Don't error if in-diff contains multiple deletions (#220)

Fixes `Error: Patch input contains repeated filename: "/dev/null"` #219

NEWS.md

@@ -1,5 +1,9 @@
 # cargo-mutants changelog
 
+## Unreleased
+
+- Fixed: Fixed spurious "Patch input contains repeated filenames" error when `--in-diff` is given a patch that deletes multiple files.
+
 ## 23.12.2
 
 - New: A `--shard k/n` allows you to split the work across n independent parallel `cargo mutants` invocations running on separate machines to get a faster overall solution on large suites. You, or your CI system, are responsible for launching all the shards and checking whether any of them failed.

src/in_diff.rs

@@ -25,6 +25,10 @@ pub fn diff_filter(mutants: Vec<Mutant>, diff_text: &str) -> Result<Vec<Mutant>>
     let mut lines_changed_by_path: HashMap<&Utf8Path, Vec<usize>> = HashMap::new();
     for patch in &patches {
         let path = strip_patch_path(&patch.new.path);
+        if path == "/dev/null" {
+            // The file was deleted; we can't possibly match anything in it.
+            continue;
+        }
         if lines_changed_by_path
             .insert(path, affected_lines(patch))
             .is_some()

src/snapshots/cargo_mutants__visit__test__expected_mutants_for_own_source_tree.snap

@@ -181,6 +181,7 @@ src/fnvalue.rs: replace == with != in match_first_type_arg
 src/in_diff.rs: replace diff_filter -> Result<Vec<Mutant>> with Ok(vec![])
 src/in_diff.rs: replace diff_filter -> Result<Vec<Mutant>> with Ok(vec![Default::default()])
 src/in_diff.rs: replace diff_filter -> Result<Vec<Mutant>> with Err(::anyhow::anyhow!("mutated!"))
+src/in_diff.rs: replace == with != in diff_filter
 src/in_diff.rs: replace check_diff_new_text_matches -> Result<()> with Ok(())
 src/in_diff.rs: replace check_diff_new_text_matches -> Result<()> with Err(::anyhow::anyhow!("mutated!"))
 src/in_diff.rs: replace != with == in check_diff_new_text_matches

tests/cli/in_diff.rs

@@ -96,3 +96,42 @@ fn mismatched_diff_causes_error() {
             "Diff content doesn't match source file: src/lib.rs",
         ));
 }
+
+/// If the diff contains multiple deletions (with a new filename of /dev/null),
+/// don't fail.
+///
+/// <https://github.com/sourcefrog/cargo-mutants/issues/219>
+#[test]
+fn diff_with_multiple_deletions_is_ok() {
+    let diff = indoc! {r#"
+        diff --git a/src/monitor/collect.rs b/src/monitor/collect.rs
+        deleted file mode 100644
+        index d842cf9..0000000
+        --- a/src/monitor/collect.rs
+        +++ /dev/null
+        @@ -1,1 +0,0 @@
+        -// Some stuff
+        diff --git a/src/monitor/another.rs b/src/monitor/another.rs
+        deleted file mode 100644
+        index d842cf9..0000000
+        --- a/src/monitor/collect.rs
+        +++ /dev/null
+        @@ -1,1 +0,0 @@
+        -// More stuff
+    "#};
+    let mut diff_file = NamedTempFile::new().unwrap();
+    diff_file.write_all(diff.as_bytes()).unwrap();
+
+    let tmp = copy_of_testdata("diff1");
+
+    run()
+        .args(["mutants", "--no-shuffle", "-d"])
+        .arg(tmp.path())
+        .arg("--in-diff")
+        .arg(diff_file.path())
+        .assert()
+        .stderr(predicates::str::contains(
+            "No mutants found under the active filters",
+        ))
+        .success();
+}