 bar = {{ git = "{url}" }}
@@ -314,6 +321,7 @@ fn path_dependency() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [dependencies]
                 bar = { path = "cocktail-bar" }
@@ -368,6 +376,7 @@ fn path_dependency_outside_workspace() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [dependencies]
                 bar = { path = "../bar" }
@@ -413,6 +422,7 @@ fn diagnostics_works() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [dependencies]
                 bar = "0.0.1"
@@ -532,6 +542,7 @@ fn object_works_helper(split_debuginfo: &str, run: impl Fn(&std::path::Path) ->
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [dependencies]
                 bar = "0.0.1"
@@ -635,6 +646,7 @@ fn custom_build_env_var_trim_paths() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
            "#,
         )
         .file("src/lib.rs", "")
@@ -664,6 +676,7 @@ fn custom_build_env_var_trim_paths() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [profile.dev]
                 trim-paths = {opts}
@@ -722,6 +735,7 @@ fn lldb_works_after_trimmed() {
                 [package]
                 name = "foo"
                 version = "0.0.1"
+                edition = "2015"
 
                 [profile.dev]
                 trim-paths = "object"
diff --git a/tests/testsuite/ssh.rs b/tests/testsuite/ssh.rs
index f8c12819b..66ec55d53 100644
--- a/tests/testsuite/ssh.rs
+++ b/tests/testsuite/ssh.rs
@@ -110,6 +110,7 @@ fn foo_bar_project(url: &str) -> Project {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [dependencies]
                 bar = {{ git = "{url}" }}
@@ -406,6 +407,7 @@ fn invalid_github_key() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [dependencies]
                 bitflags = { git = "ssh://git@github.com/rust-lang/bitflags.git", tag = "1.3.2" }
@@ -444,6 +446,7 @@ fn bundled_github_works() {
                 [package]
                 name = "foo"
                 version = "0.1.0"
+                edition = "2015"
 
                 [dependencies]
                 bitflags = { git = "ssh://git@github.com/rust-lang/bitflags.git", tag = "1.3.2" }
@@ -552,6 +555,7 @@ Caused by:
             [package]
             name = "foo"
             version = "0.1.0"
+            edition = "2015"
 
             [dependencies]
             bitflags = { git = "ssh://git@github.com:22/rust-lang/bitflags.git", tag = "1.3.2" }