stdlib: Make io failures recoverable by returning a result

src/comp/driver/rustc.rs

@@ -11,7 +11,7 @@ import syntax::print::{pp, pprust};
 import util::{ppaux, common, filesearch};
 import back::link;
 import lib::llvm;
-import std::{fs, option, str, vec, int, io, run, getopts};
+import std::{fs, option, str, vec, int, io, run, getopts, result};
 import std::map::mk_hashmap;
 import std::option::{some, none};
 import std::getopts::{optopt, optmulti, optflag, optflagopt, opt_present};
@@ -77,10 +77,16 @@ fn parse_input(sess: session::session, cfg: ast::crate_cfg, input: str) ->
 
 fn parse_input_src(sess: session::session, cfg: ast::crate_cfg, infile: str)
    -> {crate: @ast::crate, src: str} {
-    let srcbytes =
-        if infile != "-" {
-            io::file_reader(infile)
-        } else { io::stdin() }.read_whole_stream();
+    let srcbytes = if infile != "-" {
+        alt io::file_reader(infile) {
+          result::ok(reader) { reader }
+          result::err(e) {
+            sess.fatal(e)
+          }
+        }
+    } else {
+        io::stdin()
+    }.read_whole_stream();
     let src = str::unsafe_from_bytes(srcbytes);
     let crate =
         parser::parse_crate_from_source_str(infile, src, cfg,

src/comp/syntax/codemap.rs

@@ -1,4 +1,4 @@
-import std::{vec, uint, str, term, io, option};
+import std::{vec, uint, str, term, io, option, result};
 import std::option::{some, none};
 
 type filename = str;
@@ -154,7 +154,13 @@ fn maybe_highlight_lines(sp: option::t<span>, cm: codemap,
 
         // FIXME: reading in the entire file is the worst possible way to
         //        get access to the necessary lines.
-        let file = io::read_whole_file_str(lines.name);
+        let file = alt io::read_whole_file_str(lines.name) {
+          result::ok(file) { file }
+          result::err(e) {
+            emit_error(none, e, cm);
+            fail;
+          }
+        };
         let fm = get_filemap(cm, lines.name);
 
         // arbitrarily only print up to six lines of the error

src/comp/syntax/parse/parser.rs

@@ -1,5 +1,5 @@
 
-import std::{io, vec, str, option, either};
+import std::{io, vec, str, option, either, result};
 import std::option::{some, none};
 import std::either::{left, right};
 import std::map::{hashmap, new_str_hash};
@@ -53,7 +53,16 @@ type parser =
 fn new_parser_from_file(sess: parse_sess, cfg: ast::crate_cfg, path: str,
                         chpos: uint, byte_pos: uint, ftype: file_type) ->
    parser {
-    let src = io::read_whole_file_str(path);
+    let src = alt io::read_whole_file_str(path) {
+      result::ok(src) {
+        // FIXME: This copy is unfortunate
+        src
+      }
+      result::err(e) {
+        codemap::emit_error(none, e, sess.cm);
+        fail;
+      }
+    };
     let filemap = codemap::new_filemap(path, chpos, byte_pos);
     sess.cm.files += [filemap];
     let itr = @interner::mk(str::hash, str::eq);

src/compiletest/header.rs

@@ -63,7 +63,7 @@ fn is_test_ignored(config: config, testfile: str) -> bool {
 }
 
 fn iter_header(testfile: str, it: block(str)) {
-    let rdr = io::file_reader(testfile);
+    let rdr = std::result::get(io::file_reader(testfile));
     while !rdr.eof() {
         let ln = rdr.read_line();
 

src/compiletest/runtest.rs

@@ -5,6 +5,7 @@ import std::fs;
 import std::os;
 import std::vec;
 import std::test;
+import std::result;
 
 import common::mode_run_pass;
 import common::mode_run_fail;
@@ -92,7 +93,7 @@ fn run_pretty_test(cx: cx, props: test_props, testfile: str) {
     let rounds =
         alt props.pp_exact { option::some(_) { 1 } option::none. { 2 } };
 
-    let srcs = [io::read_whole_file_str(testfile)];
+    let srcs = [result::get(io::read_whole_file_str(testfile))];
 
     let round = 0;
     while round < rounds {
@@ -112,7 +113,7 @@ fn run_pretty_test(cx: cx, props: test_props, testfile: str) {
         alt props.pp_exact {
           option::some(file) {
             let filepath = fs::connect(fs::dirname(testfile), file);
-            io::read_whole_file_str(filepath)
+            result::get(io::read_whole_file_str(filepath))
           }
           option::none. { srcs[vec::len(srcs) - 2u] }
         };
@@ -339,7 +340,8 @@ fn dump_output(config: config, testfile: str, out: str, err: str) {
 #[cfg(target_os = "linux")]
 fn dump_output_file(config: config, testfile: str, out: str, extension: str) {
     let outfile = make_out_name(config, testfile, extension);
-    let writer = io::file_writer(outfile, [io::create, io::truncate]);
+    let writer = result::get(
+        io::file_writer(outfile, [io::create, io::truncate]));
     writer.write_str(out);
 }
 

src/fuzzer/fuzzer.rs

@@ -1,7 +1,7 @@
 use std;
 use rustc;
 
-import std::{fs, io, getopts, math, vec, str, int, uint, option};
+import std::{fs, io, getopts, math, vec, str, int, uint, option, result};
 import std::getopts::{optopt, opt_present, opt_str};
 import std::io::stdout;
 
@@ -13,7 +13,9 @@ tag test_mode { tm_converge; tm_run; }
 type context = { mode: test_mode }; // + rng
 
 fn write_file(filename: str, content: str) {
-    io::file_writer(filename, [io::create, io::truncate]).write_str(content);
+    result::get(
+        io::file_writer(filename, [io::create, io::truncate]))
+        .write_str(content);
     // Work around https://github.com/graydon/rust/issues/726
     std::run::run_program("chmod", ["644", filename]);
 }
@@ -517,7 +519,7 @@ fn check_convergence(files: [str]) {
     log_err #fmt["pp convergence tests: %u files", vec::len(files)];
     for file in files {
         if !file_might_not_converge(file) {
-            let s = io::read_whole_file_str(file);
+            let s = result::get(io::read_whole_file_str(file));
             if !content_might_not_converge(s) {
                 log_err #fmt["pp converge: %s", file];
                 // Change from 7u to 2u once https://github.com/graydon/rust/issues/850 is fixed
@@ -533,7 +535,7 @@ fn check_variants(files: [str], cx: context) {
             cont;
         }
 
-        let s = io::read_whole_file_str(file);
+        let s = result::get(io::read_whole_file_str(file));
         if contains(s, "#") {
             cont; // Macros are confusing
         }

src/lib/io.rs

@@ -173,14 +173,16 @@ fn stdin() -> reader {
     ret new_reader(FILE_buf_reader(rustrt::rust_get_stdin(), option::none));
 }
 
-fn file_reader(path: str) -> reader {
+fn file_reader(path: str) -> result::t<reader, str> {
     let f = str::as_buf(path, {|pathbuf|
         str::as_buf("r", {|modebuf|
             os::libc::fopen(pathbuf, modebuf)
         })
     });
-    if f as uint == 0u { log_err "error opening " + path; fail; }
-    ret new_reader(FILE_buf_reader(f, option::some(@FILE_res(f))));
+    ret if f as uint == 0u { result::err("error opening " + path) }
+    else {
+        result::ok(new_reader(FILE_buf_reader(f, option::some(@FILE_res(f)))))
+    }
 }
 
 
@@ -278,7 +280,8 @@ obj fd_buf_writer(fd: int, res: option::t<@fd_res>) {
     }
 }
 
-fn file_buf_writer(path: str, flags: [fileflag]) -> buf_writer {
+fn file_buf_writer(path: str,
+                   flags: [fileflag]) -> result::t<buf_writer, str> {
     let fflags: int =
         os::libc_constants::O_WRONLY() | os::libc_constants::O_BINARY();
     for f: fileflag in flags {
@@ -296,12 +299,12 @@ fn file_buf_writer(path: str, flags: [fileflag]) -> buf_writer {
                                        os::libc_constants::S_IRUSR() |
                                            os::libc_constants::S_IWUSR())
                     });
-    if fd < 0 {
-        log_err "error opening file for writing";
+    ret if fd < 0 {
         log_err sys::last_os_error();
-        fail;
+        result::err("error opening " + path)
+    } else {
+        result::ok(fd_buf_writer(fd, option::some(@fd_res(fd))))
     }
-    ret fd_buf_writer(fd, option::some(@fd_res(fd)));
 }
 
 type writer =
@@ -359,13 +362,15 @@ obj new_writer(out: buf_writer) {
     }
 }
 
-fn file_writer(path: str, flags: [fileflag]) -> writer {
-    ret new_writer(file_buf_writer(path, flags));
+fn file_writer(path: str, flags: [fileflag]) -> result::t<writer, str> {
+    result::chain(file_buf_writer(path, flags), { |w|
+        result::ok(new_writer(w))
+    })
 }
 
 
 // FIXME: fileflags
-fn buffered_file_buf_writer(path: str) -> buf_writer {
+fn buffered_file_buf_writer(path: str) -> result::t<buf_writer, str> {
     let f =
         str::as_buf(path,
                     {|pathbuf|
@@ -374,8 +379,8 @@ fn buffered_file_buf_writer(path: str) -> buf_writer {
                                         os::libc::fopen(pathbuf, modebuf)
                                     })
                     });
-    if f as uint == 0u { log_err "error opening " + path; fail; }
-    ret FILE_writer(f, option::some(@FILE_res(f)));
+    ret if f as uint == 0u { result::err("error opening " + path) }
+    else { result::ok(FILE_writer(f, option::some(@FILE_res(f)))) }
 }
 
 
@@ -452,14 +457,18 @@ fn seek_in_buf(offset: int, pos: uint, len: uint, whence: seek_style) ->
     ret bpos as uint;
 }
 
-fn read_whole_file_str(file: str) -> str {
-    str::unsafe_from_bytes(read_whole_file(file))
+fn read_whole_file_str(file: str) -> result::t<str, str> {
+    result::chain(read_whole_file(file), { |bytes|
+        result::ok(str::unsafe_from_bytes(bytes))
+    })
 }
 
-fn read_whole_file(file: str) -> [u8] {
+fn read_whole_file(file: str) -> result::t<[u8], str> {
 
     // FIXME: There's a lot of copying here
-    file_reader(file).read_whole_stream()
+    result::chain(file_reader(file), { |rdr|
+        result::ok(rdr.read_whole_stream())
+    })
 }
 
 

src/lib/result.rs

@@ -41,6 +41,8 @@ fn get<T, U>(res: t<T, U>) -> T {
     alt res {
       ok(t) { t }
       err(_) {
+        // FIXME: Serialize the error value
+        // and include it in the fail message
         fail "get called on error result";
       }
     }

src/test/bench/task-perf-word-count.rs

@@ -20,6 +20,7 @@ import std::io;
 
 import std::time;
 import std::u64;
+import std::result;
 
 import std::task;
 import std::task::joinable_task;
@@ -30,7 +31,7 @@ import std::comm::recv;
 import std::comm::send;
 
 fn map(filename: str, emit: map_reduce::putter) {
-    let f = io::file_reader(filename);
+    let f = result::get(io::file_reader(filename));
 
 
     while true {

src/test/compile-fail/missingmod.rc

@@ -0,0 +1,3 @@
+// error-pattern:error opening
+
+mod doesnotexist;

src/test/stdtest/io.rs

@@ -2,6 +2,7 @@
 use std;
 import std::io;
 import std::str;
+import std::result;
 
 #[cfg(target_os = "linux")]
 #[cfg(target_os = "win32")]
@@ -13,10 +14,10 @@ fn test_simple() {
     log frood;
     {
         let out: io::writer =
-            io::file_writer(tmpfile, [io::create, io::truncate]);
+            result::get(io::file_writer(tmpfile, [io::create, io::truncate]));
         out.write_str(frood);
     }
-    let inp: io::reader = io::file_reader(tmpfile);
+    let inp: io::reader = result::get(io::file_reader(tmpfile));
     let frood2: str = inp.read_c_str();
     log frood2;
     assert (str::eq(frood, frood2));
@@ -28,3 +29,48 @@ fn test_simple() {
 #[ignore]
 fn test_simple() { }
 
+#[test]
+fn file_reader_not_exist() {
+    alt io::file_reader("not a file") {
+      result::err(e) {
+        assert e == "error opening not a file";
+      }
+      result::ok(_) { fail; }
+    }
+}
+
+#[cfg(target_os = "linux")]
+#[cfg(target_os = "win32")]
+#[test]
+fn file_buf_writer_bad_name() {
+    alt io::file_buf_writer("/?", []) {
+      result::err(e) {
+        assert e == "error opening /?";
+      }
+      result::ok(_) { fail; }
+    }
+}
+
+// FIXME (726)
+#[cfg(target_os = "macos")]
+#[test]
+#[ignore]
+fn file_buf_writer_bad_name() { }
+
+#[cfg(target_os = "linux")]
+#[cfg(target_os = "win32")]
+#[test]
+fn buffered_file_buf_writer_bad_name() {
+    alt io::buffered_file_buf_writer("/?") {
+      result::err(e) {
+        assert e == "error opening /?";
+      }
+      result::ok(_) { fail; }
+    }
+}
+
+// FIXME (726)
+#[cfg(target_os = "macos")]
+#[test]
+#[ignore]
+fn buffered_file_buf_writer_bad_name() { }