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CPD (Copy/Paste Detector)¶

Java by default, suitable for anything (groovy, jsp, simple text etc.) | Home | Plugin

CPD support activates only when de.aaschmid.cpd gradle plugin applied manually:

plugins {        
    id 'de.aaschmid.cpd' version '3.1'
    id 'ru.vyarus.quality' version '4.2.0'
}

CPD is a part of PMD project and so there is no need for additional version configuration (pmd version used).

Note

Special xsl file used for manual html report generation because plugin does not support html report. This is official pmd style, but modified to show all duplicates (original script shows only duplicates > 30 lines).

Output¶

2 java duplicates were found by CPD

sample.cpd.(OtherStruct1.java:3)  [16 lines / 75 tokens]
sample.cpd.(OtherStruct2.java:3)
  │
 3│    public class OtherStruct1 {
 4│    
 5│        public static void main(String[] args) {
 6│            Math.sqrt(12);
 7│            Math.sqrt(12);
 8│            Math.sqrt(12);
 9│            Math.sqrt(12);
10│            Math.sqrt(12);
11│            Math.sqrt(12);
12│            Math.sqrt(12);
13│            Math.sqrt(12);
14│            Math.sqrt(12);
15│            Math.sqrt(12);
16│        }
17│    
18│        public void differentMethod1() {

Shows all files with duplicate parts and source sample from the first file.

Note

Order of files may vary on different environments and so you may see sources from different files in the resulted report. It doesn't matter much, just don't be surprised.

Warning

Tool does not search for exact matches, instead it tries to find very common blocks: for example, some code block could be copied and slightly modified and cpd will be able to match it.

Config¶

Config options with defaults:

quality {
    cpd = true // false to disable plugin configuration
    cpdUnifySources = true // false to not modify cpdCheck task sources
}

Note

CPD itself may be configured with plugin's cpd closure

Configurations applied by plugin:

cpd {
    toolVersion = quality.pmdVersion
    ignoreFailures = !extension.strict
}

If only groovy sources available, then cpd.language automatically set to groovy (but only if cpd task declared in the same module with quality plugin!).

Cpd tasks¶

In contrast to other quality tools CPD plugin registers only one task cpdCheck instead of task per source set (otherwise it would be impossible to find duplicates between source sets or even between different modules).

By default, cpdCheck task configured to check all available source sets. But quality plugin will modify chpdCheck.source:

All files from source sets, not configured for quality checks (quality.sourceSets) are removed. This way cpd scope is unified with other quality plugins scope.
Global excludes are also applied.

Source modifications could be disabled with quality.cpdUnifySources = false

If multiple cpd tasks would be registered (other tasks declared manually), sources would be modified only for default cpdCheck task. But console reporting and HTML report will be added for all tasks. Also, all cpd tasks would be disabled with quality.enabled = false

Note

By default, CPD configured for java sources check. To change target language use:

cpd {
    language = 'groovy'
}

Warning

CPD will try to check all files in enabled source sets. For example, if you have both java and groovy sources in main source set then CPD will try to check both and, most likely, will fail with groovy parse error (as language is java by default).

To solve such cases either manually exclude additional sources:

cpdCheck.exclude '*.groovy'

Or split check in multiple tasks, where each task checks only one language (see below),

Multiple file types support¶

If you need to check more than one type of files (for example, java and groovy sources), you'll need to configure separate tasks per each required type. For example:

cpdCheck.exclude '*.groovy'                     

task groovyCpdCheck(type:de.aaschmid.gradle.plugins.cpd.Cpd) {
    language = 'groovy'
    source = sourceSets.main.allGroovy 
}

Here groovy sources excluded from default cpdCheck task (because cpd plugin by default covers all source sets). Now the default task will search duplicates only in java files (and only within sources configured in quality plugin).

New task declared for searching groovy duplicates (groovyCpdCheck).

Both tasks will be assigned to check, so by calling gradlew check you'll run both checks. Console report will be shown for both tasks (and HTML reports generated).

Note that task language will be also mentioned in console report:

:check
:cpdCheck
2 java duplicates were found by CPD
...

:groovyCpdCheck
2 groovy duplicates were found by CPD
...

Tip

CPD understands many source languages. But if specified language cannot be found, a fallback mechanism uses net.sourceforge.pmd.cpd.AnyLanguage instead. This fallback language does not run ANTLR and therefore also checks duplicates in comments.

This way you can use cpd for searching for duplicates even in pure text files, web templates or other resources.

Multi-module projects¶

For multi-module projects, it is recommended to apply cpd plugin in the root project. This way only one cpdCheck task is created (in the root project), which will check sources from all modules (it's the only way to find duplicates between different modules).

But quality plugin, should be applied on module level (because all other quality tasks are source set scoped).

Expected root project configuration looks like this:

plugins {
    id 'de.aaschmid.cpd' version '3.1'
    id 'ru.vyarus.quality' version '4.2.0' apply false
}
cpd {
    // cpd configuration, if required
}

// possibly other cpd tasks 

subprojects {
    apply plugin: 'java'
    apply plugin: 'ru.vyarus.quality'

    quality {
        // plugin configuration, if required    
    }   
}

This way each module have its own quality plugin, but quality configuration is the same in all modules.

Quality plugin will detect cpd plugin in the root project and configure it the same way as in single module case. But as quality plugin will apply in each module, only first configured module will apply cpd modifications of toolVersion and ignoreFailures (assuming this settings are the same for all modules).

Each module will exclude cpdCheck task sources, not covered by quality plugin configuration. For example, if only main source set configured, each module will exclude test sources. This way, each module control sources only related to its module and overall cpdCheck sources configuration would be correct.

Each module will attach all root project's cpd tasks to its check (sub module's check depend on root project tasks). Imagine if you work in one module you may call check only on module level. With common quality tasks its clear - all configured module's source sets must be validated. But you may introduce duplicates (e.g. copied method from other module) and the only way to detect it is to call root project tasks (so its completely logical to assign root cpd check to module checks).

As an example, suppose we have 2 modules mod1 and mod2 with root project configuration as described above:

root project's cpd plugin will be configured
mod1 will exclude mod1/src/test/java from crpCheck.sources
:mod1:check depends on :cpdCheck
mod2 will exclude mod2/src/test/java from crpCheck.sources
:mod2:check depends on :cpdCheck

You will also notice, that in the multi-module setup console output will identify class module:

mod1/sample.cpd.(OtherStruct1.java:3)  [16 lines / 75 tokens]
mod2/sample.cpd.(OtherStruct2.java:3)
  │
 3│    public class OtherStruct1 {
 4│    
 5│        public static void main(String[] args) {
 6│            Math.sqrt(12);

Tip

Quality plugin actually search CPD plugin not in the root-most project but in entire parent chain. So if you have complex gradle project and cpd plugin declared somewhere in the middle of projects hierarchy, everything will still be properly configured.

Suppress¶

CPD violations could be suppressed only for some languages (Java, C/C++, Dart, Go, Javascript, Kotlin, Lua, Matlab, Objective-C, PL/SQL, Python and Swift) with comments containing CPD-OFF and CPD-ON:

public Object someParameterizedFactoryMethod(int x) throws Exception {
    // some unignored code

    // tell cpd to start ignoring code - CPD-OFF

    // mission critical code, manually loop unroll
    goDoSomethingAwesome(x + x / 2);
    goDoSomethingAwesome(x + x / 2);
    goDoSomethingAwesome(x + x / 2);
    goDoSomethingAwesome(x + x / 2);
    goDoSomethingAwesome(x + x / 2);
    goDoSomethingAwesome(x + x / 2);

    // resume CPD analysis - CPD-ON

    // further code will *not* be ignored
}

Java sources could be also suppressed with annotations:

//enable suppression
@SuppressWarnings("CPD-START")
public Object someParameterizedFactoryMethod(int x) throws Exception {
    // any code here will be ignored for the duplication detection
}

//disable suppression
@SuppressWarnings("CPD-END)
public void nextMethod() {
}