\documentclass[10pt,a4paper,french]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lipsum}
\makeatletter
\def\iinput#1{%
  \marginpar{#1}%
  \InputIfFileExists{#1}{}%
  {\filename@parse{#1}%
   \edef\reserved@a{\noexpand\@missingfileerror
     {\filename@area\filename@base}%
     {\ifx\filename@ext\relax tex\else\filename@ext\fi}}%
   \reserved@a}}
\makeatother
\begin{document}
\iinput{ssdoc1.tex}
\iinput{ssdoc2.tex}
\end{document}