Marking Cargo.lock as generated

src/cargo/ops/lockfile.rs

@@ -43,13 +43,32 @@ pub fn write_pkg_lockfile(ws: &Workspace<'_>, resolve: &Resolve) -> CargoResult<
 
     let mut out = String::new();
 
-    // Preserve the top comments in the lockfile
-    // This is in preparation for marking it as generated
-    // https://github.com/rust-lang/cargo/issues/6180
+    // At the start of the file we notify the reader that the file is generated.
+    // Specifically Phabricator ignores files containing "@generated", so we use that.
+    let marker_line = "# This file is automatically @generated by Cargo.";
+    let extra_line = "# It is not intended for manual editing.";
+    out.push_str(marker_line);
+    out.push('\n');
+    out.push_str(extra_line);
+    out.push('\n');
+    // and preserve any other top comments
     if let Ok(orig) = &orig {
-        for line in orig.lines().take_while(|line| line.starts_with('#')) {
-            out.push_str(line);
-            out.push_str("\n");
+        let mut comments = orig.lines().take_while(|line| line.starts_with('#'));
+        if let Some(first) = comments.next() {
+            if first != marker_line {
+                out.push_str(first);
+                out.push('\n');
+            }
+            if let Some(second) = comments.next() {
+                if second != extra_line {
+                    out.push_str(second);
+                    out.push('\n');
+                }
+                for line in comments {
+                    out.push_str(line);
+                    out.push('\n');
+                }
+            }
         }
     }
 

tests/testsuite/generate_lockfile.rs

@@ -144,7 +144,7 @@ fn preserve_line_endings_issue_2076() {
 
     let lock0 = p.read_lockfile();
 
-    assert!(lock0.starts_with("[[package]]\n"));
+    assert!(lock0.starts_with("# This file is automatically @generated by Cargo.\n# It is not intended for manual editing.\n"));
 
     let lock1 = lock0.replace("\n", "\r\n");
     {
@@ -158,7 +158,7 @@ fn preserve_line_endings_issue_2076() {
 
     let lock2 = p.read_lockfile();
 
-    assert!(lock2.starts_with("[[package]]\r\n"));
+    assert!(lock2.starts_with("# This file is automatically @generated by Cargo.\r\n# It is not intended for manual editing.\r\n"));
     assert_eq!(lock1, lock2);
 }
 

tests/testsuite/lockfile_compat.rs

@@ -13,7 +13,9 @@ fn oldest_lockfile_still_works() {
 fn oldest_lockfile_still_works_with_command(cargo_command: &str) {
     Package::new("bar", "0.1.0").publish();
 
-    let expected_lockfile = r#"[[package]]
+    let expected_lockfile = r#"# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
 name = "bar"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -29,7 +31,8 @@ dependencies = [
 "checksum bar 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "[..]"
 "#;
 
-    let old_lockfile = r#"[root]
+    let old_lockfile = r#"
+[root]
 name = "foo"
 version = "0.0.1"
 dependencies = [
@@ -165,6 +168,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
     let lock = p.read_lockfile();
     assert!(lock.starts_with(
         r#"
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
 [[package]]
 name = "bar"
 version = "0.1.0"
@@ -404,6 +409,7 @@ fn current_lockfile_format() {
     let actual = p.read_lockfile();
 
     let expected = "\
+# This file is automatically @generated by Cargo.\n# It is not intended for manual editing.
 [[package]]
 name = \"bar\"
 version = \"0.1.0\"
@@ -430,7 +436,10 @@ dependencies = [
 fn lockfile_without_root() {
     Package::new("bar", "0.1.0").publish();
 
-    let lockfile = r#"[[package]]
+    let lockfile = r#"
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
 name = "bar"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"

tests/testsuite/update.rs

@@ -401,19 +401,23 @@ fn preserve_top_comment() {
 
     p.cargo("update").run();
 
-    let mut lockfile = p.read_file("Cargo.lock");
-    lockfile.insert_str(0, "# @generated\n");
-    lockfile.insert_str(0, "# some other comment\n");
+    let lockfile = p.read_lockfile();
+    assert!(lockfile.starts_with("# This file is automatically @generated by Cargo.\n# It is not intended for manual editing.\n"));
+
+    let mut lines = lockfile.lines().collect::<Vec<_>>();
+    lines.insert(2, "# some other comment");
+    let mut lockfile = lines.join("\n");
+    lockfile.push_str("\n"); // .lines/.join loses the last newline
     println!("saving Cargo.lock contents:\n{}", lockfile);
 
     p.change_file("Cargo.lock", &lockfile);
 
     p.cargo("update").run();
 
-    let lockfile2 = p.read_file("Cargo.lock");
+    let lockfile2 = p.read_lockfile();
     println!("loaded Cargo.lock contents:\n{}", lockfile2);
 
-    assert!(lockfile == lockfile2);
+    assert_eq!(lockfile, lockfile2);
 }
 
 #[test]