[processing] Allow algorithms to specify tags

Tags are used while searching in the toolbox. This should help with
finding algorithms when the exact name is not known, eg
you could search for "envelope" or "bounds" and find the
'Polygon from Layer Extent' algorithm.

At the moment it's quite hard to discover algorithms which exist
when you don't know what their called and have to instead search
for every possible naming variant which could exist...

python/plugins/processing/algs/qgis/ExtentFromLayer.py

@@ -54,6 +54,7 @@ def getIcon(self):
     def defineCharacteristics(self):
         self.name, self.i18n_name = self.trAlgorithm('Polygon from layer extent')
         self.group, self.i18n_group = self.trAlgorithm('Vector general tools')
+        self.tags = self.tr('extent,envelope,bounds,bounding,boundary,layer')
 
         self.addParameter(ParameterVector(self.INPUT_LAYER,
                                           self.tr('Input layer')))

python/plugins/processing/algs/qgis/MergeLines.py

@@ -51,6 +51,7 @@ def getIcon(self):
     def defineCharacteristics(self):
         self.name, self.i18n_name = self.trAlgorithm('Merge lines')
         self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
+        self.tags = self.tr('line,merge,join,parts')
 
         self.addParameter(ParameterVector(self.INPUT_LAYER,
                                           self.tr('Input layer'), [dataobjects.TYPE_VECTOR_LINE]))

python/plugins/processing/core/GeoAlgorithm.py

@@ -64,6 +64,9 @@ def __init__(self):
         self.name, self.i18n_name = '', ''
         self.group, self.i18n_group = '', ''
 
+        # Tags
+        self.tags = ''
+
         # The crs taken from input layers (if possible), and used when
         # loading output layers
         self.crs = None

python/plugins/processing/gui/ProcessingToolbox.py

@@ -141,6 +141,7 @@ def _filterItem(self, item, text):
             item_text = [item.text(0).lower(), item.data(0, Qt.UserRole).lower()]
             if isinstance(item, TreeAlgorithmItem):
                 item_text.append(item.alg.commandLineName())
+                item_text.extend(item.data(0, Qt.UserRole + 1))
 
             hide = bool(text) and not all(
                 any(part in t for t in item_text)
@@ -355,6 +356,7 @@ def __init__(self, alg):
         self.setToolTip(0, name)
         self.setText(0, name)
         self.setData(0, Qt.UserRole, nameEn)
+        self.setData(0, Qt.UserRole + 1, alg.tags.split(','))
 
 
 class TreeActionItem(QTreeWidgetItem):

python/plugins/processing/modeler/ModelerDialog.py

@@ -472,6 +472,7 @@ def fillAlgorithmTree(self):
     def fillAlgorithmTreeUsingProviders(self):
         self.algorithmTree.clear()
         text = str(self.searchBox.text())
+        search_strings = text.split(' ')
         allAlgs = algList.algs
         for providerName in list(allAlgs.keys()):
             name = 'ACTIVATE_' + providerName.upper().replace(' ', '_')
@@ -486,7 +487,15 @@ def fillAlgorithmTreeUsingProviders(self):
                     continue
                 if alg.commandLineName() == self.alg.commandLineName():
                     continue
-                if text == '' or text.lower() in alg.name.lower():
+
+                item_text = [alg.name.lower()]
+                item_text.extend(alg.tags.split(','))
+
+                show = not search_strings or all(
+                    any(part in t for t in item_text)
+                    for part in search_strings)
+
+                if show:
                     if alg.group in groups:
                         groupItem = groups[alg.group]
                     else: