Update path reading APIs to use optional values instead of erroring

5 files changed, 57 insertions, 33 deletions

diff --git a/docs/paths.md b/docs/paths.md
index 6408cc8a..a4437c6f 100644
--- a/docs/paths.md
+++ b/docs/paths.md
@@ -119,11 +119,12 @@ The base name of the file or directory.
 ### `by_line`
 
 **Description:**  
-Returns an iterator that can be used to iterate over a file one line at a time.
+Returns an iterator that can be used to iterate over a file one line at a time,
+or returns a null value if the file could not be opened.
 
 **Usage:**  
 ```markdown
-by_line(path: Path) -> func()->Text?
+by_line(path: Path) -> (func()->Text?)?
 ```
 
 **Parameters:**
@@ -131,11 +132,20 @@ by_line(path: Path) -> func()->Text?
 - `path`: The path of the file.
 
 **Returns:**  
-An iterator that can be used to get lines from a file one at a time.
+An iterator that can be used to get lines from a file one at a time or a null
+value if the file couldn't be read.
 
 **Example:**  
 ```markdown
-for line in (/dev/stdin):by_line():
+# Safely handle file not being readable:
+if lines := (./file.txt):by_line():
+    for line in lines:
+        say(line:upper())
+else:
+    say("Couldn't read file!")
+
+# Assume the file is readable and error if that's not the case:
+for line in (/dev/stdin):by_line()!:
     say(line:upper())
 ```
 
@@ -414,11 +424,12 @@ The path of the parent directory.
 ### `read`
 
 **Description:**  
-Reads the contents of the file at the specified path.
+Reads the contents of the file at the specified path or a null value if the
+file could not be read.
 
 **Usage:**  
 ```markdown
-read(path: Path) -> Text
+read(path: Path) -> Text?
 ```
 
 **Parameters:**
@@ -426,22 +437,29 @@ read(path: Path) -> Text
 - `path`: The path of the file to read.
 
 **Returns:**  
-The contents of the file. If the file does not exist, an error will be raised.
+The contents of the file. If the file could not be read, a null value will be
+returned. If the file can be read, but is not valid UTF8 data, an error will be
+raised.
 
 **Example:**  
 ```markdown
-content := (./file.txt):read()
+>> (./hello.txt):read()
+= "Hello"?
+
+>> (./nosuchfile.xxx):read()
+= !Text
 ```
 ---
 
 ### `read_bytes`
 
 **Description:**  
-Reads the contents of the file at the specified path.
+Reads the contents of the file at the specified path or a null value if the
+file could not be read.
 
 **Usage:**  
 ```markdown
-read_bytes(path: Path) -> [Byte]
+read_bytes(path: Path) -> [Byte]?
 ```
 
 **Parameters:**
@@ -449,11 +467,16 @@ read_bytes(path: Path) -> [Byte]
 - `path`: The path of the file to read.
 
 **Returns:**  
-The byte contents of the file. If the file does not exist, an error will be raised.
+The byte contents of the file. If the file cannot be read, a null value will be
+returned.
 
 **Example:**  
 ```markdown
-content := (./file.txt):read_bytes()
+>> (./hello.txt):read()
+= [72[B], 101[B], 108[B], 108[B], 111[B]]?
+
+>> (./nosuchfile.xxx):read()
+= ![Byte]
 ```
 
 ---
diff --git a/environment.c b/environment.c
index e0781468..6810f37a 100644
--- a/environment.c
+++ b/environment.c
@@ -262,7 +262,7 @@ env_t *new_compilation_unit(CORD *libname)
             {"append", "Path$append", "func(path:Path, text:Text, permissions=0o644[32])"},
             {"append_bytes", "Path$append_bytes", "func(path:Path, bytes:[Byte], permissions=0o644[32])"},
             {"base_name", "Path$base_name", "func(path:Path)->Text"},
-            {"by_line", "Path$by_line", "func(path:Path)->func()->Text?"},
+            {"by_line", "Path$by_line", "func(path:Path)->(func()->Text?)?"},
             {"children", "Path$children", "func(path:Path, include_hidden=no)->[Path]"},
             {"create_directory", "Path$create_directory", "func(path:Path, permissions=0o644[32])"},
             {"escape_int", "Int$value_as_text", "func(i:Int)->Path"},
@@ -277,8 +277,8 @@ env_t *new_compilation_unit(CORD *libname)
             {"is_socket", "Path$is_socket", "func(path:Path, follow_symlinks=yes)->Bool"},
             {"is_symlink", "Path$is_symlink", "func(path:Path)->Bool"},
             {"parent", "Path$parent", "func(path:Path)->Path"},
-            {"read", "Path$read", "func(path:Path)->Text"},
-            {"read_bytes", "Path$read_bytes", "func(path:Path)->[Byte]"},
+            {"read", "Path$read", "func(path:Path)->Text?"},
+            {"read_bytes", "Path$read_bytes", "func(path:Path)->[Byte]?"},
             {"relative", "Path$relative", "func(path:Path, relative_to=(./))->Path"},
             {"remove", "Path$remove", "func(path:Path, ignore_missing=no)"},
             {"resolved", "Path$resolved", "func(path:Path, relative_to=(./))->Path"},
diff --git a/stdlib/optionals.h b/stdlib/optionals.h
index e37d5345..b67badc4 100644
--- a/stdlib/optionals.h
+++ b/stdlib/optionals.h
@@ -9,13 +9,17 @@
 #include "util.h"
 
 #define OptionalBool_t uint8_t
+#define OptionalArray_t Array_t
+#define OptionalTable_t Table_t
+#define OptionalText_t Text_t
+#define OptionalClosure_t Closure_t
 
 extern const OptionalBool_t NULL_BOOL;
-extern const Table_t NULL_TABLE;
-extern const Array_t NULL_ARRAY;
-extern const Int_t NULL_INT;
-extern const Closure_t NULL_CLOSURE;
-extern const Text_t NULL_TEXT;
+extern const OptionalTable_t NULL_TABLE;
+extern const OptionalArray_t NULL_ARRAY;
+extern const OptionalInt_t NULL_INT;
+extern const OptionalClosure_t NULL_CLOSURE;
+extern const OptionalText_t NULL_TEXT;
 
 PUREFUNC bool is_null(const void *obj, const TypeInfo *non_optional_type);
 Text_t Optional$as_text(const void *obj, bool colorize, const TypeInfo *type);
diff --git a/stdlib/paths.c b/stdlib/paths.c
index bebb9389..afdd5426 100644
--- a/stdlib/paths.c
+++ b/stdlib/paths.c
@@ -244,16 +244,16 @@ public void Path$append_bytes(Path_t path, Array_t bytes, int permissions)
     _write(path, bytes, O_WRONLY | O_APPEND | O_CREAT, permissions);
 }
 
-public Array_t Path$read_bytes(Path_t path)
+public OptionalArray_t Path$read_bytes(Path_t path)
 {
     path = Path$_expand_home(path);
     int fd = open(Text$as_c_string(path), O_RDONLY);
     if (fd == -1)
-        fail("Could not read file: %k (%s)", &path, strerror(errno));
+        return NULL_ARRAY;
 
     struct stat sb;
     if (fstat(fd, &sb) != 0)
-        fail("Could not read file: %k (%s)", &path, strerror(errno));
+        return NULL_ARRAY;
 
     if ((sb.st_mode & S_IFMT) == S_IFREG) { // Use memory mapping if it's a real file:
         const char *mem = mmap(NULL, (size_t)sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
@@ -269,7 +269,7 @@ public Array_t Path$read_bytes(Path_t path)
             char chunk[256];
             ssize_t just_read = read(fd, chunk, sizeof(chunk));
             if (just_read < 0)
-                fail("Failed while reading file: %k (%s)", &path, strerror(errno));
+                return NULL_ARRAY;
             else if (just_read == 0) {
                 if (errno == EAGAIN || errno == EINTR)
                     continue;
@@ -287,17 +287,14 @@ public Array_t Path$read_bytes(Path_t path)
                 break;
         }
         close(fd);
-
-        if (u8_check((uint8_t*)content, len) != NULL)
-            fail("File does not contain valid UTF8 data!");
-
         return (Array_t){.data=content, .atomic=1, .stride=1, .length=len};
     }
 }
 
-public Text_t Path$read(Path_t path)
+public OptionalText_t Path$read(Path_t path)
 {
     Array_t bytes = Path$read_bytes(path);
+    if (bytes.length < 0) return NULL_TEXT;
     return Text$from_bytes(bytes);
 }
 
@@ -480,13 +477,13 @@ static Text_t _next_line(FILE **f)
     return line_text;
 }
 
-public Closure_t Path$by_line(Path_t path)
+public OptionalClosure_t Path$by_line(Path_t path)
 {
     path = Path$_expand_home(path);
 
     FILE *f = fopen(Text$as_c_string(path), "r");
     if (f == NULL)
-        fail("Could not read file: %k (%s)", &path, strerror(errno));
+        return NULL_CLOSURE;
 
     FILE **wrapper = GC_MALLOC(sizeof(FILE*));
     *wrapper = f;
diff --git a/stdlib/paths.h b/stdlib/paths.h
index d06d4fdc..65d98a0c 100644
--- a/stdlib/paths.h
+++ b/stdlib/paths.h
@@ -29,8 +29,8 @@ void Path$write(Path_t path, Text_t text, int permissions);
 void Path$write_bytes(Path_t path, Array_t bytes, int permissions);
 void Path$append(Path_t path, Text_t text, int permissions);
 void Path$append_bytes(Path_t path, Array_t bytes, int permissions);
-Text_t Path$read(Path_t path);
-Array_t Path$read_bytes(Path_t path);
+OptionalText_t Path$read(Path_t path);
+OptionalArray_t Path$read_bytes(Path_t path);
 void Path$remove(Path_t path, bool ignore_missing);
 void Path$create_directory(Path_t path, int permissions);
 Array_t Path$children(Path_t path, bool include_hidden);