scripts/sphinx-pre-install: make it handle Sphinx versions

As we want to switch to a newer Sphinx version in the future,
add some version detected logic, checking if the current
version meets the requirement and suggesting upgrade it the
version is supported but too old.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

scripts/sphinx-pre-install

@@ -13,7 +13,7 @@ use strict;
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 
-my $virtenv_dir = "sphinx_1.4";
+my $conf = "Documentation/conf.py";
 my $requirement_file = "Documentation/sphinx/requirements.txt";
 
 #
@@ -26,7 +26,9 @@ my $need = 0;
 my $optional = 0;
 my $need_symlink = 0;
 my $need_sphinx = 0;
+my $rec_sphinx_upgrade = 0;
 my $install = "";
+my $virtenv_dir = "sphinx_";
 
 #
 # Command line arguments
@@ -201,13 +203,15 @@ sub check_missing_tex($)
 	}
 }
 
-sub check_sphinx()
+sub get_sphinx_fname()
 {
-	return if findprog("sphinx-build");
+	my $fname = "sphinx-build";
+	return $fname if findprog($fname);
 
-	if (findprog("sphinx-build-3")) {
+	$fname = "sphinx-build-3";
+	if (findprog($fname)) {
 		$need_symlink = 1;
-		return;
+		return $fname;
 	}
 
 	if ($virtualenv) {
@@ -219,6 +223,73 @@ sub check_sphinx()
 	} else {
 		add_package("python-sphinx", 0);
 	}
+
+	return "";
+}
+
+sub check_sphinx()
+{
+	my $min_version;
+	my $rec_version;
+	my $cur_version;
+
+	open IN, $conf or die "Can't open $conf";
+	while (<IN>) {
+		if (m/^\s*needs_sphinx\s*=\s*[\'\"]([\d\.]+)[\'\"]/) {
+			$min_version=$1;
+			last;
+		}
+	}
+	close IN;
+
+	die "Can't get needs_sphinx version from $conf" if (!$min_version);
+
+	open IN, $requirement_file or die "Can't open $requirement_file";
+	while (<IN>) {
+		if (m/^\s*Sphinx\s*==\s*([\d\.]+)$/) {
+			$rec_version=$1;
+			last;
+		}
+	}
+	close IN;
+
+	die "Can't get recommended sphinx version from $requirement_file" if (!$min_version);
+
+	$virtenv_dir .= $rec_version;
+
+	my $sphinx = get_sphinx_fname();
+	return if ($sphinx eq "");
+
+	open IN, "$sphinx --version 2>&1 |" or die "$sphinx returned an error";
+	while (<IN>) {
+		if (m/^\s*sphinx-build\s+([\d\.]+)$/) {
+			$cur_version=$1;
+			last;
+		}
+		# Sphinx 1.2.x uses a different format
+		if (m/^\s*Sphinx.*\s+([\d\.]+)$/) {
+			$cur_version=$1;
+			last;
+		}
+	}
+	close IN;
+
+	die "$sphinx didn't return its version" if (!$cur_version);
+
+	printf "Sphinx version %s (minimal: %s, recommended >= %s)\n",
+		$cur_version, $min_version, $rec_version;
+
+	if ($cur_version lt $min_version) {
+		print "Warning: Sphinx version should be >= $min_version\n\n";
+		$need_sphinx = 1;
+		return;
+	}
+
+	if ($cur_version lt $rec_version) {
+		print "Warning: It is recommended at least Sphinx version $rec_version.\n";
+		print "         To upgrade, use:\n\n";
+		$rec_sphinx_upgrade = 1;
+	}
 }
 
 #
@@ -540,7 +611,7 @@ sub check_needs()
 		printf "\tsudo ln -sf %s /usr/bin/sphinx-build\n\n",
 		       which("sphinx-build-3");
 	}
-	if ($need_sphinx) {
+	if ($need_sphinx || $rec_sphinx_upgrade) {
 		my $activate = "$virtenv_dir/bin/activate";
 		if (-e "$ENV{'PWD'}/$activate") {
 			printf "\nNeed to activate virtualenv with:\n";
@@ -554,7 +625,8 @@ sub check_needs()
 			printf "\t$virtualenv $virtenv_dir\n";
 			printf "\t. $activate\n";
 			printf "\tpip install -r $requirement_file\n";
-			$need++;
+
+			$need++ if (!$rec_sphinx_upgrade);
 		}
 	}
 	printf "\n";