Summary:

Detects compatibility issues in different versions of .NET dependency assemblies, and their relevance to a dependent assembly.

The project was started due to this blog post by Jon Skeet.

Description

Suppose you have a project that depends on assembly Name=myDependency, Version=1.0 but you want to know whether it is runtime compatible with a higher version, 2.0, say.

This project provides a solution which lists all type and member signatures that changed between the versions. Moreover, it can also lists all those differences that are relevant to your assembly. For example if a type is removed but is referenced nowhere in your project, then running against the higher versioned dependency should still be fine.

Note: in this context a 'compatibility issue' means code that, when run, would throw a binding failure exception, e.g. TypeLoadException. This entails that only changes to signatures (as opposed to bodies) of members or types are considered to be compatibility issues: changed behavior of a piece of code whose surface remains unchanged is not considered here.

Example usage

This project can be consumed as CLI or as library. The CLI accepts 2 or 3 paths as arguments:

• 2 args: Paths to an assembly and an assembly of higher version. Potential compatibility issues are listed.
• 3 args: Paths to an assembly, a dependency assembly and a dependency assembly of higher version. Compatibility issues are listed when the main assembly would encounter the higher version at runtime.

Library usages is discussed now.

Project overview

Let's sketch a quick overview of the code hierarchy and responsibilities in this project.

• AssemblyGenerator, which is used for testing purposes only, contains helper methods to generate assemblies on the fly using Roslyn, where they are scanned and run.
• DiffDetector is the project dedicated to solving the first part of the problem, namely to list all differences between two assembly versions. The suggested method for external consumption is CompatiblityIssueCollector.Default.GetCompatibilityIssuesBetween(assembly, otherAssembly). The result is a list of implementations of the interface ICompatibilityIssue.
• UsageDetector is the project dedicated to solving the second part of the problem, namely to filter all differences listed by DiffDetector on relevance to a third assembly, mostly referred to as the 'main assembly'. The suggested method for external consumption is UsageDetector.DetectCompatibilityIssues(collector, mainAssembly, dependencyAssembly, dependencyAssemblyHigherVersion). The result is a list of implementations of the interface IDetectedCompatibilityIssue.
• The CLI project merely wraps this for easy consumption, and can stringify ICompatibilityIssue and IDetectedCompatibilityIssue objects.