compiler: Support Querying For Files In Preprocessed Code

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/Common/SourceCode.swift

@@ -129,6 +129,22 @@ public struct FileSourceLocation: Equatable, CustomStringConvertible {
         return "\(location)"
       }).joined(separator: ",") + ")"
   }
+
+  public func pathForLocation(_ location: Int) -> FilePath? {
+
+    let queried_location = SourceLocation(location, 1)
+    if !self.location.contains(queried_location) {
+      return .none
+    }
+
+    for nested in self.nested {
+      if nested.location.contains(queried_location) {
+        return nested.pathForLocation(location)
+      }
+    }
+
+    return self.getPath()
+  }
 }
 
 /// Represent preprocessed P4 code.
@@ -197,6 +213,10 @@ public struct SourceCode {
   public func getLocations() -> FileSourceLocation {
     return self.locations
   }
+
+  public func pathForLocation(_ location: Int) -> FilePath? {
+    return self.locations.pathForLocation(location)
+  }
 }
 
 func do_preprocess(

TestData/Sources/file-loc-parser-state.p4

@@ -0,0 +1,9 @@
+    state start {
+        Testing ts;
+        ts.yesno = true;
+        ts.count = 5;
+        transition select (ts.count == 5) {
+            true: accept;
+            false: reject;
+        };
+    }

TestData/Sources/file-loc-parser.p4

@@ -0,0 +1,3 @@
+parser main_parser() {
+#include <file-loc-parser-state.p4>
+}

TestData/Sources/file-loc.p4

@@ -0,0 +1,5 @@
+struct Testing {
+    bool yesno;
+    int count;
+};
+#include <file-loc-parser.p4>

Tests/p4rseTests/SupportTests/SourceCode.swift

@@ -185,6 +185,27 @@ import TreeSitterP4
   #expect(source.getSource(annotated: true) == expected)
 }
 
+@Test func test_preprocessor_nested_includes_get_file_location() async throws {
+  let sm = SourceManager(["./TestData/Sources/"], FileManager())  // Add a FileManager to get absolute paths.
+  let prep = SourceCodePreprocessor(sm)
+  let file = FilePath.init(stringLiteral: "./TestData/Sources/file-loc.p4")
+
+  let source = try! (#UseOkResult(prep.preprocess(file)))
+
+  let expected_file = FilePath.init(FileManager().currentDirectoryPath + "/" + file.string)
+    .lexicallyNormalized()
+  let expected_nested_file = sm.firstExisting("file-loc-parser.p4")!.lexicallyNormalized()
+  let expected_nested_nested_file = sm.firstExisting("file-loc-parser-state.p4")!
+    .lexicallyNormalized()
+
+  let found_file = try! #require(source.pathForLocation(0))
+  let found_nested_file = try! #require(source.pathForLocation(55))
+  let found_nested_nested_file = try! #require(source.pathForLocation(78))
+
+  #expect(found_file == expected_file)
+  #expect(found_nested_file == expected_nested_file)
+  #expect(found_nested_nested_file == expected_nested_nested_file)
+}
 
 @Test func test_source_location_contains() async throws {
   let outer = SourceLocation(0..<500)