n depend & cql
TRANSCRIPT
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Agenda:• Introduction
• CQL Queries & Constraints• Quality & Metrics• Dependencies Layering & Refactoring• Code Snapshot Comparison• Code Coverage • State & Mutability• Dead Code• Optimal Encapsulation• Naming Convention• Object model• Build Process Health
• Future
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Introduction• The source code is the design: a need to reveal secrets kept in the
structure of source code:
• A need to understand the big picture with a top-down approach, no matter the size of the code base.
• A need to rationalize the architecture of software by controlling the structural complexity (graph of dependencies).
• A need to capture architectural constraints and to be advised ASAP of violation.
• A need to measure the code quality and coverage.
• A need to control the code evolution.
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CQL Queries & Constraints• Queries:
• SELECT TOP 10 METHODS ORDER BY NbLinesOfCode DESC• SELECT METHODS WHERE NbLinesOfCode > 10• SELECT METHODS WHERE IsDirectlyUsing ″System.String″• SELECT FIELDS WHERE HasAttribute
"System.ThreadStaticAttribute"
• Constraints:
• WARN IF Count > 0 IN SELECT METHODS WHERE NbLinesOfCode > 20
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Quality & Metrics
Lines Of Code (LOC) and NbILInstructions
• SELECT METHODS ORDER BY NbLinesOfCode DESC• SELECT TYPES ORDER BY NbILInstructions DESC
Logical LOC vs. Physical LOC
class Program {
static void Main() {
string str = "hello";
str.IndexOf("hello", 10, 13);
str.IndexOf(
"hello",
10,
13);
}
}
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Quality & Metrics
Volume & Comment metrics
Volume:
• SELECT ASSEMBLIES ORDER BY NbNamespaces DESC• SELECT NAMESPACES ORDER BY NbTypes DESC• SELECT TYPES ORDER BY NbMethods DESC• SELECT TYPES ORDER BY NbFields DESC
Comment:
• SELECT NAMESPACES ORDER BY NbLinesOfComment DESC
• SELECT METHODS WHERE NbLinesOfCode > 10 AND PercentageComments < 30
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Quality & Metrics
Coupling metrics
Afferant Coupling (Ca) \ Efferent Coupling (Ce)
• SELECT TYPES ORDER BY TypeCa DESC• SELECT METHODS ORDER BY MethodCe DESC• SELECT NAMESPACES ORDER BY NamespaceCa DESC
Ranking
• SELECT TYPES ORDER BY TypeRank DESC• SELECT METHODS ORDER BY MethodRank DESC
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Quality & Metrics
Cyclomatic Complexity• Cyclomatic complexity is a popular procedural software metric equal to the
number of decisions that can be taken in a procedure.
• Concretely, in C# the CC of a method is the number of following expressions found in the body of the method:
if | while | for | foreach | case | default | continue | goto | && | || | catch | ternary operator ?: | ??
• Following expressions are not counted for CC computation:
else | do | switch | try | using | throw | finally | return | object creation | method call | field access
SELECT METHODS WHERE CyclomaticComplexity > 20SELECT METHODS WHERE ILCyclomaticComplexity > 25
WARN If Count > 0 IN SELECT METHODS WHERE NbLinesOfCode > 20 AND CyclomaticComplexity > 8
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Quality & Metrics
Lack Of Cohesion Of Methods (LCOM)• Single responsibility principle: A class should not have more than one
reason to change. In such class, almost every methods access every fields.
• Lack Of Cohesion Of methods (LCOM) metric:
SELECT TYPES ORDER BY LCOM DESC
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Quality & Metrics
Others metrics
Method:• SELECT METHODS WHERE NbParameters > 5• SELECT METHODS WHERE NbVariables > 10
Field Size of Instance:• SELECT FIELDS WHERE SizeOfInst > 16
Level & Layering:• SELECT NAMESPACES ORDER BY NamespaceLevel DESC
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Dependency Layering & Refactoring
Dependency Structure Matrix (DSM)
• Browsing
• Dependencies weight
• CQL Queries generation
• ‘Box & Arrow’ graph production
• Indirect dependencies mode
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Dependency Layering & Refactoring
Impact analysis to plan Refactoring
• What if we need to replace Moco.Cecil by another framework:
– SELECT TYPES WHERE IsDirectlyUsing "ASSEMBLY:Mono.Cecil" OR IsDirectlyUsing "ASSEMBLY:Mono.Cecil.Pdb"
– ‘Box & Arrow’ graph production.
– Code impacted
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Dependency Layering & Refactoring
.NET Components: Assemblies vs. Namespace
• Assemblies: Physical – Cost at development time : poor compilation performance– Cost at deployment : more file to manage– Cost at runtime : CLR overhead per assembly basis
• Namespaces: Logical– No cycles dependencies detection– Internal visibility level
• Key to be able to use namespaces as components:Being able to control dependencies between namespaces
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Dependency Layering & Refactoring
Introduction to levelization• Central design principle:
Getting rid of dependency cycles between components
• A and B belongs to a dependency cycles: – They can’t be developed and tested independently– They are an indivisible unit– They constitute a super component
• Diseconomy of scale phenomenon: one super component costs more than several smaller components.
• Right size for a component : 500 to 2000 LOC
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Dependency Layering & Refactoring
Demo: Levelization / dependencies cycles
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Code Snapshot Comparison
Introduction to Build comparison• SELECT METHODS WHERE WasChanged OR WasAdded OR WasDeleted
• SELECT METHODS WHERE CommentsWereChanged OR VisibilityWasChanged OR CodeWasChanged
• SELECT METHODS WHERE IsUsedDifferently OR IsUsedRecently OR IsNotUsedAnymore
• SELECT METHODS WHERE IsObsolete OR BecameObsolete
– SELECT TYPES WHERE IsDirectlyUsing "ASSEMBLY:Mono.Cecil" OR IsDirectlyUsing "ASSEMBLY:Mono.Cecil.Pdb"
– ‘Box & Arrow’ graph production.
– Code impacted
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Code Snapshot Comparison
Build Comparison CQL Constraints• Force comment change:WARN IF Count > 0 IN SELECT METHODS WHERE CodeWasChanged AND !CommentsWereChanged
• API ascendant compatibility:WARN IF Count > 0 IN SELECT METHODS WHERE IsInOlderBuild AND IsPublic AND (VisibilityWasChanged OR WasRemoved)
• Interface immutability:WARN IF Count > 0 IN SELECT TYPES WHERE IsInterface AND IsPublic AND WasChanged
• Force quality on change:WARN IF Count > 0 IN SELECT METHODS WHERE (CodeWasChanged OR WasAdded) AND(NbLinesOfCode > 20 OR CyclomaticComplexity > 10 OR …)
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Code Snapshot Comparison
Build Comparison facilities
• Tier code change.
SELECT METHODS WHERE IsUsedRecentlySELECT METHODS WHERE IsNotUsedAnymore
SELECT TYPES WHERE IsUsedDifferently
SELECT NAMESPACES WHERE IsUsedDifferently
SELECT ASSEMBLIES WHERE IsUsedDifferently
• Dependency/Coupling changes.
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Code Coverage
Code Coverage Metrics
• Coverage data gathered from– VSTS 2005 & 2008– NCover 2.x
• Metrics– PercentageCoverage– NbLinesOfCodeCovered– NbLInesOfCodeNotCovered– PercentageBranchCoverage (Ncover only)
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Code Coverage
Code Coverage Facilities
• Uncoverable attributes
• Coverage file merging options:– OR– XOR– AND– NONE
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State and Mutability
State and mutability: Definition of immutable types• Immutable types: types where instances’ state cannot be modified once
created.
• A stateless type (i.e a type without any instance field) is considered as immutable.
• A type with at least one non-private instance field is considered as mutable (because such a field can be eventually modified outside the type).
• A class that derives directly or indirectly from a mutable type is considered as mutable.
• Enumeration, static type, type defined in framework assemblies and delegate classes are never considered as immutable.
• Particularly, classes that derive directly or indirectly from a class defined in a tier assembly that is not the System.Object class, is never considered as immutable.
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State and Mutability
CQL facilities for State and mutability• Ensuring that the type Namespace.Foo is immutable:
WARN IF Count != 1 IN SELECT TYPES WHERE ! IsImmutable AND FulleNameIs "Namespace.Foo"
• Matching methods that breaks immutability (i.e that modifies instance fields):SELECT METHODS FROM TYPES "Namespace.Foo" WHERE ChangesObjectState AND !IsConstructor
• Matching methods that modifies static fields:SELECT METHODS FROM TYPES "Namespace.Foo" WHERE ChangesTypeState AND !IsClassConstructor
• Matching methods that modifies a particular field:SELECT METHODS FROM TYPES "Namespace.Foo" WHERE IsDirectlyWritingField "Namespace.Foo.m_Field"
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Potentially dead codeWARN IF Count > 0 IN SELECT METHODS WHERE MethodCa == 0 AND ! IsPublic AND ! IsEntryPoint AND ! IsExplicitInterfaceImpl AND ! IsClassConstructor AND ! IsFinalizer
WARN IF Count > 0 IN SELECT FIELDS WHERE FieldCa == 0 AND ! IsPublic AND ! IsLiteral AND ! IsEnumValue AND ! NameIs "value__"
WARN IF Count > 0 IN SELECT TYPES WHERE TypeCa == 0 AND ! IsPublic AND ! NameIs "Program"
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Optimal Encapsulation
• SELECT TYPES WHERE CoulBeInternal • SELECT METHODS WHERE CoulBePrivate
• Danger: public constructor and serialization
• SELECT NAMESPACES WHERE CoulBeInternal
• Detecting usage of System.Compilers.Services.InternalsVisibleToAttributeSELECT METHODS WHERE ShouldBePublic
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Naming Conventions• Instance fields should begin with m_
WARN If Count > 0 IN
SELECT FIELDS WHERE ! NameLike "^m_" AND ! IsStatic
• Interface name should begin with I
WARN If Count > 0 IN SELECT TYPES
WHERE IsInterface AND !NameLike "^I" AND !IsNested
• Types names should begin with an upper letter:
WARN If Count > 0 IN SELECT TYPES
WHERE !NameLike "^[A-Z] "
• Exception class should be suffixed with ‘Exception’
WARN If Count > 0 IN SELECT TYPES
WHERE IsExceptionClass AND !NameLike"Exception$"
or
WHERE DeriveFrom "System.Exception"
AND !NameLike "Exception$"
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Object model
• Types that should be sealed
WARN IF Count > 0 IN SELECT TYPES WHERE IsClass AND NbChildren ==0 AND !IsSealed AND !IsStatic
• Classes that implement ‘ICompare<T>’ should be nested
WARN IF Count > 0 IN SELECT TYPES WHERE Implement "System.Collections.Generic.IComparer<T>" AND !IsNested AND !IsInFrameworkAssembly
• OO Hierarcy:
SELECT TYPES WHERE DepthOfInheritance > 6 SELECT TYPES ORDER BY NbChildren Desc
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Build Process Health• Assemblies versionning issues such as
– AssemblyA references AssemblyB v2.1 but only AssemblyB v2.0 is available.
• Assembly conflicts such as:
– Several different assemblies with the same name can be found (different = different hash code and/or different version).
• PDB files issues such as:
– Missing PDB files.
– PDB files and code source files not in-sync.
– PDB files and assemblies are not in-sync.
• Coverage files issues such as:
– Corrupted or missing coverage files.
– Coverage files and code source files not in-sync.
– Coverage files and assemblies are not in-sync.
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Future
• Enhanced Visualization (2008 Q2)
• XDepend = NDepend on Java (2008 Q3)
• Code Query Framework CQF (NDepend 3, 2008 Q3)
Writing code query and constraints with C# and LINQ
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Question?