Doc: document findlib interaction (#1323)

manual/linker.wiki

@@ -2,23 +2,19 @@
 The Js_of_ocaml compiler accepts JavaScript files provided on the command-line.
 The main purpose is to provide (external) primitives needed by the bytecode program.
 
-Most of the primitives from the standard library are already implemented and loaded by default (located in "runtime.js").
+Most of the primitives from the standard library are already implemented and loaded by default.
 
-Additionally, some other primitives are installed but not loaded by default:
- * "+toplevel.js" : when compiling toplevel
+Additionally, some other primitives are available but not loaded by default:
+ * "+toplevel.js" and "+dynlink.js" when compiling toplevel and/or using dynlink.
 
 == Command-line
 Pass the JavaScript file (must have a ".js" extension)
 <<code |
 js_of_ocaml jsfile.js a.byte
 >>
 
-Or load it from a findlib package
-<<code |
-js_of_ocaml +mypackage/jsfile.js a.byte
->>
-The file **jsfile.js** will be looked up inside **mypackage** lib directory.
-When no package is provided, the compiler will look inside js_of_ocaml-compiler lib directory.
+See the <<a_manual chapter="runtime-files" |runtime files>> chapter for how to
+discover runtime files.
 
 == Provide your own JavaScript
 You may need to provide extra JavaScript files to provide missing primitives or to override existing ones.

manual/menu.wiki

@@ -21,6 +21,7 @@
 ==[[tailcall|About tailcall optimization]]
 
 =Misc
+==[[runtime-files|How to look up runtime files]]
 ==[[debug|How to debug a program]]
 ==[[contribute|How to contribute]]
 ==[[performances|Performances]]

manual/overview.wiki

@@ -47,7 +47,7 @@ For alternatives, see <<a_manual chapter="install" |Install>>.
 
 === with ocamlbuild and oasis ===
   Js_of_ocaml also provide an ocamlbuild plugin.
-  See <<a_api subproject="js_of_ocaml-ocamlbuild"|module Ocamlbuild_js_of_ocaml>>.
+  See [[https://github.com/ocsigen/js_of_ocaml-ocamlbuild/blob/master/ocamlbuild_js_of_ocaml.mli|js_of_ocaml-ocamlbuild>>.
 
 === with dune ===
   Dune has native support for js_of_ocaml.

manual/runtime-files.wiki

@@ -0,0 +1,115 @@
+= Runtime files =
+
+For compiling a bytecode executable to JavaScript, one often need to pass
+JavaScript runtime files for some OCaml libraries used by the
+executable. Tracking the required runtime files is done using the de-facto
+standard for library management in OCaml, Findlib.
+
+
+== Listing js runtime files
+
+To list all JavaScript runtime files for a set of libraries:
+
+{{{
+  ocamlfind query -format "%+(jsoo_runtime)" -r LIB1 LIB2 ... | grep -v "^$"
+}}}
+
+For example, for **base** and **time_now**
+
+{{{
+  $ ocamlfind query -format "%+(jsoo_runtime)" -r base time_now | grep -v "^$"
+  ~/.opam/4.14.0/lib/base/base_internalhash_types/runtime.js
+  ~/.opam/4.14.0/lib/base/runtime.js
+  ~/.opam/4.14.0/lib/time_now/runtime.js
+}}}
+
+Here is minimal example of manually compiling a single ml file program:
+{{{
+  $ export LIBS=base,time_now
+  $ ocamlfind ocamlc -package $LIBS -linkpkg main.ml -o main.byte
+  $ js_of_ocaml $(ocamlfind query -format "%+(jsoo_runtime)" -r $LIBS) main.byte
+}}}
+
+== Declaring runtime JavaScript files inside a META file
+
+The **jsoo_runtime** variable is used to declare one or more runtime files.
+Files must be coma-separated and should be plain names relative to the package directory.
+
+For example, to declare that **mypackage.sublib** requires the file **mypackage/subdir/runtime.js**
+{{{
+  cat mypackage/META
+  package "sublib" (
+    directory = "subdir"
+    jsoo_runtime = "runtime.js"
+  )
+}}}
+
+While the mechanism allows arbitrary naming for the javascript files,
+if there is only one file, we suggest naming it **runtime.js** by
+convention.
+
+== The old deprecated way
+
+Before dune and its native support for js_of_ocaml, the (hacky) way
+to rely on Findlib was to use a **linkopts** variable with a **javascript**
+predicate {{{linkopts(javascript)}}} and have js_of_ocaml be responsible for
+looking up the files in the right directory.
+
+This approach is not very satisfying:
+* It makes it harder for a build system to know the set of dependencies.
+* The js_of_ocaml compiler needs to perform findlib resolution itself.
+
+=== Listing linkopts
+
+To list all {{{linkopts(javascript)}}} for a set of libraries:
+
+{{{
+  ocamlfind query -o-format -r -predicates javascript LIB1 LIB2 ...
+}}}
+
+For example, for **base** and **time_now**
+
+{{{
+  $ ocamlfind query -o-format -r -predicates javascript base time_now
+  +base/base_internalhash_types/runtime.js
+  +base/runtime.js
+  +time_now/runtime.js
+}}}
+
+=== Declaring runtime JavaScript files inside META files
+
+The content of {{{linkopts(javascript)}}} is given directly to the
+js_of_ocaml compiler.  To be able reference files independently of the
+installation path, we rely on js_of_ocaml's findlib support (see Command-Line findlib support below).
+
+For example, to declare that **mypackage.sublib** requires the file **mypackage/subdir/runtime.js**
+
+{{{
+  cat mypackage/META
+  package "sublib" (
+    directory = "subdir"
+    linkopts(javascript) = "+mypackage/sublib/runtime.js"
+  )
+}}}
+
+== Command line findlib support (deprecated)
+If js_of_ocaml is compiled with findlib support, one can use the
+following syntax to reference JavaScript files:
+* {{{ +{findlib-package}/{javascript-file} }}}
+* {{{ +{javascript-file} }}}
+
+The file **javascript-file** will be looked up inside the **findlib-package** lib directory.
+
+When no package is provided, the compiler will look inside js_of_ocaml-compiler lib directory.
+
+For example, if findlib install all libraries inside ${LIBDIR}:
+* {{{+mypackage/jsfile.js}}} resolves to {{{${LIBDIR}/mypackage/jsfile.js}}}
+* {{{+mypackage/dir/jsfile.js}}} resolves to {{{${LIBDIR}/mypackage/dir/jsfile.js}}}
+* {{{+toplevel.js}}} resolves to {{{${LIBDIR}/js_of_ocaml-compiler/jsfile.js}}}
+
+== Compatibility
+
+**dune** generate META files that are usable with the old deprecated
+way.  However, it only uses **jsoo_runtime** to look up information.
+
+**js_of_ocaml-ocamlbuild** uses **jsoo_runtime** by default starting with version 5.0.

manual/separate-compilation.wiki

@@ -38,19 +38,8 @@ Additional runtime files are sometime needed and can be passed on the
 command line.  In particular, some packages/libraries come with their
 own runtime file.
 
-As an example, compiling a program that has a dependency on {{{base}}}
-will require the {{{runtime.js}}}} file provided by base.
-
-{{{
-js_of_ocaml --runtime-only -o my-runtime.js PATH_TO_BASE_LIB/runtime.js dummy
-}}}
-
-If js_of_ocaml is compiled with findlib support, one can also use the
-following syntax {{{ +{findlib-package}/{javascript-file} }}}.
-
-{{{
-js_of_ocaml --runtime-only -o my-runtime.js +base/runtime.js dummy
-}}}
+See the <<a_manual chapter="runtime-files" |runtime files>> chapter for how to
+discover these files.
 
 === 2. Build compilation units