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Neo4j Drivers Migration Assistant

The migration assistant for Neo4j language libraries (drivers) scans your codebase and raises issues you should address before upgrading to a more recent version. It doesn't automatically rewrite your code; it only points at where action is needed, providing in-context information on how each hit should be addressed.

The assistant supports codebases in Python, JavaScript, and Go.
For further information see the upgrade guide for each language library: Python, Go, JavaScript, Java, .NET.

Points of care:

  • The assistant can detect most of the changes you need to do in your code, but a small percentage of changelog entries can't be surfaced in this form. For a thorough list of changes across versions, see each driver's migration page.
  • Some of the hits may be false positives, so evaluate each of them.
  • Implicit function calls and other hard to parse expressions will not be surfaced by the default parser. See Accuracy.
  • Your Cypher queries may also need changing, but this tool doesn't analyze them. See Cypher -> Deprecations, additions, and compatibility.

Why doesn't it automatically rewrite code? The main reasons are two:

  1. In many instances, breaking changes are not simple method renames or things that could easily be automatically rewritten. Sometimes the behavior of a function changed, sometimes a method was deprecated without a 1:1 replacement, sometimes a property containing decimal seconds has been split into two properties containing seconds and microseconds separately. In many cases, you need to evaluate how to address the change depending on what behavior your application expects.
  2. We want users to have all the information they need to address changes, and to make it readily available. We also still want the users to be responsible and aware of the changes they make. Automatic rewriting promotes lack of understanding.

Usage

To set up the environment, assuming python3 and pip3 are already installed,

python3 -m venv virtualenvs/neo-migration
source virtualenvs/neo-migration/bin/activate
pip3 install -r requirements.txt

The basic invocation looks like:

python3 main.py -l <codebase-language> <path-to-codebase>

For example, for a python application,

python3 main.py -l python example-projects/python/movies.py

Paths support globbing. You can provide multiple paths as positional arguments. For example (quotes for shell expansion),

python3 main.py -l python 'example-projects/python/*.py' 'example-projects/python/subdir/**/*.py' '/a/full/dir/'

By default the tool runs in interactive mode. To get all the output at once, use --no-interactive. For a list of all options, see -h.

Accuracy

Tree-sitter parser

By default, the assistant works on an AST of your source, relying on tree-sitter to generate it. This makes the deprecation/removal hits fairly accurate (although not perfect: there's no type checking in most cases). However, invocations that materialize only at runtime can't be surfaced.

Here are a few examples containing deprecated usage that would not be raised by the tree-sitter parser:

method_name = 'read_transaction'
locals()['method_name']()
config = {
    'session_connection_timeout': 10,
    'update_routing_table_timeout': 4
}
driver = GraphDatabase.driver(url, auth=auth, **config)
def tx_func(type):
    if type == 'read':
        return 'read_transanction'
    elif type == 'write':
        return 'write_transanction'

getattr(session, tx_func())(callback, args)

Regex parser

The regex parser works with regexes on the raw source code rather that on its AST. To enable it, use --regex-parser.

The regex parser has less awareness of code structure and is thus likely to return more false positives, but is also capable of raising deprecated usage that only gets surfaced at runtime. The best course of action is to run the assistant with the default parser, fix all the surfaced hits, and then run it again with the regex parser.

Example of false positive from the regex parser:

`Node.id` and `Relationship.id` were deprecated and have been superseded by `Node.element_id` and
`Relationship.element_id`. Old identifiers were integers, wereas new elementIds are strings.
This also affects Graph objects as indexing graph.nodes[...] and graph.relationships[...] with integers
has been deprecated in favor of indexing them with strings.

  102
  103 def serialize_movie(movie):
  104     return {
> 105         "id": movie["id"],
  106         "title": movie["title"],
  107         "summary": movie["summary"],
  108         "released": movie["released"],

  Deprecated in: 5.0
  Docs: https://neo4j.com/docs/cypher-manual/current/functions/scalar/#functions-elementid