import java

import semmle.code.configfiles.ConfigFiles

import semmle.code.java.Diagnostics

// Locations should either be :0:0:0:0 locations (UnknownLocation, or

// a whole file), or all 4 fields should be positive.

Location badLocation() {

[result.getStartLine(), result.getEndLine(), result.getStartColumn(), result.getEndColumn()] != 0 and

[result.getStartLine(), result.getEndLine(), result.getStartColumn(), result.getEndColumn()] < 1

}

// The start should not be after the end.

Location backwardsLocation() {

result.getStartLine() > result.getEndLine()

or

result.getStartLine() = result.getEndLine() and

result.getStartColumn() > result.getEndColumn()

}

// Normally a location should tag at least one locatable entity.

// Note this is not absolutely necessarily a bug (it does not always indicate a location is

// an orphan in database terms), because classes that are seen both as source code and as a

// .class file are extracted using both locations, with `Top.getLocation` filtering out the

// class-file location when both a source- and a class-file location are present in the

// database. However at present the Java extractor always uses the class-file location at

// least to locate a `File`, so such a location does end up with a single use.

Location unusedLocation() {

not exists(Top t | t.getLocation() = result) and

not exists(XmlLocatable x | x.getLocation() = result) and

not exists(ConfigLocatable c | c.getLocation() = result) and

not exists(Diagnostic d | d.getLocation() = result) and

not (

result.getFile().getExtension() = "xml" and

result.getStartLine() = 0 and

result.getStartColumn() = 0 and

result.getEndLine() = 0 and

result.getEndColumn() = 0

)

}

from string reason, Location l

where

reason = "Bad location" and l = badLocation()

or

reason = "Backwards location" and l = backwardsLocation()

or

reason = "Unused location" and l = unusedLocation()

select reason, l