copies-rust: add a macro-based unit-testing framework

`compare_values`, `merge_copies_dict`, and `CombineChangesetCopies`
are APIs whose signatures involve non-trivial types.
Calling them directly in unit tests would involve a lot of verbose
setup code that obscures the meaningful parts of a given test case.

This adds a macro-based test-harness with pseudo-syntax to tersely
create arguments and expected return values in the correct types.

For now there is only one (not particularly meaningful) test case
per tested function, just to exercize the macros.

Differential Revision: https://phab.mercurial-scm.org/D10071

rust/hg-core/src/copy_tracing/tests.rs

@@ -0,0 +1,141 b''
+use super::*;
+
+/// Unit tests for:
+///
+/// ```ignore
+/// fn compare_value(
+///     current_merge: Revision,
+///     merge_case_for_dest: impl Fn() -> MergeCase,
+///     src_minor: &CopySource,
+///     src_major: &CopySource,
+/// ) -> (MergePick, /* overwrite: */ bool)
+///  ```
+#[test]
+fn test_compare_value() {
+    // The `compare_value!` macro calls the `compare_value` function with
+    // arguments given in pseudo-syntax:
+    //
+    // * For `merge_case_for_dest` it takes a plain `MergeCase` value instead
+    //   of a closure.
+    // * `CopySource` values are represented as `(rev, path, overwritten)`
+    //   tuples of type `(Revision, Option<PathToken>, OrdSet<Revision>)`.
+    // * `PathToken` is an integer not read by `compare_value`. It only checks
+    //   for `Some(_)` indicating a file copy v.s. `None` for a file deletion.
+    // * `OrdSet<Revision>` is represented as a Python-like set literal.
+
+    use MergeCase::*;
+    use MergePick::*;
+
+    assert_eq!(
+        compare_value!(1, Normal, (1, None, { 1 }), (1, None, { 1 })),
+        (Any, false)
+    );
+}
+
+/// Unit tests for:
+///
+/// ```ignore
+/// fn merge_copies_dict(
+///     path_map: &TwoWayPathMap, // Not visible in test cases
+///     current_merge: Revision,
+///     minor: InternalPathCopies,
+///     major: InternalPathCopies,
+///     get_merge_case: impl Fn(&HgPath) -> MergeCase + Copy,
+/// ) -> InternalPathCopies
+/// ```
+#[test]
+fn test_merge_copies_dict() {
+    // The `merge_copies_dict!` macro calls the `merge_copies_dict` function
+    // with arguments given in pseudo-syntax:
+    //
+    // * `TwoWayPathMap` and path tokenization are implicitly taken care of.
+    //   All paths are given as string literals.
+    // * Key-value maps are represented with `{key1 => value1, key2 => value2}`
+    //   pseudo-syntax.
+    // * `InternalPathCopies` is a map of copy destination path keys to
+    //   `CopySource` values.
+    //   - `CopySource` is represented as a `(rev, source_path, overwritten)`
+    //     tuple of type `(Revision, Option<Path>, OrdSet<Revision>)`.
+    //   - Unlike in `test_compare_value`, source paths are string literals.
+    //   - `OrdSet<Revision>` is again represented as a Python-like set
+    //     literal.
+    // * `get_merge_case` is represented as a map of copy destination path to
+    //   `MergeCase`. The default for paths not in the map is
+    //   `MergeCase::Normal`.
+    //
+    // `internal_path_copies!` creates an `InternalPathCopies` value with the
+    // same pseudo-syntax as in `merge_copies_dict!`.
+
+    use MergeCase::*;
+
+    assert_eq!(
+        merge_copies_dict!(
+            1,
+            {"foo" => (1, None, {})},
+            {},
+            {"foo" => Merged}
+        ),
+        internal_path_copies!("foo" => (1, None, {}))
+    );
+}
+
+/// Unit tests for:
+///
+/// ```ignore
+/// impl CombineChangesetCopies {
+///     fn new(children_count: HashMap<Revision, usize>) -> Self
+///
+///     // Called repeatedly:
+///     fn add_revision_inner<'a>(
+///         &mut self,
+///         rev: Revision,
+///         p1: Revision,
+///         p2: Revision,
+///         copy_actions: impl Iterator<Item = Action<'a>>,
+///         get_merge_case: impl Fn(&HgPath) -> MergeCase + Copy,
+///     )
+///
+///     fn finish(mut self, target_rev: Revision) -> PathCopies
+/// }
+/// ```
+#[test]
+fn test_combine_changeset_copies() {
+    // `combine_changeset_copies!` creates a `CombineChangesetCopies` with
+    // `new`, then calls `add_revision_inner` repeatedly, then calls `finish`
+    // for its return value.
+    //
+    // All paths given as string literals.
+    //
+    // * Key-value maps are represented with `{key1 => value1, key2 => value2}`
+    //   pseudo-syntax.
+    // * `children_count` is a map of revision numbers to count of children in
+    //   the DAG. It includes all revisions that should be considered by the
+    //   algorithm.
+    // * Calls to `add_revision_inner` are represented as an array of anonymous
+    //   structs with named fields, one pseudo-struct per call.
+    //
+    // `path_copies!` creates a `PathCopies` value, a map of copy destination
+    // keys to copy source values. Note: the arrows for map literal syntax
+    // point **backwards** compared to the logical direction of copy!
+
+    use crate::NULL_REVISION as NULL;
+    use Action::*;
+    use MergeCase::*;
+
+    assert_eq!(
+        combine_changeset_copies!(
+            { 1 => 1, 2 => 1 },
+            [
+                { rev: 1, p1: NULL, p2: NULL, actions: [], merge_cases: {}, },
+                { rev: 2, p1: NULL, p2: NULL, actions: [], merge_cases: {}, },
+                {
+                    rev: 3, p1: 1, p2: 2,
+                    actions: [CopiedFromP1("destination.txt", "source.txt")],
+                    merge_cases: {"destination.txt" => Merged},
+                },
+            ],
+            3,
+        ),
+        path_copies!("destination.txt" => "source.txt")
+    );
+}

rust/hg-core/src/copy_tracing/tests_support.rs

@@ -0,0 +1,199 b''
+//! Supporting macros for `tests.rs` in the same directory.
+//! See comments there for usage.
+
+/// Python-like set literal
+macro_rules! set {
+    (
+        $Type: ty {
+            $( $value: expr ),* $(,)?
+        }
+    ) => {{
+        #[allow(unused_mut)]
+        let mut set = <$Type>::new();
+        $( set.insert($value); )*
+        set
+    }}
+}
+
+/// `{key => value}` map literal
+macro_rules! map {
+    (
+        $Type: ty {
+            $( $key: expr => $value: expr ),* $(,)?
+        }
+    ) => {{
+        #[allow(unused_mut)]
+        let mut set = <$Type>::new();
+        $( set.insert($key, $value); )*
+        set
+    }}
+}
+
+macro_rules! copy_source {
+    ($rev: expr, $path: expr, $overwritten: tt) => {
+        CopySource {
+            rev: $rev,
+            path: $path,
+            overwritten: set!(OrdSet<Revision> $overwritten),
+        }
+    };
+}
+
+macro_rules! compare_value {
+    (
+        $merge_revision: expr,
+        $merge_case_for_dest: ident,
+        ($min_rev: expr, $min_path: expr, $min_overwrite: tt),
+        ($maj_rev: expr, $maj_path: expr, $maj_overwrite: tt) $(,)?
+    ) => {
+        compare_value(
+            $merge_revision,
+            || $merge_case_for_dest,
+            &copy_source!($min_rev, $min_path, $min_overwrite),
+            &copy_source!($maj_rev, $maj_path, $maj_overwrite),
+        )
+    };
+}
+
+macro_rules! tokenized_path_copies {
+    (
+        $path_map: ident, {$(
+            $dest: expr => (
+                $src_rev: expr,
+                $src_path: expr,
+                $src_overwrite: tt
+            )
+        ),*}
+        $(,)*
+    ) => {
+        map!(InternalPathCopies {$(
+            $path_map.tokenize(HgPath::new($dest)) =>
+            copy_source!(
+                $src_rev,
+                Option::map($src_path, |p: &str| {
+                    $path_map.tokenize(HgPath::new(p))
+                }),
+                $src_overwrite
+            )
+        )*})
+    }
+}
+
+macro_rules! merge_case_callback {
+    (
+        $( $merge_path: expr => $merge_case: ident ),*
+        $(,)?
+    ) => {
+        #[allow(unused)]
+        |merge_path| -> MergeCase {
+            $(
+                if (merge_path == HgPath::new($merge_path)) {
+                    return $merge_case
+                }
+            )*
+            MergeCase::Normal
+        }
+    };
+}
+
+macro_rules! merge_copies_dict {
+    (
+        $current_merge: expr,
+        $minor_copies: tt,
+        $major_copies: tt,
+        $get_merge_case: tt $(,)?
+    ) => {
+        {
+            #[allow(unused_mut)]
+            let mut map = TwoWayPathMap::default();
+            let minor = tokenized_path_copies!(map, $minor_copies);
+            let major = tokenized_path_copies!(map, $major_copies);
+            merge_copies_dict(
+                &map, $current_merge, minor, major,
+                merge_case_callback! $get_merge_case,
+            )
+            .into_iter()
+            .map(|(token, source)| {
+                (
+                    map.untokenize(token).to_string(),
+                    (
+                        source.rev,
+                        source.path.map(|t| map.untokenize(t).to_string()),
+                        source.overwritten.into_iter().collect(),
+                    ),
+                )
+            })
+            .collect::<OrdMap<_, _>>()
+        }
+    };
+}
+
+macro_rules! internal_path_copies {
+    (
+        $(
+            $dest: expr => (
+                $src_rev: expr,
+                $src_path: expr,
+                $src_overwrite: tt $(,)?
+            )
+        ),*
+        $(,)*
+    ) => {
+        map!(OrdMap<_, _> {$(
+            String::from($dest) => (
+                $src_rev,
+                $src_path,
+                set!(OrdSet<Revision> $src_overwrite)
+            )
+        ),*})
+    };
+}
+
+macro_rules! combine_changeset_copies {
+    (
+        $children_count: tt,
+        [
+            $(
+                {
+                    rev: $rev: expr,
+                    p1: $p1: expr,
+                    p2: $p2: expr,
+                    actions: [
+                        $(
+                            $Action: ident($( $action_path: expr ),+)
+                        ),*
+                        $(,)?
+                    ],
+                    merge_cases: $merge: tt
+                    $(,)?
+                }
+            ),*
+            $(,)?
+        ],
+        $target_rev: expr $(,)*
+    ) => {{
+        let count = map!(HashMap<Revision, usize> $children_count);
+        let mut combine_changeset_copies = CombineChangesetCopies::new(count);
+        $(
+            let actions = vec![$(
+                $Action($( HgPath::new($action_path) ),*)
+            ),*];
+            combine_changeset_copies.add_revision_inner(
+                $rev, $p1, $p2, actions.into_iter(),
+                merge_case_callback! $merge
+            );
+        )*
+        combine_changeset_copies.finish($target_rev)
+    }};
+}
+
+macro_rules! path_copies {
+    (
+        $( $expected_destination: expr => $expected_source: expr ),* $(,)?
+    ) => {
+        map!(PathCopies {$(
+            HgPath::new($expected_destination).to_owned()
+                => HgPath::new($expected_source).to_owned(),
+        ),*})
+    };
+}

rust/hg-core/src/copy_tracing.rs

@@ -1,3 +1,10 b''
+#[cfg(test)]
+#[macro_use]
+mod tests_support;
+
+#[cfg(test)]
+mod tests;
+
 use crate::utils::hg_path::HgPath;
 use crate::utils::hg_path::HgPathBuf;
 use crate::Revision;