From c1c32688a4afc43f6addb99b8b5fa878944a70e3 Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Mon, 14 Jan 2019 15:42:48 -0800
Subject: Overhaul in progress, mostly working. Moved all the nomsu packages
 into lib/, including core/*. Changes to how nomsu environments and importing
 work.

---
 lib/core/errors.nom | 131 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 lib/core/errors.nom

(limited to 'lib/core/errors.nom')

diff --git a/lib/core/errors.nom b/lib/core/errors.nom
new file mode 100644
index 0000000..c878bb7
--- /dev/null
+++ b/lib/core/errors.nom
@@ -0,0 +1,131 @@
+#!/usr/bin/env nomsu -V6.14
+#
+    This file contains basic error reporting code
+    
+use "core/metaprogramming"
+use "core/operators"
+use "core/control_flow"
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+(fail $msg) compiles to "error(\(($msg as lua expr) if $msg else "nil"), 0);"
+(assume $condition) compiles to:
+    lua> ("
+        local \$assumption = 'Assumption failed: '..tostring((\$condition):get_source_code())
+    ")
+    
+    return
+        Lua ("
+            if not \($condition as lua expr) then
+                error(\(quote "\$assumption"), 0)
+            end
+        ")
+
+(assume $a == $b) compiles to:
+    lua> "local \$assumption = 'Assumption failed: '..tostring(\(\($a == $b) as nomsu))"
+    
+    define mangler
+    
+    return
+        Lua ("
+            do
+                local \(mangle "a"), \(mangle "b") = \($a as lua expr), \($b as lua expr)
+                if \(mangle "a") ~= \(mangle "b") then
+                    error(\(quote "\$assumption").."\\n"..tostring(\(mangle "a")).." != "..tostring(\
+            ..\(mangle "b")), 0)
+                end
+            end
+        ")
+
+test:
+    try: fail
+    $worked = (no)
+    try:
+        fail "xx"
+    ..if it fails with $failure:
+        $worked = (yes)
+    ..if it succeeds:
+        fail "'try' incorrectly ran success case."
+    assume $failure == "xx"
+    unless $worked:
+        fail "'try' failed to recover from failure"
+
+# Try/except
+[
+    try $action if it succeeds $success if it fails with $msg $fallback
+    try $action if it fails with $msg $fallback if it succeeds $success
+] all compile to:
+    $success_lua = ($success as lua)
+    if ((#"\$success_lua") > 0):
+        $success_lua, add "\n"
+    $success_lua, prepend "-- Success:\n"
+    $success_lua, 
+        add "if not _fell_through then return table.unpack(_result, 2) end"
+    $fallback_lua = ($fallback as lua)
+    if ((#"\$fallback_lua") > 0):
+        $msg_lua = ($msg as lua expr)
+        if ((#"\$msg_lua") > 0):
+            $fallback_lua, prepend "\n\$msg_lua = _result[2]\n"
+            if ($msg_lua, text, is lua id):
+                $fallback_lua, add free vars [($msg_lua, text)]
+    $fallback_lua, prepend "-- Failure:"
+    return
+        Lua ("
+            do
+                local _fell_through = false
+                local _result = {pcall(function()
+                    \($action as lua)
+                    _fell_through = true
+                end)}
+                if _result[1] then
+                    \$success_lua
+                else
+                    \$fallback_lua
+                end
+            end
+        ")
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+(try $action) parses as
+    try $action if it succeeds (do nothing) if it fails (do nothing)
+
+(try $action if it fails $fallback) parses as
+    try $action if it succeeds (do nothing) if it fails $fallback
+
+(try $action if it fails with $msg $fallback) parses as
+    try $action if it succeeds (do nothing) if it fails with $msg $fallback
+
+(try $action if it succeeds $success) parses as
+    try $action if it succeeds $success if it fails (do nothing)
+
+(try $action if it fails $fallback if it succeeds $success) parses as
+    try $action if it fails with (=lua "") $fallback if it succeeds $success
+
+(try $action if it succeeds $success if it fails $fallback) parses as
+    try $action if it succeeds $success if it fails with (=lua "") $fallback
+
+test:
+    $success = (no)
+    try:
+        do: fail
+        ..then always:
+            $success = (yes)
+    ..if it succeeds:
+        fail "'try ... then always ...' didn't propagate failure"
+    
+    unless $success:
+        fail "'try ... then always ...' didn't execute the 'always' code"
+
+(do $action then always $final_action) compiles to ("
+    do -- do/then always
+        local _fell_through = false
+        local _results = {pcall(function()
+            \($action as lua)
+            _fell_through = true
+        end)}
+        \($final_action as lua)
+        if not _results[1] then error(_results[2], 0) end
+        if not _fell_through then return table.unpack(_results, 2) end
+    end
+")
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