Use the system GAP

build/pkgs/gap/distros/debian.txt

@@ -1 +1,2 @@
+gap
 libgap-dev

build/pkgs/gap/distros/fedora.txt

@@ -0,0 +1,5 @@
+gap
+gap-core
+gap-devel
+gap-libs
+libgap

build/pkgs/gap/spkg-configure.m4

@@ -0,0 +1,96 @@
+SAGE_SPKG_CONFIGURE([gap], [
+  # Default to installing the SPKG, if the check is run at all.
+  sage_spkg_install_gap=yes
+
+  m4_pushdef([GAP_MINVER],["4.12.2"])
+
+  SAGE_SPKG_DEPCHECK([ncurses readline zlib], [
+    AC_PATH_PROG(GAP, gap)
+    AS_IF([test -n "${GAP}"], [
+      AC_MSG_CHECKING([for gap version GAP_MINVER or newer])
+
+      # GAP will later add the "user" path to the list of root paths
+      # so long as we don't initialize GAP with -r in Sage. But we
+      # don't want to include it in the hard-coded list.
+      GAPRUN="${GAP} -r -q --bare --nointeract -c"
+      _cmd='Display(GAPInfo.KernelInfo.KERNEL_VERSION);'
+      GAP_VERSION=$( ${GAPRUN} "${_cmd}" 2>/dev/null )
+      AX_COMPARE_VERSION(["${GAP_VERSION}"], [ge], [GAP_MINVER], [
+        AC_MSG_RESULT([yes])
+        AC_MSG_CHECKING([for gap root paths])
+        _cmd='Display(JoinStringsWithSeparator(GAPInfo.RootPaths,";"));'
+        SYS_GAP_ROOT_PATHS=$( ${GAPRUN} "${_cmd}" 2>/dev/null )
+        AC_MSG_RESULT([$SYS_GAP_ROOT_PATHS])
+        AS_IF([test -n "${SYS_GAP_ROOT_PATHS}"], [
+          AC_MSG_CHECKING([for the PrimGrp, SmallGrp, and TransGrp packages])
+          # Check for a very minimal set of packages without which the
+          # sage test suite will fail. The crazy thing below is a
+          # "quadrigraph" for a square bracket.
+          _cmd="Display(@<:@"
+          _cmd="${_cmd} TestPackageAvailability(\"PrimGrp\"),"
+          _cmd="${_cmd} TestPackageAvailability(\"SmallGrp\"),"
+          _cmd="${_cmd} TestPackageAvailability(\"TransGrp\")"
+          _cmd="${_cmd} @:>@);"
+          _output=$( ${GAPRUN} "${_cmd}" 2>/dev/null )
+          AS_IF([test $? -eq 0], [
+            AS_CASE([$_output],
+              [*fail*],[AC_MSG_RESULT([no (at least one package missing)])],[
+                # default case, i.e. no "fail"
+                AC_MSG_RESULT([yes])
+
+                AC_MSG_CHECKING([if we can link against libgap])
+                # That was all for the CLI. Now we check for libgap,
+                # too. There's a long list of headers we need in
+                # src/sage/libs/gap/gap_includes.pxd, but libgap-api.h
+                # combined with the version test above should be
+                # sufficient even on systems where the headers are
+                # packaged separately.
+                _old_libs=$LIBS
+                LIBS="${LIBS} -lgap"
+                AC_LANG_PUSH([C])
+                AC_LINK_IFELSE([
+                  AC_LANG_PROGRAM(
+                    [[#include <gap/libgap-api.h>]],
+                    [[
+                      int main(int argc, char** argv) {
+                        GAP_Initialize(0, 0, 0, 0, 0);
+                        return 0;
+                      }
+                    ]])
+                ],[
+                  AC_MSG_RESULT([yes])
+                  sage_spkg_install_gap=no
+                ],[
+                  AC_MSG_RESULT([no])
+                ])
+                AC_LANG_POP
+                LIBS="${_old_libs}"
+            ])
+          ], [
+            # The gap command itself failed
+            AC_MSG_RESULT([no (package check command failed)])
+          ])
+        ])
+      ],[
+        # Version too old
+        AC_MSG_RESULT([no])
+      ])
+    ])
+  ])
+
+  m4_popdef([GAP_MINVER])
+],[],[],[
+  # This is the post-check phase, where we make sage-conf
+  # substitutions, in this case of GAP_ROOT_PATHS. We begin with the
+  # two root paths used by the sage distribution. The '${prefix}' is
+  # a magic string that sage-conf will replace.
+  GAP_ROOT_PATHS='${prefix}/lib/gap;${prefix}/share/gap';
+
+  AS_IF([test "${sage_spkg_install_gap}" = "no"],[
+    # If we're using the system GAP, append the system root
+    # paths to the existing two sage paths.
+    GAP_ROOT_PATHS="${GAP_ROOT_PATHS};${SYS_GAP_ROOT_PATHS}"
+  ])
+
+  AC_SUBST(GAP_ROOT_PATHS, "${GAP_ROOT_PATHS}")
+])

build/pkgs/gap/spkg-install.in

@@ -16,46 +16,43 @@ if [ "$SAGE_DEBUG" = yes ] ; then
     export CFLAGS="-O0 -g3 -DDEBUG_MASTERPOINTERS -DDEBUG_GLOBAL_BAGS -DDEBUG_FUNCTIONS_BAGS $CFLAGS"
 fi
 
-# LDFLAGS hack below needed by Semigroups package
-sdh_configure $SAGE_CONFIGURE_GMP LDFLAGS="-pthread" --prefix=$SAGE_LOCAL
+sdh_configure $SAGE_CONFIGURE_GMP --prefix=$SAGE_LOCAL
 sdh_make
-
 sdh_make_install
-# sdh_make install-headers install-libgap
-# The 'packagemanager' package expects this https://github.com/gap-packages/PackageManager/issues/105
-mkdir -p "$SAGE_LOCAL/lib/gap/bin"
 
 # Install only the minimal packages GAP needs to run
 sdh_install pkg/gapdoc pkg/primgrp pkg/smallgrp pkg/transgrp "$GAP_ROOT"/pkg
 
-# Install additional packages that are not strictly required, but that are
-# typically "expected" to be loaded: These are the default packages that are
-# autoloaded at GAP startup (via the PackagesToLoad UserPreference) with an
-# out-of-the-box GAP installation; see
-# https://github.com/sagemath/sage/issues/22626#comment:393 for discussion on this
-#
-# Also include atlasrep which is a dependency of tomlib
+# Install additional packages that are automatically loaded in the
+# default GAP configuration. The list can be found in lib/package.gi
+# as part of the "PackagesToLoad" user preference. Also include
+# atlasrep because it is a dependency of tomlib.
 sdh_install \
+    pkg/alnuth \
     pkg/atlasrep \
-    pkg/autodoc \
     pkg/autpgrp \
-    pkg/alnuth \
     pkg/crisp \
     pkg/ctbllib \
     pkg/factint \
     pkg/fga \
     pkg/irredsol \
     pkg/laguna \
-    pkg/packagemanager \
     pkg/polenta \
     pkg/polycyclic \
-    pkg/radiroot \
     pkg/resclasses \
     pkg/sophus \
     pkg/tomlib \
-    pkg/utils \
     "$GAP_ROOT"/pkg
 
+# Finally, install packagemanager for the people who reject both
+# sage's and their system's package managers. We have to create
+# the local bin directory first:
+#
+#   https://github.com/gap-packages/PackageManager/issues/105
+#
+mkdir -p "$SAGE_LOCAL/lib/gap/bin"
+sdh_install pkg/packagemanager "$GAP_ROOT"/pkg
+
 # TODO: This seems unnecessary--we are already installing all of doc/ to
 # GAP_ROOT, which is necessary for some functionality in GAP to work.  Do
 # we need this?  Maybe doc/gap could just be a symlink to gap/doc??

build/pkgs/gap_packages/SPKG.rst

@@ -7,6 +7,20 @@ Description
 Several "official" and "undeposited" GAP packages available from
 https://www.gap-system.org/Packages/packages.html
 
+Installing this SPKG will install the corresponding GAP packages, but
+before you can use them in Sage, they still have to be loaded into
+either the GAP interface or libgap::
+
+  sage: gap.eval('LoadPackage("Grape")')  # optional - gap_packages
+  'true'
+  sage: libgap.LoadPackage("Grape")       # optional - gap_packages
+  true
+
+Those correspond to::
+
+  gap> LoadPackage("Grape");
+
+within the GAP interface and libgap, respectively.
 
 Upstream Contact
 ----------------

build/pkgs/gap_packages/spkg-install.in

@@ -1,5 +1,34 @@
-GAP_ROOT="$SAGE_LOCAL/lib/gap"
-PKG_DIR="$GAP_ROOT/pkg"
+# Ask GAP for the directory where sysinfo.gap lives. This is to
+# support system GAP installations. This root-path gathering
+# command is borrowed from gap's spkg-configure.m4 and modified
+# to separate the paths with spaces.
+GAPRUN="gap -r -q --bare --nointeract -c"
+_cmd='Display(JoinStringsWithSeparator(GAPInfo.RootPaths," "));'
+GAP_ROOT_PATHS=$(${GAPRUN} "${_cmd}")
+
+# Loop though GAP_ROOT_PATHS looking for sysinfo.gap
+GAP_ROOT=""
+for grp in $GAP_ROOT_PATHS; do
+    if [ -f "${grp}/sysinfo.gap" ]; then
+        GAP_ROOT=$grp
+        echo "found GAP root $GAP_ROOT"
+        break
+    fi
+done
+
+# Try the old sage default if nothing else worked.
+if [ -z "$GAP_ROOT" ]; then
+    GAP_ROOT="$SAGE_LOCAL/lib/gap"
+    echo "falling back to GAP root $GAP_ROOT"
+fi
+
+# And finally, throw an error ASAP if the build is going to fail anyway.
+if [ ! -f "${GAP_ROOT}/sysinfo.gap" ]; then
+    sdh_die "no sysinfo.gap in your gap root"
+fi
+
+# Where to install these packages
+PKG_DIR="$SAGE_LOCAL/lib/gap/pkg"
 
 PKG_SRC_DIR="$(pwd)/src/pkg"
 cd "$PKG_SRC_DIR"
@@ -12,6 +41,7 @@ cd "$PKG_SRC_DIR"
 
 sdh_install \
     aclib \
+    autodoc \
     corelg \
     crime \
     cryst \
@@ -31,11 +61,13 @@ sdh_install \
     polymaking \
     qpa \
     quagroup \
+    radiroot \
     repsn \
     singular \
     sla \
     sonata \
     toric \
+    utils \
     "$PKG_DIR"
 
 install_compiled_pkg()

pkgs/sage-conf/_sage_conf/_conf.py.in

@@ -9,6 +9,11 @@ VERSION = "@PACKAGE_VERSION@"
 SAGE_LOCAL = "@prefix@"
 SAGE_ROOT = "@SAGE_ROOT@"
 
+# The semicolon-separated list of GAP root paths. This is the list of
+# locations that are searched for GAP packages. This is passed directly
+# to GAP via the -l flag.
+GAP_ROOT_PATHS = "@GAP_ROOT_PATHS@".replace('${prefix}', SAGE_LOCAL)
+
 # The path to the standalone maxima executable.
 MAXIMA = "@SAGE_MAXIMA@".replace('${prefix}', SAGE_LOCAL)
 

src/bin/sage

@@ -628,7 +628,9 @@ fi
 
 if [ "$1" = '-gap' -o "$1" = '--gap' ]; then
     shift
-    exec gap "$@"
+    # Use "-A" to avoid warnings about missing packages. The gap
+    # interface and libgap within sage both already do this.
+    exec gap -A "$@"
 fi
 
 if [ "$1" = '-gap3' -o "$1" = '--gap3' ]; then

src/doc/en/constructions/groups.rst

@@ -180,8 +180,8 @@ Here's another way, working more directly with GAP::
     sage: print(gap.eval("normal := NormalSubgroups( G )"))
     [ Alt( [ 1 .. 5 ] ), Group(()) ]
     sage: G = gap.new("DihedralGroup( 10 )")
-    sage: G.NormalSubgroups()
-    [ Group( [ f1, f2 ] ), Group( [ f2 ] ), Group( <identity> of ... ) ]
+    sage: G.NormalSubgroups().SortedList()
+    [ Group( <identity> of ... ), Group( [ f2 ] ), Group( [ f1, f2 ] ) ]
     sage: print(gap.eval("G := SymmetricGroup( 4 )"))
     Sym( [ 1 .. 4 ] )
     sage: print(gap.eval("normal := NormalSubgroups( G );"))

src/doc/en/prep/Quickstarts/Abstract-Algebra.rst

@@ -83,15 +83,13 @@ rather than just a list of numbers.  This can be very powerful.
 
 ::
 
-    sage: for K in D.normal_subgroups():
+    sage: len(D.normal_subgroups())
+    7
+    sage: for K in sorted(D.normal_subgroups()):
     ....:     print(K)
-    Subgroup generated by [(1,2,3,4,5,6,7,8), (1,8)(2,7)(3,6)(4,5)] of (Dihedral group of order 16 as a permutation group)
-    Subgroup generated by [(1,2,3,4,5,6,7,8), (1,3,5,7)(2,4,6,8), (1,5)(2,6)(3,7)(4,8)] of (Dihedral group of order 16 as a permutation group)
-    Subgroup generated by [(1,3,5,7)(2,4,6,8), (1,5)(2,6)(3,7)(4,8), (1,8)(2,7)(3,6)(4,5)] of (Dihedral group of order 16 as a permutation group)
-    Subgroup generated by [(2,8)(3,7)(4,6), (1,3,5,7)(2,4,6,8), (1,5)(2,6)(3,7)(4,8)] of (Dihedral group of order 16 as a permutation group)
-    Subgroup generated by [(1,3,5,7)(2,4,6,8), (1,5)(2,6)(3,7)(4,8)] of (Dihedral group of order 16 as a permutation group)
-    Subgroup generated by [(1,5)(2,6)(3,7)(4,8)] of (Dihedral group of order 16 as a permutation group)
     Subgroup generated by [()] of (Dihedral group of order 16 as a permutation group)
+    ...
+    Subgroup generated by [(1,2,3,4,5,6,7,8), (1,8)(2,7)(3,6)(4,5)] of (Dihedral group of order 16 as a permutation group)
 
 We can access specific subgroups if we know the generators as a
 permutation group.

src/sage/env.py

@@ -198,8 +198,7 @@ def var(key: str, *fallbacks: Optional[str], force: bool = False) -> Optional[st
 GRAPHS_DATA_DIR = var("GRAPHS_DATA_DIR", join(SAGE_SHARE, "graphs"))
 ELLCURVE_DATA_DIR = var("ELLCURVE_DATA_DIR", join(SAGE_SHARE, "ellcurves"))
 POLYTOPE_DATA_DIR = var("POLYTOPE_DATA_DIR", join(SAGE_SHARE, "reflexive_polytopes"))
-GAP_LIB_DIR = var("GAP_LIB_DIR", join(SAGE_LOCAL, "lib", "gap"))
-GAP_SHARE_DIR = var("GAP_SHARE_DIR", join(SAGE_SHARE, "gap"))
+
 COMBINATORIAL_DESIGN_DATA_DIR = var("COMBINATORIAL_DESIGN_DATA_DIR", join(SAGE_SHARE, "combinatorial_designs"))
 CREMONA_MINI_DATA_DIR = var("CREMONA_MINI_DATA_DIR", join(SAGE_SHARE, "cremona"))
 CREMONA_LARGE_DATA_DIR = var("CREMONA_LARGE_DATA_DIR", join(SAGE_SHARE, "cremona"))
@@ -243,11 +242,13 @@ def var(key: str, *fallbacks: Optional[str], force: bool = False) -> Optional[st
 # GAP memory and args
 
 SAGE_GAP_MEMORY = var('SAGE_GAP_MEMORY', None)
-_gap_cmd = "gap -r"
-if SAGE_GAP_MEMORY is not None:
-    _gap_cmd += " -s " + SAGE_GAP_MEMORY + " -o " + SAGE_GAP_MEMORY
-SAGE_GAP_COMMAND = var('SAGE_GAP_COMMAND', _gap_cmd)
+SAGE_GAP_COMMAND = var('SAGE_GAP_COMMAND', None)
 
+# The semicolon-separated search path for GAP packages. It is passed
+# directly to GAP via the -l flag.
+GAP_ROOT_PATHS = var("GAP_ROOT_PATHS",
+                     ";".join([join(SAGE_LOCAL, "lib", "gap"),
+                               join(SAGE_LOCAL, "share", "gap")]))
 
 # post process
 if DOT_SAGE is not None and ' ' in DOT_SAGE:

src/sage/ext_data/gap/sage.g

@@ -134,3 +134,17 @@ end;
 #
 # LogTo("/tmp/gapsage.log");
 #
+
+
+# Load the GAP packages that GAP itself tries to autoload in the
+# default configuration (see "PackagesToLoad" in lib/package.gi). The
+# combination of passing -A to gap and these LoadPackage statements
+# allows us to load the usual set of packages, but only if they are
+# installed. So most people will get exactly the default behavior,
+# but minimal installations won't throw warnings and fail tests.
+_autoloads := [ "autpgrp", "alnuth", "crisp", "ctbllib", "factint", "fga",
+                "irredsol", "laguna", "polenta", "polycyclic", "resclasses",
+                "sophus", "tomlib" ];
+for p in _autoloads do
+  LoadPackage(p);
+od;