[BUG] ppx_expect output is being included in built javascript files

[WardBrian]

Describe the bug

I have tests in my code using ppx_expect. The string of these tests can be found in the generated .bc.js file from JSOO

Expected behavior That this code would not survive JS code generation.

Versions 5.5.2

[TyOverby]

Js_of_ocaml does a fine job of dead-code elimination, but because expect-tests are enabled or disabled vis environment variable, you need to tell jsoo that the expect-test env var is always empty. I forget which var it is, and I also forget how to configure dune to do this, but it does work!

[hhugo]

In general, you want this code to survive JS code generation so that you can run test in JavaScript.

You should be able to drop the tests with the following js_of_ocaml compile flags. --setenv FORCE_DROP_INLINE_TEST=true.

This allows js_of_ocaml to perform static evaluation of the following code https://github.com/janestreet/ppx_inline_test/blob/f88526ee10c8d815653fff621a2816834c81c12d/runtime-lib/ppx_inline_test_lib.ml#L118

  let force_drop =
    try
      ignore (Sys.getenv "FORCE_DROP_INLINE_TEST" : string);
      true
    with
    | Not_found -> false
  ;;

  let get () =
    (* This is useful when compiling to javascript.
       Js_of_ocaml can statically evaluate [Sys.getenv "FORCE_DROP_INLINE_TEST"]
       and inline the result ([`Ignore]) whenever [get ()] is called.
       Unit tests can then be treated as deadcode since the argument [f] of the [test]
       function below is never used. *)
    if force_drop then `Ignore else !action
  ;;

[WardBrian]

Thanks. Unfortunately I am still seeing the test strings in the file even after adding

(js_of_ocaml
  (flags (:standard --setenv FORCE_DROP_INLINE_TEST=true)))

to my dune config

[hhugo]

You also need to build with --profile release dune flag. Otherwise, separate compilation is used for JavaScript compilation and no cross module dead code happen

[hhugo]

Or you can set (js_of_ocaml (compilation_mode whole_program)) in dune env. See https://dune.readthedocs.io/en/stable/reference/dune/env.html#env

[WardBrian]

I was using --profile release as well

[hhugo]

I can't reproduce. I see the expect_test being dropped when use what has been mentioned in the issue. Can you share some code ? if you're using dune, you should probably try to pass --verbose to check that the expected flags are there.

[WardBrian]

Let me update to 5.7.0 and then see if I can give you a reproducer

[WardBrian]

The code base I am working with is https://github.com/stan-dev/stanc3.

I put together a gist with my dune config, the output of dune verbose, and the generated .js file. The command I used in full was dune build src/stancjs/ --profile=release --force --display=verbose > dune_output.txt 2>&1

Here is a string which only appears in the source code as part of the expect tests:

(RequireAllCondition (Exact stan::is_vt_not_complex) (TemplateType T0__1__))

$ grep "(RequireAllCondition (Exact stan::is_vt_not_complex) (TemplateType T0__1__))" ./stancjs.bc.js -c
1

[hhugo]

It could be a regression in ppx_inline_test or ppx_expect v0.17.0

[hhugo]

Could you try to downgrade to v0.16.0 (assuming you are indeed using v0.17.0)

[WardBrian]

I am using 0.16.0. Here's my opam list

Details

``` # Packages matching: installed # Name # Installed # Synopsis angstrom 0.16.0 Parser combinators built for speed and memory-efficiency astring 0.8.5 Alternative String module for OCaml base v0.16.3 Full standard library replacement for OCaml base-bigarray base base-bytes base Bytes library distributed with the OCaml compiler base-threads base base-unix base base-windows v0.16.3 Full standard library replacement for OCaml base_bigstring v0.16.0 String type based on [Bigarray], for use in I/O and C-bindings base_bigstring-windows v0.16.0 String type based on [Bigarray], for use in I/O and C-bindings base_quickcheck v0.16.0 Randomized testing framework, designed for compatibility with Base base_quickcheck-windows v0.16.0 Randomized testing framework, designed for compatibility with Base bigstringaf 0.9.1 Bigstring intrinsics and fast blits based on memcpy/memmove bin_prot v0.16.0 A binary protocol generator bin_prot-windows v0.16.0 A binary protocol generator bisect_ppx 2.8.3 Code coverage for OCaml camlp-streams 5.0.1 The Stream and Genlex libraries for use with Camlp4 and Camlp5 chrome-trace 3.10.0 Chrome trace event generation library cmdliner 1.2.0 Declarative definition of command line interfaces for OCaml conf-bash 1 Virtual package to install the Bash shell conf-flambda-windows 1 conf-gcc-windows 1 conf-gcc-windows64 1 Virtual package specifying the location of GCC cross-compiler for 64-bit Windows conf-libpcre 1 Virtual package relying on a libpcre system installation conf-pkg-config 3 Check if pkg-config is installed and create an opam switch local pkgconfig folder core v0.16.1 pinned to version v0.16.1 core-windows v0.16.1 Industrial strength alternative to OCaml's standard library core_kernel v0.16.0 Industrial strength alternative to OCaml's standard library core_unix v0.16.0 Unix-specific portions of Core cppo 1.6.9 Code preprocessor like cpp for OCaml csexp 1.5.2 Parsing and printing of S-expressions in Canonical form dot-merlin-reader 4.9 Reads config files for merlin dune 3.10.0 Fast, portable, and opinionated build system dune-build-info 3.10.0 Embed build information inside executable dune-configurator 3.10.0 Helper library for gathering system configuration dune-configurator-windows 2.5.1 Helper library for gathering system configuration dune-private-libs 2.5.1 Private libraries of Dune dune-private-libs-windows 2.5.1 Private libraries of Dune dune-rpc 3.10.0 Communicate with dune using rpc dyn 3.10.0 Dynamic type either 1.0.0 Compatibility Either module expect_test_helpers_core v0.16.0 Helpers for writing expectation tests fiber 3.7.0 Dune's monadic structured concurrency library fieldslib v0.16.0 Syntax extension to define first class values representing record fields, to get and set record fields, iterate and fold over all fields of a record and create new record values fieldslib-windows v0.16.0 Syntax extension to define first class values representing record fields, to get and set record fields, iterate and fold over all fields of a record and create new record values fix 20230505 Algorithmic building blocks for memoization, recursion, and more flexdll-windows 0.42 FlexDLL is a Windows dynamic linker extension allowing DLLs to depend on each other fmt 0.9.0 OCaml Format pretty-printer combinators fmt-windows 0.9.0 OCaml Format pretty-printer combinators fpath 0.7.3 File system paths for OCaml gen 1.1 Iterators for OCaml, both restartable and consumable int_repr v0.16.0 Integers of various widths int_repr-windows v0.16.0 Integers of various widths jane-street-headers v0.16.0 Jane Street C header files jane-street-headers-windows v0.16.0 Jane Street C header files jbuilder 1.0+beta20.2 Fast, portable and opinionated build system js_of_ocaml 5.7.0 Compiler from OCaml bytecode to JavaScript js_of_ocaml-compiler 5.7.0 Compiler from OCaml bytecode to JavaScript jst-config v0.16.0 Compile-time configuration for Jane Street libraries jst-config-windows v0.16.0 Compile-time configuration for Jane Street libraries lambda-term 3.3.2 Terminal manipulation library for OCaml landmarks 1.4 A simple profiling library landmarks-ppx 1.4 Preprocessor instrumenting code using the landmarks library logs 0.7.0 Logging infrastructure for OCaml lwt 5.7.0 Promises and event-driven I/O lwt_react 1.2.0 Helpers for using React with Lwt menhir 20230608 An LR(1) parser generator menhir-windows 20230608 An LR(1) parser generator menhirLib 20230608 Runtime support library for parsers generated by Menhir menhirLib-windows 20230608 Runtime support library for parsers generated by Menhir menhirSdk 20230608 Compile-time library for auxiliary tools related to Menhir menhirSdk-windows 20230608 Compile-time library for auxiliary tools related to Menhir merlin 4.11-414 Editor helper, provides completion, typing and source browsing in Vim and Emacs merlin-lib 4.11-414 Merlin's libraries mew 0.1.0 Modal editing witch mew_vi 0.5.0 Modal editing witch, VI interpreter num 1.4 The legacy Num library for arbitrary-precision integer and rational arithmetic num-windows 1.1 The legacy Num library for arbitrary-precision integer and rational arithmetic obelisk 0.6.0 Pretty-printing for Menhir files ocaml 4.14.1 The OCaml compiler (virtual package) ocaml-base-compiler 4.14.1 Official release 4.14.1 ocaml-compiler-libs v0.12.4 OCaml compiler libraries repackaged ocaml-compiler-libs-windows v0.12.0 OCaml compiler libraries repackaged ocaml-config 2 OCaml Switch Configuration ocaml-lsp-server 1.17.0 LSP Server for OCaml ocaml-options-vanilla 1 Ensure that OCaml is compiled with no special options enabled ocaml-syntax-shims 1.0.0 Backport new syntax to older OCaml versions ocaml-version 3.6.2 Manipulate, parse and generate OCaml compiler version strings ocaml-windows 4.14.1 A meta-package depending on any OCaml cross-compiler ocaml-windows64 4.14.1 OCaml cross-compiler for 64-bit x86 Windows targets ocaml_intrinsics v0.16.0 Intrinsics ocamlbuild 0.14.2 OCamlbuild is a build system with builtin rules to easily build most OCaml projects ocamlc-loc 3.10.0 Parse ocaml compiler output into structured form ocamlfind 1.9.6 A library manager for OCaml ocamlfind-windows 1.9.1 A library manager for OCaml ocamlformat 0.26.1 pinned to version 0.26.1 ocamlformat-lib 0.26.1 OCaml Code Formatter ocamlformat-rpc-lib 0.26.1 Auto-formatter for OCaml code (RPC mode) ocamlgraph 2.1.0 A generic graph library for OCaml ocp-indent 1.8.1 A simple tool to indent OCaml programs ocplib-endian 1.2 Optimised functions to read and write int16/32/64 from strings and bigarrays odoc 2.2.1 OCaml documentation generator odoc-parser 2.0.0 Parser for ocaml documentation comments opam-core 2.1.5 Core library for opam 2.1 opam-file-format 2.1.6 Parser and printer for the opam file syntax opam-format 2.1.5 Format library for opam 2.1 opam-installer 2.1.5 Installation of files to a prefix, following opam conventions ordering 3.10.0 Element ordering parsexp v0.16.0 S-expression parsing library parsexp-windows v0.16.0 S-expression parsing library patdiff v0.16.0 File Diff using the Patience Diff algorithm patience_diff v0.16.0 Diff library using Bram Cohen's patience diff algorithm pcre 7.5.0 Bindings to the Perl Compatibility Regular Expressions library pp 1.2.0 Pretty-printing library ppx_assert v0.16.0 Assert-like extension nodes that raise useful errors on failure ppx_assert-windows v0.16.0 Assert-like extension nodes that raise useful errors on failure ppx_base v0.16.0 Base set of ppx rewriters ppx_base-windows v0.16.0 Base set of ppx rewriters ppx_bench v0.16.0 Syntax extension for writing in-line benchmarks in ocaml code ppx_bench-windows v0.16.0 Syntax extension for writing in-line benchmarks in ocaml code ppx_bin_prot v0.16.0 Generation of bin_prot readers and writers from types ppx_bin_prot-windows v0.16.0 Generation of bin_prot readers and writers from types ppx_cold v0.16.0 Expands [@cold] into [@inline never][@specialise never][@local never] ppx_cold-windows v0.16.0 Expands [@cold] into [@inline never][@specialise never][@local never] ppx_compare v0.16.0 Generation of comparison functions from types ppx_compare-windows v0.16.0 Generation of comparison functions from types ppx_custom_printf v0.16.0 Printf-style format-strings for user-defined string conversion ppx_custom_printf-windows v0.16.0 Printf-style format-strings for user-defined string conversion ppx_derivers 1.2.1 Shared [@@deriving] plugin registry ppx_derivers-windows 1.2.1 Shared [@@deriving] plugin registry ppx_deriving 5.2.1 Type-driven code generation for OCaml ppx_deriving-windows 5.2.1 Type-driven code generation for OCaml ppx_disable_unused_warnings v0.16.0 Expands [@disable_unused_warnings] into [@warning "-20-26-32-33-34-35-36-37-38-39-60-66-67"] ppx_disable_unused_warnings-windows v0.16.0 Expands [@disable_unused_warnings] into [@warning "-20-26-32-33-34-35-36-37-38-39-60-66-67"] ppx_enumerate v0.16.0 Generate a list containing all values of a finite type ppx_enumerate-windows v0.16.0 Generate a list containing all values of a finite type ppx_expect v0.16.0 Cram like framework for OCaml ppx_expect-windows v0.16.0 Cram like framework for OCaml ppx_fields_conv v0.16.0 Generation of accessor and iteration functions for ocaml records ppx_fields_conv-windows v0.16.0 Generation of accessor and iteration functions for ocaml records ppx_fixed_literal v0.16.0 Simpler notation for fixed point literals ppx_fixed_literal-windows v0.16.0 Simpler notation for fixed point literals ppx_globalize v0.16.0 A ppx rewriter that generates functions to copy local values to the global heap ppx_globalize-windows v0.16.0 A ppx rewriter that generates functions to copy local values to the global heap ppx_hash v0.16.0 A ppx rewriter that generates hash functions from type expressions and definitions ppx_hash-windows v0.16.0 A ppx rewriter that generates hash functions from type expressions and definitions ppx_here v0.16.0 Expands [%here] into its location ppx_here-windows v0.16.0 Expands [%here] into its location ppx_ignore_instrumentation v0.16.0 Ignore Jane Street specific instrumentation extensions ppx_ignore_instrumentation-windows v0.16.0 Ignore Jane Street specific instrumentation extensions ppx_inline_test v0.16.0 Syntax extension for writing in-line tests in ocaml code ppx_inline_test-windows v0.16.0 Syntax extension for writing in-line tests in ocaml code ppx_jane v0.16.0 Standard Jane Street ppx rewriters ppx_jane-windows v0.16.0 Standard Jane Street ppx rewriters ppx_let v0.16.0 Monadic let-bindings ppx_let-windows v0.16.0 Monadic let-bindings ppx_log v0.16.0 Ppx_sexp_message-like extension nodes for lazily rendering log messages ppx_log-windows v0.16.0 Ppx_sexp_message-like extension nodes for lazily rendering log messages ppx_module_timer v0.16.0 Ppx rewriter that records top-level module startup times ppx_module_timer-windows v0.16.0 Ppx rewriter that records top-level module startup times ppx_optcomp v0.16.0 Optional compilation for OCaml ppx_optcomp-windows v0.16.0 Optional compilation for OCaml ppx_optional v0.16.0 Pattern matching on flat options ppx_optional-windows v0.16.0 Pattern matching on flat options ppx_pipebang v0.16.0 A ppx rewriter that inlines reverse application operators `|>` and `|!` ppx_pipebang-windows v0.16.0 A ppx rewriter that inlines reverse application operators `|>` and `|!` ppx_sexp_conv v0.16.0 [@@deriving] plugin to generate S-expression conversion functions ppx_sexp_conv-windows v0.16.0 [@@deriving] plugin to generate S-expression conversion functions ppx_sexp_message v0.16.0 A ppx rewriter for easy construction of s-expressions ppx_sexp_message-windows v0.16.0 A ppx rewriter for easy construction of s-expressions ppx_sexp_value v0.16.0 A ppx rewriter that simplifies building s-expressions from ocaml values ppx_sexp_value-windows v0.16.0 A ppx rewriter that simplifies building s-expressions from ocaml values ppx_stable v0.16.0 Stable types conversions generator ppx_stable-windows v0.16.0 Stable types conversions generator ppx_stable_witness v0.16.0 Ppx extension for deriving a witness that a type is intended to be stable. In this context, stable means that the serialization format will never change. This allows programs running at different versions of the code to safely communicate. ppx_stable_witness-windows v0.16.0 Ppx extension for deriving a witness that a type is intended to be stable. In this context, stable means that the serialization format will never change. This allows programs running at different versions of the code to safely communicate. ppx_string v0.16.0 Ppx extension for string interpolation ppx_string-windows v0.16.0 Ppx extension for string interpolation ppx_tydi v0.16.0 Let expressions, inferring pattern type from expression. ppx_tydi-windows v0.16.0 Let expressions, inferring pattern type from expression. ppx_typerep_conv v0.16.0 Generation of runtime types from type declarations ppx_typerep_conv-windows v0.16.0 Generation of runtime types from type declarations ppx_variants_conv v0.16.0 Generation of accessor and iteration functions for ocaml variant types ppx_variants_conv-windows v0.16.0 Generation of accessor and iteration functions for ocaml variant types ppx_yojson_conv_lib v0.16.0 Runtime lib for ppx_yojson_conv ppxlib 0.30.0 Standard infrastructure for ppx rewriters ppxlib-windows 0.29.1 Standard library for ppx rewriters re 1.11.0 RE is a regular expression library for OCaml re-windows 1.8.0 RE is a regular expression library for OCaml react 1.2.2 Declarative events and signals for OCaml result 1.5 Compatibility Result module result-windows 1.5 Compatibility Result module sedlex 3.2 An OCaml lexer generator for Unicode seq base Compatibility package for OCaml's standard iterator type starting from 4.07. seq-windows base Compatibility package for OCaml's standard iterator type starting from 4.07. sexp_pretty v0.16.0 S-expression pretty-printer sexplib v0.16.0 Library for serializing OCaml values to and from S-expressions sexplib-windows v0.16.0 Library for serializing OCaml values to and from S-expressions sexplib0 v0.16.0 Library containing the definition of S-expressions and some base converters sexplib0-windows v0.16.0 Library containing the definition of S-expressions and some base converters spawn v0.15.1 Spawning sub-processes splittable_random v0.16.0 PRNG that can be split into independent streams splittable_random-windows v0.16.0 PRNG that can be split into independent streams stdio v0.16.0 Standard IO library for OCaml stdio-windows v0.16.0 Standard IO library for OCaml stdlib-shims 0.3.0 Backport some of the new stdlib features to older compiler stdlib-shims-windows 0.3.0 Backport some of the new stdlib features to older compiler stdune 3.10.0 Dune's unstable standard library time_now v0.16.0 Reports the current time time_now-windows v0.16.0 Reports the current time timezone v0.16.0 Time-zone handling topkg 1.0.7 The transitory OCaml software packager trie 1.0.0 Strict impure trie tree typerep v0.16.0 Typerep is a library for runtime types typerep-windows v0.16.0 Typerep is a library for runtime types tyxml 4.5.0 A library for building correct HTML and SVG documents uchar 0.0.2 Compatibility library for OCaml's Uchar module utop 2.13.1 Universal toplevel for OCaml uucp 15.1.0 Unicode character properties for OCaml uunf 15.1.0 Unicode text normalization for OCaml uuseg 15.1.0 Unicode text segmentation for OCaml uutf 1.0.3 Non-blocking streaming Unicode codec for OCaml variantslib v0.16.0 Part of Jane Street's Core library variantslib-windows v0.16.0 Part of Jane Street's Core library xdg 3.10.0 XDG Base Directory Specification yojson 2.1.0 Yojson is an optimized parsing and printing library for the JSON format yojson-windows 2.1.0 Yojson is an optimized parsing and printing library for the JSON format zed 3.2.3 Abstract engine for text edition in OCaml ```

[hhugo]

@TyOverby, it seems that the code structure generated by ppx_expect defeat the logic in place inside ppx_inline_test to allow deadcode of tests. In particular, the call to Ppx_inline_test_lib.test is inside a functor Test_block.Make. It prevents Ppx_inline_test_lib.test to be inlined and prevent the arguments to Ppx_inline_test_lib.test to be collected.

[hhugo]

@WardBrian, you might want to open the issue against ppx_expect instead

[WardBrian]

@hhugo thanks for the digging! Unfortunately updating the ppx dependencies is harder for us than JSOO, so I may be stuck with the broken behavior for a while, but I'll open a ticket on their repo

[hhugo]

xref the ppx_expect issue to here. I can provide some guidance on how to fix the ppx_expect code.

[hhugo]

fixed in https://github.com/janestreet/ppx_expect/pull/56

[hhugo]

For the record, you need at least two expect tests to reproduce the issue otherwise, inlining of the functor happens and the code is properly DCE

[WardBrian]

For the record, you need at least two expect tests to reproduce the issue

Ah, that explains some of the difficulties reproducing.

Thanks for getting a fix in before I even got around to writing a new issue!