entrypoint.sh: better messages for incorrect inputs for the action

Github Action editor automatically generates a template based on
the meta data from action.yml. However, it passes empty strings
to optional inputs regardless their default values.

To remedy the issue, provide better messages and auto reset compiler
and args inputs if both of them are empty.

Fixes #16.

.github/workflows/test.yml

@@ -39,6 +39,22 @@ jobs:
           working_directory: test/
           compiler: arara
           args: "--verbose"
+      # https://github.com/xu-cheng/latex-action/issues/16
+      - name: Test Action with Github Default Template
+        uses: ./
+        with:
+          # The root LaTeX file to be compiled
+          root_file: test/test.tex
+          # The working directory for the LaTeX engine
+          working_directory: # optional
+          # The LaTeX engine to be invoked
+          compiler: # optional, default is latexmk
+          # Extra arguments to be passed to the LaTeX engine
+          args: # optional, default is -pdf -file-line-error -interaction=nonstopmode
+          # [Deprecated] Install extra packages by tlmgr
+          extra_packages: # optional
+          # Install extra packages by apk
+          extra_system_packages: # optional
       - name: Check pdf files
         run: |
           file test/test.pdf | grep -q ' PDF '

entrypoint.sh

@@ -2,13 +2,32 @@
 
 set -e
 
+warn() {
+  echo "::warning :: $1"
+}
+
+error() {
+  echo "::error :: $1"
+  exit 1
+}
+
 root_file="$1"
 working_directory="$2"
 compiler="$3"
 args="$4"
 extra_packages="$5"
 extra_system_packages="$6"
 
+if [ -z "$root_file" ]; then
+  error "Input 'root_file' is missing."
+fi
+
+if [ -z "$compiler" ] && [ -z "$args" ]; then
+  warn "Input 'compiler' and 'args' are both empty. Reset them to default values."
+  compiler="latexmk"
+  args="-pdf -file-line-error -interaction=nonstopmode"
+fi
+
 if [ -n "$extra_system_packages" ]; then
   for pkg in $extra_system_packages; do
     echo "Install $pkg by apk"
@@ -17,12 +36,16 @@ if [ -n "$extra_system_packages" ]; then
 fi
 
 if [ -n "$extra_packages" ]; then
-  echo "::warning ::Input 'extra_packages' is deprecated. We now build LaTeX document with full TeXLive installed."
+  warn "Input 'extra_packages' is deprecated. We now build LaTeX document with full TeXLive installed."
 fi
 
 if [ -n "$working_directory" ]; then
   cd "$working_directory"
 fi
 
+if [ ! -f "$root_file" ]; then
+  error "File '$root_file' cannot be found from the directory '$PWD'."
+fi
+
 # shellcheck disable=SC2086
 "$compiler" $args "$root_file"