Task Hierarchy & Prerequisites

Describe the bug

I'm not sure if this is intended behavior, a bug or a potential perf optimization, but I will write this up as a bug for initial discussion. I long thought lage was behaving a certain way but it turns out I was wrong the whole time. The behavior described in this issue seems to be consistent for all versions from 0.29.0 to 2.5.19.

Given a lage config:

module.exports = {
  "pipeline": {
    "build": [
      "^build"
    ],
    "test": [
      "build"
    ],
    "lint": []
  },
  "npmClient": "yarn"
};

that defines build of dependent packages a prerequisite for build of a given package. Additionally, it defines build of its own package as a prerequisite for test task defined in that package.

However, it appears that this actually requires build of the entire repo when running yarn lage test, even for standalone packages and leaf nodes that aren't dependents of any package with test tasks.

The package hierarchy is:

flowchart TD
    base["package-base"]
    leaf["package-leaf"]
    test["package-test"]
    standalone["package-standalone"]

    test --> base
    leaf --> base

ONLY package-test defines a test task. Combined with lage.config.js this should result in the task hierarchy for yarn lage test:

flowchart TD
    basebuild["package-base#build"]
    testbuild["package-test#build"]
    testtest["package-test#test"]

    basebuild --> testbuild
    testbuild --> testtest

To Reproduce

Steps to reproduce the behavior:

1. git clone https://github.com/JasonGore/lage-leaf-nodes
2. yarn
3. yarn lage test

Actual Behavior

Running yarn lage test actually runs build against all packages in the repo, even standalone packages and leaf nodes with no test scripts.

D:\git\repros\lage-leaf-nodes>yarn lage test
yarn run v1.22.17
$ lage test
info Lage task runner - let's make it
info package-base build ▶️ start
info package-leaf build ▶️ start
info package-standalone build ▶️ start
info package-base build ✔️ done  - 0.29s
info package-test build ▶️ start
info package-leaf build ✔️ done  - 0.29s
info package-standalone build ✔️ done  - 0.29s
info package-test build ✔️ done  - 0.28s
info package-test test ▶️ start
info package-test test ✔️ done  - 0.28s
info � Summary
info
info [Tasks Count] success: 5, skipped: 0, incomplete: 0
info ----------------------------------------------
info Took a total of 1.00s to complete
Done in 1.83s.

Expected behavior

A directed command like yarn lage test only runs the prerequisites in the task hierarchy. In other words, build for packages that have test tasks or are dependencies of packages with test tasks. This is also the behavior that occurs when yarn lage test --to package-test is run.

$ lage test
info Lage task runner - let's make it
info package-base build ▶️ start
info package-base build ✔️ done  - 0.29s
info package-test build ▶️ start
info package-test build ✔️ done  - 0.28s
info package-test test ▶️ start
info package-test test ✔️ done  - 0.28s
info � Summary
info
info [Tasks Count] success: 3, skipped: 0, incomplete: 0
info ----------------------------------------------
info Took a total of 1.00s to complete
Done in 1.83s.

Environment/Troubleshooting

If this is an issue with run order of tasks, please paste in the result of lage info test:

info {
info   "command": [
info     "test"
info   ],
info   "scope": [
info     "package-base",
info     "package-leaf",
info     "package-standalone",
info     "package-test"
info   ],
info   "packageTasks": [
info     {
info       "id": "package-test#test",
info       "command": [
info         "yarn",
info         "run",
info         "test"
info       ],
info       "dependencies": [
info         "package-test#build"
info       ],
info       "workingDirectory": "packages/package-test",
info       "package": "package-test",
info       "task": "test"
info     },
info     {
info       "id": "package-base#build",
info       "command": [
info         "yarn",
info         "run",
info         "build"
info       ],
info       "dependencies": [],
info       "workingDirectory": "packages/package-base",
info       "package": "package-base",
info       "task": "build"
info     },
info     {
info       "id": "package-leaf#build",
info       "command": [
info         "yarn",
info         "run",
info         "build"
info       ],
info       "dependencies": [],
info       "workingDirectory": "packages/package-leaf",
info       "package": "package-leaf",
info       "task": "build"
info     },
info     {
info       "id": "package-standalone#build",
info       "command": [
info         "yarn",
info         "run",
info         "build"
info       ],
info       "dependencies": [],
info       "workingDirectory": "packages/package-standalone",
info       "package": "package-standalone",
info       "task": "build"
info     },
info     {
info       "id": "package-test#build",
info       "command": [
info         "yarn",
info         "run",
info         "build"
info       ],
info       "dependencies": [
info         "package-base#build"
info       ],
info       "workingDirectory": "packages/package-test",
info       "package": "package-test",
info       "task": "build"
info     }
info   ]
info }

Start with the reproduction repository and its lage.config.js, then run yarn lage test and compare the task graph with yarn lage test --to package-test and lage info test. Trace how the pipeline prerequisites and package scope are selected; done means yarn lage test runs only package-test#test, its build, and the required package-base#build task.