lsp/eval: rework transitioning through imports

There was duplication in the existing code: import specs would be
processed both during their own evaluation, and when path evaluation led
to an imported package.

This CL avoids that duplication, leading to simplification of path
traversal code (`expandNavigables`), and greater consistency.

Signed-off-by: Matthew Sackman <[e-mail]>
Change-Id: I806f834a51031ddc746d01cb90d726a188bcbc57
Reviewed-on: https://cue.gerrithub.io/c/cue-lang/cue/+/1229417
Unity-Result: CUE porcuepine <[e-mail]>
Reviewed-by: Daniel Martí <[e-mail]>
TryBot-Result: CUEcueckoo <[e-mail]>

internal/lsp/eval/eval.go

···
 			// For all the packages that import us, find where usages of
 			// this package appears.
 			ip := nav.evaluator.ip
-			for _, remotePkgDfns := range nav.evaluator.pkgImporters() {
-				navsWorklist = append(navsWorklist, remotePkgDfns.initialNavsForImport(ip)...)
+			for _, remotePkg := range nav.evaluator.pkgImporters() {
+				navsWorklist = append(navsWorklist, remotePkg.initialNavsForImport(ip)...)
 			}
 		}
 	}
···
 
 		nav.eval()
 
-		for _, fr := range nav.frames {
-			spec, ok := fr.node.(*ast.ImportSpec)
-			if !ok {
-				continue
-			}
-			pkgEval := fr.fileEvaluator.evaluator
-			ip := pkgEval.parseImportSpec(spec)
-			if ip == nil {
-				continue
-			}
-			pkgEval = pkgEval.forPackage(*ip)
-			if pkgEval == nil {
-				continue
-			}
-			pkgFrame := pkgEval.pkgFrame
-			pkgFrame.eval()
-			for _, fileFr := range pkgFrame.childFrames {
-				worklist = append(worklist, fileFr.navigable)
-			}
-		}
-
 		worklist = slices.AppendSeq(worklist, maps.Keys(nav.resolvesTo))
 	}
 	return navsSet
···
 					remotePkgEvaluator = New(ast.ImportPath{}, nil, nil, nil)
 				}
 
-				// We add a path that records that the name of this import
-				// spec resolves to the remote package.
+				// DefinitionsForOffset always traverses a path, so here
+				// we add a path so that DefinitionsForOffset on this
+				// import spec reports the package declarations of the
+				// remote pkg.
 				p := &path{
 					frame: f,
 					components: []pathComponent{{
···
 					}},
 				}
 				f.childPaths = append(f.childPaths, p)
+
+				// Any path that actually traverses into the remote pkg
+				// can do so by following the resolvesTo of this frame's
+				// navigable. Rather than resolving to the remove pkg
+				// declarations, we must resolve to the files that make up
+				// the remote pkg.
+				remotePkgFileFrames := remotePkgEvaluator.pkgFrame.childFrames
+				remotePkgNavs := make([]*navigable, len(remotePkgFileFrames))
+				for i, remoteFileFr := range remotePkgFileFrames {
+					remotePkgNavs[i] = remoteFileFr.navigable
+				}
+				f.navigable.ensureResolvesTo(remotePkgNavs)
 
 				// We also record that we are using those package
 				// decls. This means that from the result of resolving the