nitj: improve Ant cache by not rewritting unchanged file

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>

diff --git a/src/compiler/java_compiler.nit b/src/compiler/java_compiler.nit
index 3da2a81..c229f88 100644 (file)
--- a/src/compiler/java_compiler.nit
+++ b/src/compiler/java_compiler.nit
@@ -90,14 +90,32 @@ redef class ModelBuilder
        fun write_java_files(compiler: JavaCompiler): Array[String] do
                var jfiles = new Array[String]
                for f in compiler.files do
-                       var file = new FileWriter.open("{compiler.compile_dir}/{f.filename}")
+                       var filepath = "{compiler.compile_dir}/{f.filename}"
+                       var file = cache_file(filepath)
                        for line in f.lines do file.write(line)
-                       file.close
+                       close_cache(filepath, file)
                        jfiles.add(f.filename)
                end
                return jfiles
        end
 
+       # Cache a file as `{filepath}.tmp` and replace the original if different
+       private fun cache_file(filepath: String): FileWriter do
+               if toolcontext.opt_ant.value and filepath.file_exists then
+                       return new FileWriter.open("{filepath}.tmp")
+               else
+                       return new FileWriter.open(filepath)
+               end
+       end
+
+       # Close the writer and move tmp file to original if modified
+       private fun close_cache(filepath: String, file: FileWriter) do
+               file.close
+               if "{filepath}.tmp".file_exists then
+                       sys.system("if ! diff {filepath}.tmp {filepath} > /dev/null; then mv {filepath}.tmp {filepath}; else rm {filepath}.tmp; fi")
+               end
+       end
+
        # Compile Java generated files using `make`
        fun build_with_make(compiler: JavaCompiler, jfiles: Array[String]) do
                write_manifest(compiler)
@@ -172,18 +190,18 @@ redef class ModelBuilder
                antfile.write("<project>")
                antfile.write(" <target name=\"compile\">")
                antfile.write("  <mkdir dir=\"classes\"/>")
-        antfile.write("  <javac includes=\"{compiler.mainmodule.jname}_Main.java {jfiles.join(" ")}\" srcdir=\".\" destdir=\"classes\"/>")
+               antfile.write("  <javac includes=\"{compiler.mainmodule.jname}_Main.java {jfiles.join(" ")}\" srcdir=\".\" destdir=\"classes\"/>")
                antfile.write(" </target>")
                antfile.write(" <target name=\"jar\" depends=\"compile\">")
                antfile.write("  <jar destfile=\"{outpath}.jar\" basedir=\"classes\">")
                antfile.write("   <manifest>")
-        antfile.write("    <attribute name=\"Main-Class\" value=\"{jname}_Main\"/>")
+               antfile.write("    <attribute name=\"Main-Class\" value=\"{jname}_Main\"/>")
                antfile.write("   </manifest>")
                antfile.write("  </jar>")
                antfile.write(" </target>")
                antfile.write("</project>")
                antfile.close
-               self.toolcontext.info("Generated antfile: {antname}", 2)
+               toolcontext.info("Generated antfile: {antname}", 2)
        end
 
        # Write the Java manifest file