addBefore method
Inserts newSource
before the named relativeSourceName
in the list.
Throws if the referenced source is not found or if the names are equal.
Example:
sources.addBefore('env', MapPropertySource('fallback', {...}));
Implementation
void addBefore(String relativeSourceName, PropertySource newSource) {
_assertLegalRelativeAddition(relativeSourceName, newSource);
synchronized(_sources, () {
_removeIfPresent(newSource);
int index = _assertPresentAndGetIndex(relativeSourceName);
_addAtIndex(index, newSource);
});
}