1 files changed, 61 insertions, 0 deletions
diff --git a/cli/lsp/documents.rs b/cli/lsp/documents.rs
index 048e4bedb..5fbfcdf52 100644
--- a/cli/lsp/documents.rs
+++ b/cli/lsp/documents.rs
@@ -12,6 +12,7 @@ use deno_core::error::Context;
 use deno_core::ModuleSpecifier;
 use lspower::lsp::TextDocumentContentChangeEvent;
 use std::collections::HashMap;
+use std::collections::HashSet;
 use std::ops::Range;
 use std::str::FromStr;
 
@@ -138,10 +139,42 @@ impl DocumentData {
 
 #[derive(Debug, Clone, Default)]
 pub struct DocumentCache {
+  dependents_graph: HashMap<ModuleSpecifier, HashSet<ModuleSpecifier>>,
   docs: HashMap<ModuleSpecifier, DocumentData>,
 }
 
 impl DocumentCache {
+  /// Calculate a graph of dependents and set it on the structure.
+  fn calculate_dependents(&mut self) {
+    let mut dependents_graph: HashMap<
+      ModuleSpecifier,
+      HashSet<ModuleSpecifier>,
+    > = HashMap::new();
+    for (specifier, data) in &self.docs {
+      if let Some(dependencies) = &data.dependencies {
+        for dependency in dependencies.values() {
+          if let Some(analysis::ResolvedDependency::Resolved(dep_specifier)) =
+            &dependency.maybe_code
+          {
+            dependents_graph
+              .entry(dep_specifier.clone())
+              .or_default()
+              .insert(specifier.clone());
+          }
+          if let Some(analysis::ResolvedDependency::Resolved(dep_specifier)) =
+            &dependency.maybe_type
+          {
+            dependents_graph
+              .entry(dep_specifier.clone())
+              .or_default()
+              .insert(specifier.clone());
+          }
+        }
+      }
+    }
+    self.dependents_graph = dependents_graph;
+  }
+
   pub fn change(
     &mut self,
     specifier: &ModuleSpecifier,
@@ -166,6 +199,7 @@ impl DocumentCache {
 
   pub fn close(&mut self, specifier: &ModuleSpecifier) {
     self.docs.remove(specifier);
+    self.calculate_dependents();
   }
 
   pub fn contains_key(&self, specifier: &ModuleSpecifier) -> bool {
@@ -183,6 +217,17 @@ impl DocumentCache {
     }
   }
 
+  // For a given specifier, get all open documents which directly or indirectly
+  // depend upon the specifier.
+  pub fn dependents(
+    &self,
+    specifier: &ModuleSpecifier,
+  ) -> Vec<ModuleSpecifier> {
+    let mut dependents = HashSet::new();
+    self.recurse_dependents(specifier, &mut dependents);
+    dependents.into_iter().collect()
+  }
+
   pub fn dependencies(
     &self,
     specifier: &ModuleSpecifier,
@@ -260,6 +305,21 @@ impl DocumentCache {
       .collect()
   }
 
+  fn recurse_dependents(
+    &self,
+    specifier: &ModuleSpecifier,
+    dependents: &mut HashSet<ModuleSpecifier>,
+  ) {
+    if let Some(deps) = self.dependents_graph.get(specifier) {
+      for dep in deps {
+        if !dependents.contains(dep) {
+          dependents.insert(dep.clone());
+          self.recurse_dependents(dep, dependents);
+        }
+      }
+    }
+  }
+
   pub fn set_dependencies(
     &mut self,
     specifier: &ModuleSpecifier,
@@ -267,6 +327,7 @@ impl DocumentCache {
   ) -> Result<(), AnyError> {
     if let Some(doc) = self.docs.get_mut(specifier) {
       doc.dependencies = maybe_dependencies;
+      self.calculate_dependents();
       Ok(())
     } else {
       Err(custom_error(