Resolve modules through dagger-module.toml

[eunomie]

The dang-sdk half of dagger/go-sdk#10 — the same bug, in the same shape.

The bug

mod() resolved a workspace path to its owning module with a single find-up for dagger.json. Modules carrying a dagger-module.toml instead have no dagger.json to find, so every lookup against them failed with no Dagger module found containing path. Once dagger/dagger#13651 lands, that is every workspace-managed module.

Verified: against a migrated module, mod reports no Dagger module found containing path: toml-app before this change and resolves after it.

The fix

Find up both dagger-module.toml and dagger.json and keep the closest match, checking [runtime] source = "dang" for the former and leaving the existing dagger.json check untouched.

Comparing both in one pass — rather than trying dagger-module.toml first and falling back — is what keeps find-up's closest-wins semantics: an ancestor's dagger-module.toml must not shadow a legacy module that sits deeper, which is the shape a partially migrated workspace has.

A lookup against another SDK's module now names the runtime that owns it — does not use the Dang SDK: <path> (runtime source: go) — instead of reporting no module at all.

findUp: false is untouched and still bypasses resolution.

Scope: no as-sdk tier here

dagger/go-sdk#10 has a third, higher-precedence tier reading the workspace's [[modules.<sdk>.as-sdk.modules]] entries. It is deliberately absent here: this module declares engineVersion = "v0.20.8", and currentModule.asSDK does not exist at that version — referencing it is a compile error, not a catchable one. This repo also has no dagger.toml and no as-sdk config, and generateAll still discovers modules by scanning the filesystem.

Adding that tier means migrating this SDK to the 1.0 schema first (engine version bump, .{x} → .{{x}}), which is its own change. The two-tier resolver here fixes the reported bug on the current schema.

Verification

There is no e2e module in this repo, so this was checked against a synthetic workspace: a migrated dagger-module.toml module resolves; legacy find-up from a nested path resolves; a go-owned module is rejected naming go; a partially migrated workspace resolves to the deeper legacy module rather than the migrated ancestor; a legacy non-dang module is rejected; and findUp: false with /x/ still returns x/. Worth noting that none of that is committed — this repo has no test harness to put it in.

[TomChv]

Fixed by #8 already