[gnome-shell/wip/hadess/welcome-tour: 1/2] util: Add a GNOME version comparison function

[Bastien Nocera <hadess src gnome org>]

commit 5cf03be7b4f8ab8d8ab329fd893184db570b3b42
Author: Bastien Nocera <hadess hadess net>
Date:   Thu Feb 4 12:26:15 2021 +0100

    util: Add a GNOME version comparison function
    
    Add a function that can compare GNOME versions, including the new naming
    scheme for GNOME 40 and later.
    
    Used in https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3632

 js/misc/util.js              | 59 +++++++++++++++++++++++++++++++++++++++++++-
 tests/meson.build            |  2 +-
 tests/unit/versionCompare.js | 49 ++++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+), 2 deletions(-)
---
diff --git a/js/misc/util.js b/js/misc/util.js
index 2da489bbe6..9bcf6fe817 100644
--- a/js/misc/util.js
+++ b/js/misc/util.js
@@ -1,7 +1,7 @@
 // -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
 /* exported findUrls, spawn, spawnCommandLine, spawnApp, trySpawnCommandLine,
             formatTime, formatTimeSpan, createTimeLabel, insertSorted,
-            ensureActorVisibleInScrollView, wiggle, lerp */
+            ensureActorVisibleInScrollView, wiggle, lerp, GNOMEversionCompare */
 
 const { Clutter, Gio, GLib, Shell, St, GnomeDesktop } = imports.gi;
 const Gettext = imports.gettext;
@@ -439,3 +439,60 @@ function wiggle(actor, params) {
 function lerp(start, end, progress) {
     return start + progress * (end - start);
 }
+
+// _zeroPadArray:
+// @array: the array to pad
+// @len: the total length to pad to
+//
+// Pad the array with '0' elements, to simplify
+// version comparison with versions with a different
+// number of elements
+function _zeroPadArray(array, len) {
+    for (let i = array.length; i < len; i++)
+        array[i] = '0';
+}
+
+// _GNOMEversionToNumber:
+// @version: a GNOME version element
+//
+// Like Number() but returns sortable values for special-cases
+// 'alpha' and 'beta'. Returns NaN for unhandled 'versions'.
+function _GNOMEversionToNumber(version) {
+    let ret = Number(version);
+    if (!isNaN(ret))
+        return ret;
+    if (version === 'alpha')
+        return -2;
+    if (version === 'beta')
+        return -1;
+    return ret;
+}
+
+// GNOMEversionCompare:
+// @version1: a string containing a GNOME version
+// @version2: a string containing another GNOME version
+//
+// Returns an integer less than, equal to, or greater than
+// zero, if version1 is older, equal or newer than version2
+function GNOMEversionCompare(version1, version2) {
+    const v1Array = version1.split('.');
+    const v2Array = version2.split('.');
+
+    if (v1Array.length !== v2Array.length) {
+        if (v1Array.length > v2Array.length)
+            _zeroPadArray(v2Array, v1Array.length);
+        else
+            _zeroPadArray(v1Array, v2Array.length);
+    }
+
+    for (let i = 0; i < v1Array.length; i++) {
+        let elemV1 = _GNOMEversionToNumber(v1Array[i]);
+        let elemV2 = _GNOMEversionToNumber(v2Array[i]);
+        if (elemV1 < elemV2)
+            return -1;
+        if (elemV1 > elemV2)
+            return 1;
+    }
+
+    return 0;
+}
diff --git a/tests/meson.build b/tests/meson.build
index 1e84f423ca..c0431631f0 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -10,7 +10,7 @@ run_test = configure_file(
 testenv = environment()
 testenv.set('GSETTINGS_SCHEMA_DIR', join_paths(meson.build_root(), 'data'))
 
-foreach test : ['insertSorted', 'jsParse', 'markup', 'params', 'url']
+foreach test : ['insertSorted', 'jsParse', 'markup', 'params', 'url', 'versionCompare']
   test(test, run_test,
     args: 'unit/@0@.js'.format(test),
     env: testenv,
diff --git a/tests/unit/versionCompare.js b/tests/unit/versionCompare.js
new file mode 100644
index 0000000000..e45f533e24
--- /dev/null
+++ b/tests/unit/versionCompare.js
@@ -0,0 +1,49 @@
+// -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
+
+// Test cases for version comparison
+
+const JsUnit = imports.jsUnit;
+
+const Environment = imports.ui.environment;
+Environment.init();
+
+const Util = imports.misc.util;
+
+const tests = [
+    { v1: '40',
+      v2: '40',
+      res: 0 },
+    { v1: '40',
+      v2: '42',
+      res: -1 },
+    { v1: '42',
+      v2: '40',
+      res: 1 },
+    { v1: '3.38.0',
+      v2: '40',
+      res: -1 },
+    { v1: '40',
+      v2: '3.38.0',
+      res: 1 },
+    { v1: '40',
+      v2: '3.38.0',
+      res: 1 },
+    { v1: '40.alpha.1.1',
+      v2: '40',
+      res: -1 },
+    { v1: '40.beta',
+      v2: '40',
+      res: -1 },
+    { v1: '40.1',
+      v2: '40',
+      res: 1 },
+    { v1: '',
+      v2: '40.alpha',
+      res: -1 },
+];
+
+for (let i = 0; i < tests.length; i++) {
+    print ('Test #' + i + ' v1: ' + tests[i].v1 + ', v2: ' + tests[i].v2);
+    JsUnit.assertEquals('Test #' + i + ' v1: ' + tests[i].v1 + ', v2: ' + tests[i].v2,
+        Util.GNOMEversionCompare (tests[i].v1, tests[i].v2), tests[i].res);
+}