PlatformIO is built on top of the open-source software construction tool called SCons. SCons has many useful command-line options that control its behavior and may come in handy to know the exact internal processes happening in SCons when it builds a target. For example:
--dry-run configures SCons to print the commands that would be executed to build
any target, but do not execute the commands.
--tree=all forces SCons to print file dependency tree including implicit and
ignored dependencies
--debug=explain will print an explanation of why SCons decides to (re-)build the
targets it selects for building.
The list of available command-line options can be found in the official SCons documentation.
The easiest way to pass extra command-line options to the SCons build system used in
PlatformIO is via the external SCONSFLAGS environment variable:
# POSIX shell
export SCONSFLAGS="--tree=all"
# Windows CMD
C:\Users\foo> set SCONSFLAGS=--dry-run