How to show wavy underline(Error Squiggles) when word is wrong in vs code extension development

Question

When developing an extension that has syntax checking how to show the wavy underline when word typed is wrong.

As of now, my extension shows only color change when the correct word is entered. But I want to underline the error.

Ex:- If frm is entered then it should underline as 'from' is the valid keyword.

user_9937309 · Answer

You should take a look at vscode-extension-samples, there are so many useful samples as a guide. I was also struggling with this type of issue and I found code-actions-sample solved the problem in my case.