Fix #612: main-repository aliases dropped under --useCquery

src/bazel.rs

@@ -1552,7 +1552,14 @@ impl BazelOptions {
     if "IncompatiblePlatformProvider" not in providers(target):
         target_repr = repr(target)
         if "<alias target" in target_repr:
-            return target_repr.split(" ")[2]
+            # repr() prints a main-repository alias with its apparent label
+            # (`//:tool`) even under --consistent_labels, while every other
+            # target is canonical (`@@//:tool`). Normalize so the alias
+            # matches the label it is later looked up by.
+            label = target_repr.split(" ")[2]
+            if label.startswith("//"):
+                label = "@@" + label
+            return label
         return str(target.label)
     return ""
 "#,

tests/e2e/regressions.rs

@@ -1259,3 +1259,84 @@ fn serve_rejects_packages_the_revision_does_not_track() {
         assert!(labels.is_superset(&expected_after_deletion()), "{labels:?}");
     }
 }
+
+/// Control for <https://github.com/Tinder/bazel-diff/issues/612>: in query mode a change
+/// behind a main-repository `alias` reaches the target that uses the alias.
+#[test]
+fn main_repo_alias_change_reaches_consumer_query() {
+    let first = copy_workspace("cquery_main_repo_alias");
+    let second = copy_workspace("cquery_main_repo_alias");
+    fs::write(second.path().join("bar/baz.txt"), "after\n").unwrap();
+    let impacted = diff_workspaces(first.path(), second.path(), &[]);
+    for name in ["//bar:baz.txt", "//bar:baz", "//:tool", "//:wrapper"] {
+        assert!(
+            impacted
+                .iter()
+                .any(|label| label == name || label.trim_start_matches("@@") == name),
+            "{name} should be impacted through the alias, got {impacted:?}"
+        );
+    }
+}
+
+/// Reproducer for <https://github.com/Tinder/bazel-diff/issues/612>: under `--useCquery`
+/// the compatible-target cquery names a main-repository alias by `repr(target)`, which
+/// Bazel prints with its apparent label (`//:tool`) even under `--consistent_labels`,
+/// while the target itself is named canonically (`@@//:tool`). The two never match, so
+/// the alias is filtered out as if it were platform-incompatible and takes its edges with
+/// it: `//:wrapper` has no node for `//:tool` to depend on and is never impacted.
+#[test]
+fn main_repo_alias_change_reaches_consumer_cquery() {
+    let first = copy_workspace("cquery_main_repo_alias");
+    let second = copy_workspace("cquery_main_repo_alias");
+    fs::write(second.path().join("bar/baz.txt"), "after\n").unwrap();
+
+    let output = tempfile::tempdir().unwrap();
+    let from = output.path().join("from.json");
+    let to = output.path().join("to.json");
+    let edges_file = output.path().join("edges.json");
+    let result = output.path().join("impacted.txt");
+    assert!(generate(first.path(), &from, &["--useCquery"])
+        .status
+        .success());
+    assert!(generate(
+        second.path(),
+        &to,
+        &[
+            "--useCquery",
+            "--depEdgesFile",
+            edges_file.to_str().unwrap()
+        ],
+    )
+    .status
+    .success());
+    assert!(impacted(second.path(), &from, &to, &result, &[])
+        .status
+        .success());
+
+    let hashes = hashes(&to);
+    assert!(
+        hashes.keys().any(|label| label.ends_with("//:tool")),
+        "the alias //:tool was dropped from the cquery hashes: {:?}",
+        hashes.keys().collect::<Vec<_>>()
+    );
+    let edges = dep_edges(&edges_file);
+    let wrapper_edges = edges
+        .iter()
+        .find(|(label, _)| label.ends_with("//:wrapper"))
+        .map(|(_, deps)| deps.clone())
+        .expect("//:wrapper has dep edges");
+    assert!(
+        wrapper_edges.iter().any(|dep| dep.ends_with("//:tool")),
+        "//:wrapper lost its edge to the alias //:tool: {wrapper_edges:?}"
+    );
+
+    let impacted = read_lines(&result);
+    for name in ["//bar:baz.txt", "//bar:baz", "//:tool", "//:wrapper"] {
+        assert!(
+            impacted
+                .iter()
+                .any(|label| label == name || label.trim_start_matches("@@") == name),
+            "{name} should be impacted through the alias under cquery, got {impacted:?}"
+        );
+    }
+}

tests/resources/workspaces/cquery_main_repo_alias/BUILD.bazel

@@ -0,0 +1,14 @@
+# A main-repository alias in front of the file that changes. `//:wrapper`
+# reaches `bar/baz.txt` only through the alias, so it must be impacted when
+# the file changes.
+alias(
+    name = "tool",
+    actual = "//bar:baz",
+)
+
+genrule(
+    name = "wrapper",
+    srcs = [":tool"],
+    outs = ["wrapper.txt"],
+    cmd = "cat $(SRCS) > $@",
+)

tests/resources/workspaces/cquery_main_repo_alias/MODULE.bazel

@@ -0,0 +1,4 @@
+module(
+    name = "cquery_main_repo_alias",
+    version = "0.0.0",
+)

tests/resources/workspaces/cquery_main_repo_alias/README.md

@@ -0,0 +1,25 @@
+# Main-repository alias under cquery
+
+Reproduces [GitHub Issue #612](https://github.com/Tinder/bazel-diff/issues/612):
+with `--useCquery`, a target that reaches its inputs through a main-repository
+`alias` stops seeing changes to them.
+
+## The graph
+
+`//:wrapper` (a `genrule`) lists `//:tool` in its `srcs`. `//:tool` is an
+`alias` of `//bar:baz`, a `filegroup` over `bar/baz.txt`.
+
+## Expected behaviour
+
+Changing `bar/baz.txt` impacts `//bar:baz.txt`, `//bar:baz`, `//:tool`,
+`//:wrapper` and `//:wrapper.txt`, in query mode and in cquery mode alike.
+
+## Behaviour before the fix
+
+The compatible-target cquery that filters out `IncompatiblePlatformProvider`
+targets names an alias by `repr(target)`, and Bazel prints a main-repository
+alias with its apparent label (`//:tool`) even under `--consistent_labels`,
+while every other target is canonical (`@@//:tool`). The two never match, so
+the alias is dropped as if it were incompatible, and with it every edge from
+`//:wrapper` through it. Under cquery only `@@//bar:baz` and `@@//bar:baz.txt`
+are reported as impacted.

tests/resources/workspaces/cquery_main_repo_alias/bar/BUILD.bazel

@@ -0,0 +1,5 @@
+filegroup(
+    name = "baz",
+    srcs = ["baz.txt"],
+    visibility = ["//visibility:public"],
+)

tests/resources/workspaces/cquery_main_repo_alias/bar/baz.txt

@@ -0,0 +1 @@
+before

tools/e2e/rust_e2e_cases.bzl

@@ -223,6 +223,14 @@ RUST_E2E_SUITES = [
                 "name": "regressions::macro_bzl_change_impacts_callers",
                 "timeout": "moderate",
             },
+            {
+                "name": "regressions::main_repo_alias_change_reaches_consumer_cquery",
+                "timeout": "moderate",
+            },
+            {
+                "name": "regressions::main_repo_alias_change_reaches_consumer_query",
+                "timeout": "moderate",
+            },
             {
                 "name": "regressions::module_comment_and_lock_reformat_are_noops",
                 "timeout": "moderate",