CDRIVER-4680 Remove ENABLE_ICU option and related code

[joshbsiegel]

Summary

This PR will remove any references to the now unused ICU dependency.

Background

#1317 implemented SASLprep natively, removing the need for the heavyweight and sometimes problematic ICU library. As such, we can remove all code related to this library, which will allow users to have sha-256 encryption without downloading an external dependency.

What's New

• Removed all ICU related variables and logic in various CMakeLists.txt
• Removed all ICU references in the Evergreen scripts
• Removed all ICU related logic (#ifdefs) in the driver
• Removed all ICU related tests

[rcsanchez97]

So, we vendor the RPM spec file, and as a result we avoid directly modifying it. The correct way to modify it for our builds is to carry the desired changes in spec.patch. I recommend that you make the following changes (to restore the spec file and then move your proposed changes to the patch):

diff --git a/.evergreen/etc/mongo-c-driver.spec b/.evergreen/etc/mongo-c-driver.spec
index aec5a5010..230b4fc11 100644
--- a/.evergreen/etc/mongo-c-driver.spec
+++ b/.evergreen/etc/mongo-c-driver.spec
@@ -37,6 +37,7 @@ BuildRequires: openssl-devel
 BuildRequires: pkgconfig(libsasl2)
 BuildRequires: pkgconfig(zlib)
 BuildRequires: pkgconfig(snappy)
+BuildRequires: pkgconfig(icu-uc)
 BuildRequires: pkgconfig(libzstd)
 %if %{with tests}
 BuildRequires: mongodb-server
@@ -122,6 +123,7 @@ Documentation: http://mongoc.org/libbson/%{version}/
     -DENABLE_SSL:STRING=OPENSSL \
     -DENABLE_SASL:STRING=CYRUS \
     -DENABLE_MONGODB_AWS_AUTH:STRING=ON \
+    -DENABLE_ICU:STRING=ON \
     -DENABLE_AUTOMATIC_INIT_AND_CLEANUP:BOOL=OFF \
     -DENABLE_CRYPTO_SYSTEM_PROFILE:BOOL=ON \
     -DENABLE_MAN_PAGES:BOOL=ON \
diff --git a/.evergreen/etc/spec.patch b/.evergreen/etc/spec.patch
index 18fe23281..ee110274c 100644
--- a/.evergreen/etc/spec.patch
+++ b/.evergreen/etc/spec.patch
@@ -1,6 +1,6 @@
---- mongo-c-driver.spec.orig   2021-11-04 16:34:50.350572049 -0400
-+++ mongo-c-driver.spec        2021-11-04 16:37:54.962271319 -0400
-@@ -10,17 +10,17 @@
+--- mongo-c-driver.spec.orig   2023-07-17 14:42:52.236247070 -0400
++++ mongo-c-driver.spec        2023-07-17 14:43:16.572305452 -0400
+@@ -10,7 +10,7 @@
  %global gh_project   mongo-c-driver
  %global libname      libmongoc
  %global libver       1.0
@@ -9,9 +9,7 @@
  #global up_prever    rc0
  # disabled as require a MongoDB server
  %bcond_with          tests
- 
- # disable for bootstrap (libmongocrypt needs libbson)
- %bcond_without       libmongocrypt
+@@ -20,7 +20,7 @@
  
  Name:      mongo-c-driver
  Summary:   Client library written in C for MongoDB
@@ -20,3 +18,19 @@
  Release:   1%{?dist}
  # See THIRD_PARTY_NOTICES
  License:   Apache-2.0 AND ISC AND MIT AND Zlib
+@@ -37,7 +37,6 @@
+ BuildRequires: pkgconfig(libsasl2)
+ BuildRequires: pkgconfig(zlib)
+ BuildRequires: pkgconfig(snappy)
+-BuildRequires: pkgconfig(icu-uc)
+ BuildRequires: pkgconfig(libzstd)
+ %if %{with tests}
+ BuildRequires: mongodb-server
+@@ -123,7 +122,6 @@
+     -DENABLE_SSL:STRING=OPENSSL \
+     -DENABLE_SASL:STRING=CYRUS \
+     -DENABLE_MONGODB_AWS_AUTH:STRING=ON \
+-    -DENABLE_ICU:STRING=ON \
+     -DENABLE_AUTOMATIC_INIT_AND_CLEANUP:BOOL=OFF \
+     -DENABLE_CRYPTO_SYSTEM_PROFILE:BOOL=ON \
+     -DENABLE_MAN_PAGES:BOOL=ON \

Additionally, I recommend emailing the RPM maintainer, Remi, whenever the next release is made that incorporates this change (I'm guessing that will be 1.25.0) to let him know that ICU stuff can be dropped. You could also include the changes that you are proposing to the spec file in this PR.

[kevinAlbs]

Additionally, I recommend emailing the RPM maintainer, Remi, whenever the next release is made that incorporates this change (I'm guessing that will be 1.25.0) to let him know that ICU stuff can be dropped. You could also include the changes that you are proposing to the spec file in this PR.

I suggest adding this to the top of the NEWS file to serve as a reminder for the 1.25.0 release. The 1.25.0 release is not yet planned:

libmongoc 1.25.0 (Unreleased)
=============================

Improvements:

  * Remove optional dependency of libicu.

[rcsanchez97]

LGTM

[kevinAlbs]

Remove these paragraphs from authentication.rst:

Passwords for SCRAM-SHA-256 undergo the preprocessing step known as SASLPrep
specified in `RFC 4013 <https://tools.ietf.org/html/rfc4013>`_. SASLPrep will
only be performed for passwords containing non-ASCII characters.  SASLPrep
requires libicu. If libicu is not available, attempting to authenticate over
SCRAM-SHA-256 with non-ASCII passwords will result in error.

Usernames *never* undergo SASLPrep.

By default, when building the C driver libicu is linked if available. This can
be changed with the ``ENABLE_ICU`` cmake option. To specify an installation
path of libicu, specify ``ICU_ROOT`` as a cmake option. See the
`FindICU <https://cmake.org/cmake/help/v3.7/module/FindICU.html>`_ documentation
for more information.

Since libicu is no longer a concern to users, I think mention of SASLPrep is unnecessary.