rchildress87
81589c1244
### Why the changes in this PR are needed? `text/template`'s field evaluator (`text/template.(*state).evalField`, `exec.go`) calls`reflect.Value.MethodByName` with a non-constant name. The Go linker treats a reachable non-constant`MethodByName` as a signal to disable **method-level dead-code elimination for the whole binary** (see `cmd/link/internal/ld/deadcode.go` and golang/go#72895). Two OPA code paths pull stdlib `text/template` into the reachable graph of ordinary embedders: 1. **Compiler frontend** — `ast.Compiler.Compile → … → gojsonschema.formatErrorDescription → text/template`. Reached unconditionally by anything that compiles Rego. 2. **`strings.render_template` builtin** (`v1/topdown/template.go`) — registered in the topdown builtin table, reachable in anything that links Rego evaluation. So an embedder of OPA's compiler/eval retains its entire reachable method surface — a large binary-size regression, hundreds of MB in the reporter's case (#7903). Both edges must go before the linker re-enables method-level DCE for that embedder. ### What are the changes in this PR? Vendor a self-contained, method-less copy of `text/template` under `internal/methodlesstemplate` and point both call sites at it. **No external dependency** (`go.mod`/`go.sum` unchanged). - Copied verbatim from **Go 1.25.8**: `doc.go`, `exec.go`, `funcs.go`, `option.go`, `template.go`, plus `internal/fmtsort/sort.go`. Go's BSD `LICENSE` is preserved in the vendored directory and every file keeps its `The Go Authors` copyright header. - Stdlib `text/template/parse` is reused unchanged (the parser has no `MethodByName`/`evalField` edge, so it does not defeat DCE). - `helper.go` (`ParseFiles`/`ParseGlob`/`ParseFS`) is dropped — the OPA call sites only need `New`/`Parse`/`Execute`, and nothing in the kept files references it. - **The only edit to the copied code** is removing the `MethodByName` branch in `exec.go`'s `evalField` (method resolution on the data value). Everything else is byte-identical, so re-syncing to a newer Go release is a diff-and-reapply of that single branch removal. - `internal/gojsonschema` (commit 1) and `v1/topdown` (commit 2) import the vendored package. The gojsonschema engine is retained in full, so `ErrorTemplateFuncs` (its `FuncMap` extension point) keeps working — **no public symbol is removed**. Rego values and gojsonschema `ErrorDetails` decode to `map[string]any`/`[]any`/scalars, which have no methods, so removing method resolution is a provable no-op for these callers. ### Notes to assist PR review: - **Diff review tip**: `doc.go`/`funcs.go`/`option.go`/`template.go`/`internal/fmtsort/sort.go` are **byte-identical** to the Go 1.25.8 originals. Only `exec.go` differs, in exactly two hunks: the `internal/fmtsort` → vendored import path, and the removed `MethodByName` block (replaced by a comment explaining the DCE rationale). - **Fidelity — render_template**: the `rendertemplate` conformance cases (incl. `complex` range/if/vars, `simpleint` `%v`, `missingkey` → `<undefined>`) pass **unchanged**. - **Fidelity — gojsonschema**: same engine (method-less), validation-error output unchanged; existing `internal/gojsonschema` and `v1/ast` tests pass. - **Tests**: `TestNoStdlibTextTemplateImport` in both `internal/gojsonschema` and `v1/topdown` scans every non-test file and asserts none import stdlib `text/template`/`html/template`. `go build ./...`, `go vet ./...` OK; `go mod tidy` is a no-op. - **Lint**: the vendored directory is added to the golangci-lint path exclusions, mirroring the existing `internal/gojsonschema` precedent — the copy is verbatim stdlib, and linting it against OPA's house rules would force divergence from upstream Go (it trips ~31 stdlib-idiom issues) and break the diff-and-reapply re-sync. - **Attribution**: the vendored code is Go stdlib only (BSD, `The Go Authors`); it contains no third-party/DataDog code. ### Further comments: - **Scope**: this restores method-level DCE for embedders of OPA's **compiler/eval**. The standalone `opa` binary additionally links `v1/server`, which imports `html/template` (a wrapper over `text/template`) — a separate, independent edge left as a follow-up. Embedders that don't link the server (the common case) get the full win from this PR. - Root cause: golang/go#72895. Closes #7903 for compiler/eval embedders. --------- Signed-off-by: Dick Childress <dick.childress@icearp.net> Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
1.5 KiB
methodlesstemplate
A vendored copy of the Go standard library's text/template, with one behavioral change: the
method-calls-on-data branch in exec.go's evalField (reflect.Value.MethodByName) is removed.
A reachable, non-constant reflect.Value.MethodByName makes the Go linker disable method-level
dead-code elimination for the entire binary (golang/go#72895). OPA reaches text/template from
its compiler (schema errors) and the strings.render_template builtin, so that one edge retains the
full reflected method surface of every embedder — a large binary-size regression (#7903). Rego
values and gojsonschema ErrorDetails decode to map[string]any / []any / scalars, which have no
methods, so eliding the data-method lookup is a behavioral no-op while restoring DCE.
Only exec.go differs from the upstream stdlib. doc.go, funcs.go, option.go, template.go,
and internal/fmtsort/sort.go are byte-identical to their Go release; text/template/parse is
reused via its normal import. helper.go (ParseFiles/ParseGlob/ParseFS) is intentionally not
vendored. Go's BSD LICENSE and per-file copyright headers are preserved.
Regenerating
Do not hand-edit these files. To re-sync to a new Go release, run under the target toolchain:
GOTOOLCHAIN=go1.26.0 build/regen-methodless-template.sh
The script copies the stdlib files verbatim and re-applies the single method-elision edit. If the edit no longer applies (the stdlib changed that region), the script fails and the elision must be re-derived and the patch in the script updated.