new loplugin:constfields

look for fields which are only assigned to in the constructor, so they
can be made const

Change-Id: I0b76817c2181227b04f6a29d6a808f5e31999765
Reviewed-on: https://gerrit.libreoffice.org/60393
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

compilerplugins/clang/constfields.py

@@ -0,0 +1,95 @@
+#!/usr/bin/python
+
+import sys
+import re
+import io
+
+definitionSet = set()
+definitionToSourceLocationMap = dict()
+definitionToTypeMap = dict()
+writeFromOutsideConstructorSet = set()
+
+# clang does not always use exactly the same numbers in the type-parameter vars it generates
+# so I need to substitute them to ensure we can match correctly.
+normalizeTypeParamsRegex = re.compile(r"type-parameter-\d+-\d+")
+def normalizeTypeParams( line ):
+    return normalizeTypeParamsRegex.sub("type-parameter-?-?", line)
+
+def parseFieldInfo( tokens ):
+    if len(tokens) == 3:
+        return (normalizeTypeParams(tokens[1]), tokens[2])
+    else:
+        return (normalizeTypeParams(tokens[1]), "")
+
+with io.open("workdir/loplugin.constfields.log", "rb", buffering=1024*1024) as txt:
+    for line in txt:
+        tokens = line.strip().split("\t")
+        if tokens[0] == "definition:":
+            access = tokens[1]
+            fieldInfo = (normalizeTypeParams(tokens[2]), tokens[3])
+            srcLoc = tokens[5]
+            # ignore external source code
+            if (srcLoc.startswith("external/")):
+                continue
+            # ignore build folder
+            if (srcLoc.startswith("workdir/")):
+                continue
+            definitionSet.add(fieldInfo)
+            definitionToTypeMap[fieldInfo] = tokens[4]
+            definitionToSourceLocationMap[fieldInfo] = tokens[5]
+        elif tokens[0] == "write-outside-constructor:":
+            writeFromOutsideConstructorSet.add(parseFieldInfo(tokens))
+        else:
+            print( "unknown line: " + line)
+
+# Invert the definitionToSourceLocationMap
+# If we see more than one method at the same sourceLocation, it's being autogenerated as part of a template
+# and we should just ignore it
+sourceLocationToDefinitionMap = {}
+for k, v in definitionToSourceLocationMap.iteritems():
+    sourceLocationToDefinitionMap[v] = sourceLocationToDefinitionMap.get(v, [])
+    sourceLocationToDefinitionMap[v].append(k)
+for k, definitions in sourceLocationToDefinitionMap.iteritems():
+    if len(definitions) > 1:
+        for d in definitions:
+            definitionSet.remove(d)
+
+# Calculate can-be-const-field set
+canBeConstFieldSet = set()
+for d in definitionSet:
+    if d in writeFromOutsideConstructorSet:
+        continue
+    srcLoc = definitionToSourceLocationMap[d];
+    fieldType = definitionToTypeMap[d]
+    if fieldType.startswith("const "):
+        continue
+    if "std::unique_ptr" in fieldType:
+        continue
+    if "std::shared_ptr" in fieldType:
+        continue
+    if "Reference<" in fieldType:
+        continue
+    if "VclPtr<" in fieldType:
+        continue
+    if "osl::Mutex" in fieldType:
+        continue
+    if "::sfx2::sidebar::ControllerItem" in fieldType:
+        continue
+    canBeConstFieldSet.add((d[0] + " " + d[1] + " " + fieldType, srcLoc))
+
+
+# sort the results using a "natural order" so sequences like [item1,item2,item10] sort nicely
+def natural_sort_key(s, _nsre=re.compile('([0-9]+)')):
+    return [int(text) if text.isdigit() else text.lower()
+            for text in re.split(_nsre, s)]
+
+# sort results by name and line number
+tmp6list = sorted(canBeConstFieldSet, key=lambda v: natural_sort_key(v[1]))
+
+# print out the results
+with open("compilerplugins/clang/constfields.results", "wt") as f:
+    for t in tmp6list:
+        f.write( t[1] + "\n" )
+        f.write( "    " + t[0] + "\n" )
+
+