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Phase 0: Skeleton

Goal​

Establish the package3/erlang/ directory structure, define the SkipReason and BridgeError types, implement the Go-side ETF encoder/decoder, and write the rebar3 workspace synthesiser skeleton. No actual package fetching or type translation yet.

Gate​

go test ./package3/erlang/... passes with:

  • ETF round-trip tests: encode then decode for all in-table types (integer, float, boolean, atom/string, binary/bytes, list, 2-tuple, 3-tuple, 4-tuple, pid, reference, nil/undefined).
  • SkipReason string representation covers all 17 skip codes.
  • Build.SynthRebar3Config produces a syntactically valid Erlang term file for a 3-package dep set.

Files to touch​

FileDescription
package3/erlang/README.mdPointer to MEP-66 spec.
package3/erlang/errors/errors.goSkipReason constants + SkipReport struct + BridgeError type.
package3/erlang/errors/errors_test.goString representation round-trip.
package3/erlang/etf/etf.goETF tag constants + Decode([]byte) (interface{}, error) + Encode(interface{}) ([]byte, error).
package3/erlang/etf/etf_test.goRound-trip tests for all supported tag types.
package3/erlang/build/driver.goDriver struct: SynthRebar3Config, SynthRebar3Lock, RunRebar3Compile.
package3/erlang/build/driver_test.goSynthRebar3Config golden-file test.

SkipReason codes (phase 0)​

const (
    SkipAnyTerm          SkipReason = iota // any() / term()
    SkipBitstring                          // bitstring()
    SkipCharlist                           // string() (erlang charlist)
    SkipComplexUnion                       // 3+ branch union, no ok/error
    SkipEDoc                               // fell back to EDoc (no BEAM abstract code)
    SkipFunArgNotInTable                   // fun arg type not in table
    SkipIodata                             // iodata() / iolist()
    SkipNonOkErrorUnion                    // 2-branch union, not ok/error pattern
    SkipNoSpec                             // exported function has no -spec
    SkipNoTypeinfo                         // no abstract code AND no EDoc
    SkipRecursiveType                      // user type alias is recursive
    SkipRemoteType                         // remote_type not in deps
    SkipTypedMap                           // #{K := V} map type
    SkipUntypedFun                         // fun() untyped
    SkipUntypedMap                         // map() untyped
    SkipUntypedTuple                       // tuple() untyped
    SkipElixirRuntime                      // requires Elixir runtime
)

ETF types supported in phase 0​

// etf.go (phase 0 subset)
type Atom string          // ETF ATOM_UTF8_EXT / SMALL_ATOM_UTF8_EXT
type Tuple []interface{}  // ETF SMALL_TUPLE_EXT / LARGE_TUPLE_EXT
type List []interface{}   // ETF LIST_EXT / NIL_EXT
type Pid struct {         // ETF PID_EXT / NEW_PID_EXT
    Node     Atom
    ID       uint32
    Serial   uint32
    Creation uint32
}
type Reference struct {   // ETF REFERENCE_EXT / NEW_REFERENCE_EXT
    Node     Atom
    Creation uint32
    IDs      []uint32
}

rebar.config synthesis (phase 0)​

// build/driver.go
type DepEntry struct {
    Name    string
    Version string // exact, from mochi.lock
}

func (d *Driver) SynthRebar3Config(deps []DepEntry, otpVsn string) string

Output example:

{erl_opts, [debug_info]}.

{deps, [
  {cowboy, "2.12.0"},
  {hackney, "1.20.0"},
  {jose, "1.11.0"}
]}.

{minimum_otp_vsn, "25"}.

Sub-phase decomposition​

Phase 0 is a single unit; no sub-phases are expected.

Cross-references​

  • Phase 1 builds the Hex.pm client on top of this skeleton.
  • MEP-66 §1 for the pipeline context.