Seems like a good thing to add.

Do we make this a special variable in GN or a function (like cmake_minimum_required in CMake)?

cmake_minimium_version controls the min cmake version, not the min ninja version.

gn should just hardcode the ninja version it requires (1.5 or when pools were added).

The simplest (and bad) way seems to hard code it (like Meson, but the fact it does is irrelevant).

https://chromium-review.googlesource.com/546475

The reference to cmake_minimu_version was just about the syntax. I know it controls the version of CMake :)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/188307cee04070a6164db1c31aa06de7d0290ae6

commit 188307cee04070a6164db1c31aa06de7d0290ae6
Author: Thiago Farina <tfarina@chromium.org>
Date: Mon Jun 26 23:49:23 2017

tools/gn: write out the required version of ninja

Write to the build.ninja file the required version of Ninja
to avoid problems like the one that happended in
https://groups.google.com/a/chromium.org/d/msgid/chromium-dev/CAMGbLiFsmWqyHnriH3eFB%2BmQ_CXs1qSTKSaP4fv3GQYf3Zr63Q%40mail.gmail.com?utm_medium=email&utm_source=footer

BUG= 732518 

Change-Id: Ief55a93798de15fa5fae0b74db6ab7c4c844e5aa
Reviewed-on: https://chromium-review.googlesource.com/546475
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Thiago Farina <tfarina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#482469}
[modify] https://crrev.com/188307cee04070a6164db1c31aa06de7d0290ae6/tools/gn/ninja_build_writer.cc

Thanks for the fix. However, the person on the thread was using 1.3.4, so requiring 1.1.0 probably isn't enough; gn must depend on something newer.

I was thinking the same thing and waiting for you to comment on the review, but you didn't.

Pools were added at 1.1.0. 1.5 is fine by you Nico? Otherwise let me know which version you want to be picked.

I was neither cc'd nor listed as reviewer on the review, so I wonder how you think I should've commented on it :-)

The mail mentions "ninja: error: toolchain.ninja:1292: unknown pool name". Looking at around that line in my local toolchain.ninja, it has

  pool = console

Console pools were added in 1.5.1 (https://groups.google.com/forum/#!topic/ninja-build/3DLt4mC4e1Y/discussion), so at least that.

Other options: Pools didn't work quite right before 1.6.0 (https://github.com/ninja-build/ninja/issues/959), so maybe 1.6.0.

And since using anything older than what's in depot_tools is incorrect, using 1.7.2 would be an option too.

Because I posted a link to the review at comment #5, but let's move on :)

I will copy it there this time, so you can comment/review if you want.

The mail mentions "ninja: error: toolchain.ninja:1292: unknown pool name".

My preference is for 1.7.2, for the reasons you outlined here, so I picked
that.

https://chromium-review.googlesource.com/550077

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4a581dfb4b77eda8fb98b6434a325dec7ff00417

commit 4a581dfb4b77eda8fb98b6434a325dec7ff00417
Author: Thiago Farina <tfarina@chromium.org>
Date: Fri Jun 30 02:45:41 2017

tools/gn: require a newer version of ninja

Requiring 1.1.0 is not enough because console pools are needed,
and it was added only in 1.5.1.

But pools did not work quite right until 1.6.0, but since using
anything other than what is in depot_tools currently is not
correct, and the current version of ninja binary there is 1.7.2,
picked that one now.

BUG= 732518 

Change-Id: I7b4af6f16166145fb88255d2ad6018a07d0569c8
Reviewed-on: https://chromium-review.googlesource.com/550077
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Thiago Farina <tfarina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#483600}
[modify] https://crrev.com/4a581dfb4b77eda8fb98b6434a325dec7ff00417/tools/gn/ninja_build_writer.cc