mk: don't build docs for internal or behind-the-facade crates in beta/stable

This saves a bunch of a time and will make distributions smaller, as well as
avoiding filling the implementors page with internal garbage. Turn it back on
with `--enable-compiler-docs` if you want compiler docs during development.

Crates behind the facade are only documented on nightly/dev builds (where they
can be used).

[breaking-change]

Closes #23772
Closes #21297

configure

@@ -526,7 +526,8 @@ VAL_OPTIONS=""
 opt valgrind 0 "run tests with valgrind (memcheck by default)"
 opt helgrind 0 "run tests with helgrind instead of memcheck"
 opt valgrind-rpass 1 "run rpass-valgrind tests with valgrind"
-opt docs     1 "build documentation"
+opt docs     1 "build standard library documentation"
+opt compiler-docs     0 "build compiler documentation"
 opt optimize 1 "build optimized rust code"
 opt optimize-cxx 1 "build optimized C++ code"
 opt optimize-llvm 1 "build optimized LLVM"

mk/crates.mk

@@ -122,17 +122,29 @@ ONLY_RLIB_rustc_bitflags := 1
 # You should not need to edit below this line
 ################################################################################
 
+# On channels where the only usable crate is std, only build documentation for
+# std. This keeps distributions small and doesn't clutter up the API docs with
+# confusing internal details from the crates behind the facade.
+
+ifeq ($(CFG_RELEASE_CHANNEL),stable)
+DOC_CRATES := std
+else
+ifeq ($(CFG_RELEASE_CHANNEL),beta)
+DOC_CRATES := std
+else
 DOC_CRATES := $(filter-out rustc, \
-              $(filter-out rustc_trans, \
-              $(filter-out rustc_typeck, \
-              $(filter-out rustc_borrowck, \
-              $(filter-out rustc_resolve, \
-              $(filter-out rustc_driver, \
-              $(filter-out rustc_privacy, \
-              $(filter-out rustc_lint, \
-              $(filter-out log, \
-              $(filter-out getopts, \
-              $(filter-out syntax, $(CRATES))))))))))))
+	   $(filter-out rustc_trans, \
+	   $(filter-out rustc_typeck, \
+	   $(filter-out rustc_borrowck, \
+	   $(filter-out rustc_resolve, \
+	   $(filter-out rustc_driver, \
+	   $(filter-out rustc_privacy, \
+	   $(filter-out rustc_lint, \
+	   $(filter-out log, \
+	   $(filter-out getopts, \
+	   $(filter-out syntax, $(CRATES))))))))))))
+endif
+endif
 COMPILER_DOC_CRATES := rustc rustc_trans rustc_borrowck rustc_resolve \
                        rustc_typeck rustc_driver syntax rustc_privacy \
                        rustc_lint

mk/docs.mk

@@ -259,7 +259,10 @@ doc/$(1)/index.html: $$(LIB_DOC_DEP_$(1)) doc/$(1)/
 endef
 
 $(foreach crate,$(DOC_CRATES),$(eval $(call DEF_LIB_DOC,$(crate),DOC_TARGETS)))
-$(foreach crate,$(COMPILER_DOC_CRATES),$(eval $(call DEF_LIB_DOC,$(crate),COMPILER_DOC_TARGETS)))
+
+ifdef CFG_COMPILER_DOCS
+  $(foreach crate,$(COMPILER_DOC_CRATES),$(eval $(call DEF_LIB_DOC,$(crate),COMPILER_DOC_TARGETS)))
+endif
 
 ifdef CFG_DISABLE_DOCS
   $(info cfg: disabling doc build (CFG_DISABLE_DOCS))