Java: Improve Android app detection

[owen-mc]

This change improves the detection of Android apps in the CodeQL Java standard library. It moves the detection of Android apps to one place and updates the detection to be more accurate. Previously we just required the presence of a AndroidManifest.xml file anywhere in the project. This PR improves that in two ways:

• the AndroidManifest.xml file must define an activity, service or content provider (so it corresponds to an android application rather than a library);
• we only consider files in an android application if they are under a folder that contains such an AndroidManifest.xml.

These are the results for "Android missing certificate pinning" which are removed by this change. I have spot-checked them and they seemed valid.

[smowton]

Suggested tidying, otherwise looks good to me

[smowton]

Suggested change

	* The predicate `isAndroid` from the module `semmle.code.java.security.AndroidCertificatePinningQuery` has been deprecated. Use `semmle.code.java.frameworks.android.Android::inAndroidApplication(File file)` instead.
	* The predicate `isAndroid` from the module `semmle.code.java.security.AndroidCertificatePinningQuery` has been deprecated. Use `semmle.code.java.frameworks.android.Android::inAndroidApplication(File)` instead.

[smowton]

Suggested change

	/**
	* There is an android manifest file which defines an activity, service or
	* content provider (so it corresponds to an android application rather than a
	* library), and `file` is in a subfolder of the folder that contains it.
	*/
	predicate inAndroidApplication(File file) {
	file.isSourceFile() and
	exists(AndroidComponentXmlElement acxe, AndroidManifestXmlFile amxf |
	amxf.getManifestElement().getApplicationElement().getAComponentElement() = acxe and
	(
	acxe instanceof AndroidActivityXmlElement or
	acxe instanceof AndroidServiceXmlElement or
	acxe instanceof AndroidProviderXmlElement
	)
	|
	file.getParentContainer+() = amxf.getParentContainer()
	)
	}
	/**
	* Holds if `amxf` defines at least one activity, service or contest provider,
	* and so it corresponds to an android application rather than a library.
	*/
	private predicate definesAndroidApplication(AndroidManifestXmlFile amxf) {
	exists(AndroidComponentXmlElement acxe |
	amxf.getManifestElement().getApplicationElement().getAComponentElement() = acxe and
	(
	acxe instanceof AndroidActivityXmlElement or
	acxe instanceof AndroidServiceXmlElement or
	acxe instanceof AndroidProviderXmlElement
	)
	)
	}
	/**
	* Holds if in `file`'s directory or some parent directory there is an `AndroidManifestXmlFile`
	* that defines at least one activity, service or contest provider, suggesting this file is
	* part of an android application.
	*/
	predicate inAndroidApplication(File file) {
	file.isSourceFile() and
	exists(AndroidManifestXmlFile amxf, Folder amxfDir |
	definesAndroidApplication(amxf) and amxfDir = amxf.getParentContainer()
	|
	file.getParentContainer+() = amxfDir
	)
	}

[smowton]

(rewords the comment to use Holds if, and splits it into two predicates)

[owen-mc]

@smowton Thanks, I've accepted those, except that I made definesAndroidApplication a (public) member predicate of AndroidManifestXmlFile. I feel like that functionality might be useful in future, and belongs more in that class.

[smowton]

LGTM (one typo)