Track the reason why an immediate change was detected

Summary: Add an `ImpactReason` enum indicating the path we took in `immediate_target_changes` to mark a target as affected, then propagate that reason through rdeps in `recursive_target_changes`. Carry the reason all the way through to BTD's output so that we can inspect it in Skycastle. Also summarize the number of affected targets with each reason in the BTD_SUCCESS event.

Reviewed By: ndmitchell

Differential Revision: D54436861

fbshipit-source-id: 800607b2796cd94f4f6965c0555e143cb468c9a2

btd/Cargo.toml

@@ -15,6 +15,7 @@ derive_more = "0.99.3"
 fbinit = { workspace = true }
 glob = "0.3.0"
 itertools = "0.10.5"
+parse-display = "0.8.2"
 serde = {version = "1.0", features = ["derive"]}
 serde_json = "1.0.66"
 tempfile = "3.1.0"

btd/src/check.rs

@@ -23,6 +23,7 @@ use crate::buck::types::Package;
 use crate::buck::types::TargetLabel;
 use crate::buck::types::TargetPattern;
 use crate::changes::Changes;
+use crate::diff::ImpactReason;
 
 #[derive(Debug, Error, Serialize)]
 pub enum ValidationError {
@@ -141,15 +142,15 @@ pub fn check_errors(base: &Targets, diff: &Targets, changes: &Changes) -> Vec<Va
 pub fn check_dangling(
     base: &Targets,
     diff: &Targets,
-    immediate_changes: &[&BuckTarget],
+    immediate_changes: &[(&BuckTarget, ImpactReason)],
     universe: &[TargetPattern],
 ) -> Vec<ValidationError> {
     let exists_after = diff.targets_by_label_key();
     let base_targets_map = base.targets_by_label_key();
 
     let mut errors = Vec::new();
     // Lets check if dangling edges were introduced.
-    for target in immediate_changes.iter() {
+    for (target, _) in immediate_changes.iter() {
         for dep in target.deps.iter() {
             let key = dep.key();
             // Only check newly introduced dangling dependencies that are
@@ -357,7 +358,7 @@ mod tests {
                     target_entry("aaa", &[]),
                     target_entry("bbb", &["aaa", "ccc"])
                 ]),
-                &[&modified_target],
+                &[(&modified_target, ImpactReason::Inputs)],
                 &[TargetPattern::new("foo//...")],
             )
             .len(),
@@ -376,7 +377,7 @@ mod tests {
                     target_entry("bbb", &["aaa"]),
                     target_entry("ccc", &["ddd"])
                 ]),
-                &[&modified_target],
+                &[(&modified_target, ImpactReason::Inputs)],
                 &[TargetPattern::new("foo//...")],
             )
             .len(),
@@ -395,7 +396,7 @@ mod tests {
                     target_entry("aaa", &["ccc"]),
                     target_entry("bbb", &["aaa"])
                 ]),
-                &[&modified_target],
+                &[(&modified_target, ImpactReason::Inputs)],
                 &[TargetPattern::new("foo//...")],
             )
             .len(),
@@ -413,7 +414,7 @@ mod tests {
                     target_entry("aaa", &["ccc"]),
                     target_entry("bbb", &["aaa"])
                 ]),
-                &[&modified_target],
+                &[(&modified_target, ImpactReason::Inputs)],
                 &[TargetPattern::new("foo//...")],
             )
             .len(),
@@ -431,7 +432,7 @@ mod tests {
                     target_entry("aaa", &[]),
                     target_entry("bbb", &["aaa"])
                 ]),
-                &[&modified_target],
+                &[(&modified_target, ImpactReason::Inputs)],
                 &[TargetPattern::new("foo//...")],
             )
             .len(),