Add posix.readlink

Author: timfel

graalpython/com.oracle.graal.python.test/src/com/oracle/graal/python/test/module/PosixTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2018, Oracle and/or its affiliates.
+ * Copyright (c) 2017, 2019, Oracle and/or its affiliates.
  * Copyright (c) 2013, Regents of the University of California
  *
  * All rights reserved.
@@ -34,6 +34,7 @@
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.Paths;
 
 import org.junit.After;
 import org.junit.Before;
@@ -179,4 +180,16 @@ public void printToFile() throws IOException {
                         "print('hello', file=f)");
         assertEquals("hello\n", new String(Files.readAllBytes(tmpfile)));
     }
+
+    @Test
+    public void readlink() throws IOException {
+        Path symlinkPath = tmpfile.getParent().resolve(tmpfile.getFileName() + "__symlink");
+        try {
+            Path symlink = Files.createSymbolicLink(symlinkPath, Paths.get(tmpfile.toUri()));
+            assertPrints(tmpfile.toString() + "\n", "import posix\n" +
+                            "print(posix.readlink('" + symlink.toString() + "'))\n");
+        } finally {
+            Files.deleteIfExists(symlinkPath);
+        }
+    }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/PosixModuleBuiltins.java

@@ -1752,4 +1752,23 @@ protected GetTerminalSizeNode create() {
             return PosixModuleBuiltinsFactory.GetTerminalSizeNodeFactory.create();
         }
     }
+
+    @Builtin(name = "readlink", fixedNumOfPositionalArgs = 1, keywordArguments = {"dirFd"}, doc = "readlink(path, *, dir_fd=None) -> path\n" +
+                    "\nReturn a string representing the path to which the symbolic link points.\n")
+    @GenerateNodeFactory
+    abstract static class ReadlinkNode extends PythonBinaryBuiltinNode {
+        @Specialization
+        String readlinkPString(PString str, PNone none) {
+            return readlink(str.getValue(), none);
+        }
+
+        @Specialization
+        String readlink(String str, @SuppressWarnings("unused") PNone none) {
+            try {
+                return getContext().getEnv().getTruffleFile(str).getCanonicalFile().getPath();
+            } catch (IOException e) {
+                throw raise(OSError, e.getMessage());
+            }
+        }
+    }
 }