Steps to reproduce:
1. download project and open scene
2. open "broken.shadergraph"
3. select custom function node and remove "//" (see picture attached below)
4. save asset
5. In project, select "broken.shadergraph"
6. In inspector, click "compile and show code"
7. observe errors printed below "compile and show code" button
8. go back to custom function node and add "//" at start of second line
9. save asset
10. observe errors clear from below "compile and show code"
11. In project, unselect and select "broken.shadergraph"
12. In inspector, observe errors are displayed under "compile and show code"

Expected: errors do not appear in Inspector UI when selecting asset any time after fixing code
Actual: error appears in Inspector UI after reselecting asset

Reproduces: 2019.3.0b8 (7eb5456f98b4), 2020.1.0a8 (a932f1074310)

Note: this behaviour is the same without step 6 (saving asset is trigger the issue)
Note: these errors can only cleared by removing library folder

This is a UI issue - the errors do not actually break anything or block the user. The only impact is some confusion about whether there are errors.