Port more of member completions + tests

[gabritto]

Follow-up of #811.
In this PR:

• More member completions unit tests.
• Ported code from the vscode TS extension that computed replacement range (i.e. LSP text edit) and filter text.
• Implemented findChildOfKind, which was needed for the tuple completion case.

The code in ls/testsetup.go is temporary while we don't have real fourslash test infra, and is used for parsing markers in the unit tests. I got it from @navya9singh's signature help branch. I also tested the scenarios in the unit tests in vscode.

[Copilot]

Pull Request Overview

This PR adds more unit tests for member completions while improving several completion‐related helper functions and message clarity. Key changes include:

• Refining the implementation of findChildOfKind in utilities.go (with updated parameter naming and token‐scanning logic) and marking functions for signature help.
• Adding a temporary test setup file for marker parsing in testsetup.go and updating the error message in languageservice.go.
• Renaming internal functions in astnav/tokens.go and introducing ForEachChildAndJSDoc in ast/utilities.go to support more comprehensive AST traversal.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/ls/utilities.go	Updated findChildOfKind with improved naming and token scanning logic.
internal/ls/testsetup.go	Introduced temporary test setup for marker parsing in unit tests.
internal/ls/languageservice.go	Enhanced error message to include the file name.
internal/ls/completions.go	Renamed deprecation function and adjusted text-edit/commit characters logic.
internal/astnav/tokens.go	Renamed visitEachChildAndJSDoc to exported VisitEachChildAndJSDoc.
internal/ast/utilities.go	Added ForEachChildAndJSDoc to handle complete child traversal including JSDoc.

Comments suppressed due to low confidence (6)

internal/ls/utilities.go:85

• Renaming the parameter from 'node' to 'containingNode' improves clarity; ensure that all references within the function remain consistent.

func findChildOfKind(containingNode *ast.Node, kind ast.Kind, sourceFile *ast.SourceFile) *ast.Node {

internal/ls/completions.go:1250

• The duplicate declaration of 'textEdit' has been removed and the text edit adjustment logic for member completions is restructured; verify that this change is fully covered by unit tests.

return &lsproto.CompletionItem{

internal/astnav/tokens.go:137

• Renaming 'visitEachChildAndJSDoc' to 'VisitEachChildAndJSDoc' for export consistency is appropriate; ensure that its usage is reflected in all affected call sites.

VisitEachChildAndJSDoc(current, sourceFile, nodeVisitor)

internal/ls/testsetup.go:64

• [nitpick] Ensure that the new test setup implementation covers all marker parsing scenarios, including edge cases with multiple files or unusual marker formats.

testFileInfo := parseFileContent(currentFileContent, fileName, &markerPositions, &markers)

internal/ast/utilities.go:2796

• The new ForEachChildAndJSDoc function provides a tidy way to traverse child nodes along with JSDoc comments; verify that its behavior is as expected for all AST node variants.

func ForEachChildAndJSDoc(node *Node, sourceFile *SourceFile, v Visitor) bool {

internal/ls/languageservice.go:69

• The updated error message now includes the file name, which improves debuggability; verify that this aligns with the project's logging standards.

panic("file not found: " + fileName)