In regard to 1 John 1:7, believers were (past tense) once/formerly darkness but are now light in the Lord and we are to walk as children of light. (Ephesians 5:8) *Walking in darkness is descriptive of children of the devil. Walking in the light is 'descriptive' of children of God.
Only those who are saved/believers are in the light.
Acts 26:18 - to open their eyes, in order to turn them from darkness to light, and from the power of Satan to God, that they may receive forgiveness of sins and an inheritance among those who are sanctified by faith in Me.
2 Corinthians 6:14 - Do not be unequally yoked together with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness?
1 Thessalonians 5:4 - But you, brethren, are not in darkness, so that this Day should overtake you as a thief.
1 John 1:6 - If we say that we have fellowship with Him, and walk in darkness, we lie and do not practice the truth. But if we walk in the light as He is in the light, we have fellowship with one another, and the blood of Jesus Christ His Son cleanses us from all sin.
In 1 John 2:9, we read - He who says he is in the light, and hates his brother, is in darkness until now. In vs. 11 - But he who hates his brother is in darkness and walks in darkness, and does not know where he is going, because the darkness has blinded his eyes.
*Compare with 1 John 3:10 - In this the children of God and the children of the devil are manifest: Whoever does not practice righteousness is not of God, (compare with 1 John 1:6 - does not practice the truth) nor is he who does not love his brother.
*Notice that walks in darkness, hates his brother is 'descriptive' of children of the devil.
1 ohn 3:7 - Little children, make sure no one deceives you; the one who practices righteousness is righteous, just as He is righteous;
Those who practice righteousness do so BECAUSE they are righteous and not in order to become righteous. Works-salvationists and eternal IN-securists confuse 'descriptive' passages of scripture with 'prescriptive' passages and the end result is works-righteousness.