rustdoc: add --deny-doctest-warnings option

[pshc]

Collaboration with @rylev! Addresses #20787.

We kind of brute forced this flag into the call path for maketest, so we're soliciting better designs 👊

Also, we're wondering if we should turn this into a generic -D option, like @brson was saying. What would that look like? Would we have to implement all four flags (W, A, D, F)?

[rust-highfive]

r? @nikomatsakis

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[brson]

Do you mind trying to turn this on for the in-tree doc tests as well? It looks like these are the lines to edit:

• rust/mk/tests.mk

  Line 818 in 7541f82

  $$(call TEST_OK_FILE,$(1),$(2),$(3),doc-$(4)): $$(DOCTESTDEP_$(1)_$(2)_$(3)_$(4))

• rust/mk/tests.mk

  Line 857 in 7541f82

  $$(RUSTDOC_$(1)_T_$(2)_H_$(3)) --test --cfg dox \

There's a chance that with the current state of the tree there will be a great number of warnings. If so we'll have to decide how to deal with them. make check-docs NO_MKFILE_DEPS=1 will run the doc tests quickly without rebuilding the whole tree because of the makefile change.

[brson]

@alexcrichton What do you think of this command-line flag and having to support it indefinitely?

[pshc]

I'll give it a shot!

[pshc]

It is done. 🎐

[alexcrichton]

Would it be possible to use the same -D foo syntax that the compiler uses? That way this would actually just be rustdoc -D warnings ... and would mirror the compiler well (plus setting different various levels).

The options would have to be documented, however, as only applying to doctests rather than documentation in general.

[pshc]

@alexcrichton Sure thing.

[pshc]

@alexcrichton Oh, I didn't notice you said "options" the first time. Should I just hardcode -D warnings, or also provide -F and -A and -W?

[alexcrichton]

I would probably add flags for all of -A, -F, -W, and -D to rustdoc and then our build system can pass -D warnings by default.

[alexcrichton]

Closing due to inactivity, but feel free to reopen with a rebase!