Why does sourcing a file alter the paths in the exported environment variables?

Question

I have a file .foo.sh that only contain exports, i.e.

export foo="../../../../"
export bar="a/b/c/d/"
export baz="a/b/c/d/e/f"

In a script this file is sourced like this (I have verified that it isn't something else in the script affecting it, with a test script that does only this):

!#/bin/bash
cd u/v/x/y/z/
source .foo.sh

But the environment variables are set incorrectly. If I add echo "foo $foo bar $bar baz $baz" before and after sourcing, I get this output:

foo  bar  baz 
foo . bar .. baz ../e/f

If I add cat .foo.sh so that the script looks like this:

!#/bin/bash
cd u/v/x/y/z/
cat .foo.sh
echo "foo $foo bar $bar baz $baz"
source .foo.sh
echo "foo $foo bar $bar baz $baz"

I get this output:

export foo="../../../../"
export bar="a/b/c/d/"
export baz="a/b/c/d/e/f"
foo  bar  baz 
foo . bar .. baz ../e/f

If I replace the source line with the .foo.sh contents, like this:

!#/bin/bash
cd u/v/x/y/z/
echo "foo $foo bar $bar baz $baz"
export foo="../../../../"
export bar="a/b/c/d/"
export baz="a/b/c/d/e/f"
echo "foo $foo bar $bar baz $baz"

I get this output:

foo  bar  baz 
foo ../../../../ bar a/b/c/d/ baz a/b/c/d/e/f

Why are the paths changed to be relative to another directory when exported in a sourced file, compared to when just exported inline, even though the sourced file is in the CWD and the exported paths are hardcoded strings?

Answer 1

There was a file named .foo.sh in a directory listed in my PATH, that exported the same variables, but with other values. Turns out, just like running a normal command, when sourcing a file the shell first looks in the PATH for a file with a matching name. This is extra confusing considering which .foo.sh doesn't return anything, like it would for an executable file. But changing the script to source like this source ./.foo.sh fixed the issue.