mesh-delivery/modules/mesh-delivery-checker/internal/check/beside.go

package check

import (
	"context"
	"strconv"
)

// BesideRef is a sibling repository a repository's tests read, placed beside the fetched tree as a plain directory (ADR
// 0484 clause 4). Ref names the pull request's head when the commit is only there.
type BesideRef struct {
	Repository string `json:"repository"`
	Commit     string `json:"commit"`
	Ref        string `json:"ref,omitempty"`
	// atTrunk says the sibling was read at its trunk's head, so a move of that trunk puts the verdict out of date and is
	// carried (novox/hq ADR 0548 §6). Never sent: the node-engine at the commit the mesh runs, mesh-sdk at a pin and a
	// group's member at its head do not move with a trunk.
	atTrunk bool
	// runs says the sibling was read at the commit the mesh runs (the node-engine, the indexer's record of mesh-host): a new
	// running commit puts the verdict out of date and is carried (ADR 0548 §6). Never sent.
	runs bool
}

// NodeEngineModule is the module whose running commit the node-engine sibling is read at.
const NodeEngineModule = nodeEngineModule

const (
	catalogueRepository = "novox/mesh-catalog"
	nodeEngineRepo      = "novox/mesh-host"
	nodeEngineModule    = "mesh-host"
	controllerRepo      = "novox/mesh-controller"
)

// besideRules are the repositories each core repository's tests read, as the tests state it (mesh-sdk go/internal/beside
// beside.go): the catalogue, the node-engine, the SDK, and the delivery's pinned forge dependencies (mesh-catalog
// checks/deps). Which commit of each is besideCommit's rule. No repository's tests read the controller, which ended by its
// unassignment (novox/hq ADR 0590, issue 1126); its own repository keeps its siblings while it holds a module.
var besideRules = map[string][]string{
	controllerRepo:        {catalogueRepository, nodeEngineRepo, SDKRepository},
	nodeEngineRepo:        {catalogueRepository, SDKRepository},
	SDKRepository:         {catalogueRepository, nodeEngineRepo},
	catalogueRepository:   {SDKRepository},
	"novox/mesh-delivery": {SDKRepository, catalogueRepository},
}

// besideFor are the siblings a pull request's tests read (ADR 0484 clause 4): the catalogue at its trunk, always, even in a
// group holding a catalogue pull request; the node-engine at the commit the mesh runs (the commit of the indexer's module
// mesh-host, its trunk head when none is known); mesh-sdk, for the controller's tests, at the commit the controller's go.mod
// pins; any other sibling at the head of the group's pull request for it when the group holds one, else at its trunk. And
// first, the change's own repository at the trunk it is merged onto, so a test comparing a shrink-only list with the
// trunk's copy reads it at $MESH_CHECK_BESIDE/<name> (issue 1887 A12, ADR 0529 §2).
func (j *Examiner) besideFor(ctx context.Context, c *Case, p Pull) ([]BesideRef, error) {
	var heads map[string]string
	if j.Trunks != nil {
		heads = j.Trunks.Heads()
	}
	var out []BesideRef
	if p.Trunk != "" {
		out = append(out, BesideRef{Repository: p.Repository, Commit: p.Trunk})
	}
	for _, repo := range besideRules[p.Repository] {
		switch {
		case repo == catalogueRepository:
			if head := heads[repo]; head != "" {
				out = append(out, BesideRef{Repository: repo, Commit: head, atTrunk: c.member(repo) == nil})
			}
		case repo == nodeEngineRepo:
			commit := ""
			if j.Runs != nil {
				commit = j.Runs.CommitOf(nodeEngineModule)
			}
			atTrunk := false
			if commit == "" {
				commit, atTrunk = heads[repo], true
			}
			if commit != "" {
				// Named in the verdict either way (ADR 0548 §6, issue 568's own example): at the commit the mesh runs, a new
				// running commit puts the verdict out of date; at the trunk, a trunk move does (Checker.besideNow).
				out = append(out, BesideRef{Repository: repo, Commit: commit, atTrunk: atTrunk, runs: !atTrunk})
			}
		default:
			if member := c.member(repo); member != nil {
				out = append(out, BesideRef{Repository: repo, Commit: member.Head, Ref: refOf(member.Number)})
			} else if head := heads[repo]; head != "" {
				out = append(out, BesideRef{Repository: repo, Commit: head, atTrunk: true})
			}
		}
	}
	return out, nil
}

func (c *Case) member(repository string) *Pull {
	for i := range c.Pulls {
		if c.Pulls[i].Repository == repository {
			return &c.Pulls[i]
		}
	}
	return nil
}

func refOf(number int) string {
	if number <= 0 {
		return ""
	}
	return "refs/pull/" + strconv.Itoa(number) + "/head"
}

// besideAtTrunk are the siblings of refs read at their trunk's head that the case does not merge, by repository: what a
// verdict names as Beside (ADR 0548 §6).
func besideAtTrunk(c *Case, refs []BesideRef, into map[string]string) {
	for _, r := range refs {
		if _, merged := c.Trunk[r.Repository]; (r.atTrunk || r.runs) && !merged {
			into[r.Repository] = r.Commit
		}
	}
}