Ant task to compare two properties files

Question

Does anyone know of an Ant task that would compare two (Java) properties files? I could not find any but I would like to be sure before I go off and implement it.

• Input: two properties files
• Output: list of property keys that are in one file but not in the other.

Just to be clear: it should perform properties-file-syntax-aware comparison, comparing the existence of keys, but ignoring the values.

Answer 1

You could try to combine a groovy ant task with the java-diff-utils library

Example

├── build.xml
├── file1.properties
└── file2.properties

Running the build produces the following output:

diff:
   [groovy] [DeleteDelta, position: 1, lines: [two=2]]
   [groovy] [InsertDelta, position: 3, lines: [threeandhalf=3.5]]
   [groovy] [ChangeDelta, position: 4, lines: [five=5] to [five=55555]]

build.xml

<project name="demo" default="diff" xmlns:ivy="antlib:org.apache.ivy.ant">

    <target name="resolve">
        <ivy:cachepath pathid="build.path">
            <dependency org="org.codehaus.groovy" name="groovy-all" rev="2.1.0-rc-1" conf="default"/>
            <dependency org="com.googlecode.java-diff-utils" name="diffutils" rev="1.2.1" conf="default"/>
        </ivy:cachepath>
    </target>

    <target name="diff" depends="resolve">
        <taskdef name="groovy" classname="org.codehaus.groovy.ant.Groovy" classpathref="build.path"/>

        <groovy>
            import difflib.*

            def original = new File("file1.properties").readLines()
            def revised  = new File("file2.properties").readLines()

            Patch patch = DiffUtils.diff(original, revised)

            patch.getDeltas().each {
                println it
            }
        </groovy>
    </target>

</project>

Notes:

• Uses Apache ivy to download dependencies

file1.properties

one=1
two=2
three=3
four=4
five=5

file2.properties

one=1
three=3
threeandhalf=3.5
four=4
five=55555

Revised Example

Returns the properties in the first file missing in the second:

diff:
   [groovy] Missing keys: [two]

build.xml

<project name="demo" default="diff" xmlns:ivy="antlib:org.apache.ivy.ant">

    <target name="resolve">
        <ivy:cachepath pathid="build.path">
            <dependency org="org.codehaus.groovy" name="groovy-all" rev="2.1.0-rc-1" conf="default"/>
        </ivy:cachepath>
    </target>

    <target name="diff" depends="resolve">
        <taskdef name="groovy" classname="org.codehaus.groovy.ant.Groovy" classpathref="build.path"/>

        <groovy>
            def source = new Properties()
            def target = new Properties()

            new File("file1.properties").withInputStream { source.load(it) }
            new File("file2.properties").withInputStream { target.load(it) }

            def diff = source.findResults { k,v ->
                k in target ? null : k
            }

            println "Missing keys: ${diff}"
        </groovy>
    </target>

</project>