Tamas Cservenak opened MNG-8283 and commented

Rework CLI, how Maven "boots". Currently MavenCLI is under-maintained, full of tech debt, and blurs boundaries between arg parsing, DI booting and invoking Maven. Hence, is not reusable, like for mvnd where a mutilated copy of this class was needed.
MavenCLIng should alleviate all these problems.

Rationale:

New CLI for Maven. Goals are reusability, extensibility and easier embeddability (a la mvnd). If you build this branch, you will end up with Maven distro that uses "new" maven-cli:org.apache.maven.cling.MavenCling class as entry point instead of "old" maven-embedder:org.apache.maven.cli.MavenCli.

First step is to make "pretty much equivalent" capable CLI as compared to "old", with some exceptions:

• "encryption" ops are gone, those should be in separate tool anyway
• "deprecated and unsupported" CLI options like -llr present ONLY to make Maven fail are gone (now Arg parser will fail).

Current state of affairs is messy, MavenCli mixes everything it can, contains interleaved logic for bootstrapping, arg parsing, default logic and executing Maven. First goal is to clean this up.

Commons CLI are also hidden in this PR, so is ClassWorlds. This basically opens up way to have "alternative" CLI arguments parsers as well.

Currently the "local" (CLI) flow is this:

arg[] -> localParser -> Request -> localInvoker -> maven runs (in situ)

But the point is if you "come up" somehow with a Request instance, one can also do just:

Request -> invoker -> maven runs (somewhere)

Local parser:

• parses CLI args
• infers the defaults
• creates Request object that contains all information needed to run Maven
• can be reused outside of CLI as well
• does NOT fiddle with Plexus, logging, etc.

Local invoker:

• accepts Request object
• deals with configuring env (logging, etc), creating DI container, and running Maven ONLY

There are some experiments ongoing as well, like ForkedInvoker is, we can now make also Tool s.

Issue Links:

• MNG-7354 Refactor MavenCli to ease extensibility
  ("is duplicated by")
• MNG-8267 Drop ConfigurationProcessor support
  ("causes")
• MNG-8282 Disable MNG-0553 IT for Maven 4-beta5+ (feature reworked)
  ("causes")
• MNG-8285 Implement mvnenc, new CLI tool for password management
  ("is required by")

Remote Links:

• GitHub Pull Request #1750
  
• Part One PR #1750
  
• Part Two GH PR #1772
  
• Part Three PR #1775
  
• Part Four PR #1779
  

Backported to: 4.0.0-beta-5