LACE: More error normalisation, and error rendering capability

5 files changed, 125 insertions, 15 deletions

diff --git a/lib/lace/builtin.lua b/lib/lace/builtin.lua
index 03fe7bc..e6c02f1 100644
--- a/lib/lace/builtin.lua
+++ b/lib/lace/builtin.lua
@@ -183,11 +183,7 @@ function builtin.define(compcontext, define, name, controltype, ...)
    local ctrltab, msg = controlfn(compcontext, controltype, ...)
    if type(ctrltab) ~= "table" then
       -- offset all the words in the error by 2 (for define and name)
-      if msg.words then
-	 for i = 1, #msg.words do
-	    msg.words[i] = msg.words[i] + 2
-	 end
-      end
+      msg = err.offset(msg, 2)
       return false, msg
    end
 
diff --git a/lib/lace/compiler.lua b/lib/lace/compiler.lua
index 4fd975b..1b0b21a 100644
--- a/lib/lace/compiler.lua
+++ b/lib/lace/compiler.lua
@@ -124,7 +124,7 @@ local function internal_compile_ruleset(compcontext, sourcename, content, suppre
    --   There's no unconditional result and no default, fake up a default and
    --     then use it.
    if not suppress_default and not uncond and not result then
-      return false, { msg = "No result set whatsoever", words = {} }
+      return err.error("No result set whatsoever")
    end
 
    if not suppress_default and not uncond then
diff --git a/lib/lace/engine.lua b/lib/lace/engine.lua
index dcf8a68..b4db68d 100644
--- a/lib/lace/engine.lua
+++ b/lib/lace/engine.lua
@@ -7,9 +7,7 @@
 -- For licence terms, see COPYING
 --
 
-local function _error(str, words)
-   return { msg = str, words = words }
-end
+local err = require 'lace.error'
 
 local function _dlace(ctx)
    local ret = ctx._lace or {}
@@ -21,7 +19,7 @@ local function set_define(exec_context, name, defn)
    local dlace = _dlace(exec_context)
    dlace.defs = dlace.defs or {}
    if dlace.defs[name] then
-      return false, _error("Attempted to redefine " .. name, {2})
+      return err.error("Attempted to redefine " .. name, {2})
    end
    dlace.defs[name] = defn
    return true
@@ -32,7 +30,7 @@ local function test_define(exec_context, name)
    dlace.defs = dlace.defs or {}
    local defn = dlace.defs[name]
    if not defn then
-      return nil, _error("Unknown definition: " .. name)
+      return err.error("Unknown definition: " .. name, {2}, true)
    end
    -- Otherwise we evaluate the definition and return it
    return defn.fn(exec_context, unpack(defn.args))
diff --git a/lib/lace/error.lua b/lib/lace/error.lua
index d52da1d..d71d21d 100644
--- a/lib/lace/error.lua
+++ b/lib/lace/error.lua
@@ -7,10 +7,67 @@
 -- For licence terms, see COPYING
 --
 
-local function _error(str, words)
-   return false, { msg = str, words = words or {} }
+local function _error(str, words, rnil)
+   local ret = false
+   if rnil then
+      ret = nil
+   end
+   return ret, { msg = str, words = words or {} }
+end
+
+local function _offset(err, offs)
+   if not err.words then
+      err.words = {}
+   end
+   for k, w in ipairs(err.words) do
+      err.words[k] = w + offs
+   end
+   return err
+end
+
+local function _augment(err, source, linenr)
+   err.source = source
+   err.linenr = linenr
+end
+
+local function _render(err)
+   -- A rendered error has four lines
+   -- The first line is the error message
+   local ret = { err.msg }
+   -- The second is the source filename and line
+   ret[2] = err.source.source .. " :: " .. tostring(err.linenr)
+   -- The third line is the line of the input
+   local srcline = err.source.lines[err.linenr] or {
+      original = "???", content = { {spos = 1, epos = 3, str = "???"} }
+   }
+   ret[3] = srcline.original
+   -- The fourth line is the highlight for each word in question
+   local wordset = {}
+   for _, word in ipairs(err.words) do
+      wordset[word] = true
+   end
+   local hlstr = ""
+   local cpos = 1
+   for w, info in ipairs(srcline.content) do
+      -- Ensure that we're up to the start position of the word
+      while (cpos < info.spos) do
+	 hlstr = hlstr .. " "
+	 cpos = cpos + 1
+      end
+      -- Highlight this word if appropriate
+      while (cpos <= info.epos) do
+	 hlstr = hlstr .. (wordset[w] and "^" or " ")
+	 cpos = cpos + 1
+      end
+   end
+   ret[4] = hlstr
+   -- The rendered error is those four strings joined by newlines
+   return table.concat(ret, "\n")
 end
 
 return {
-   error = _error
-}
\ No newline at end of file
+   error = _error,
+   offset = _offset,
+   augment = _augment,
+   render = _render,
+}
diff --git a/test/test-lace.error.lua b/test/test-lace.error.lua
index 4c15acd..471935b 100644
--- a/test/test-lace.error.lua
+++ b/test/test-lace.error.lua
@@ -38,6 +38,65 @@ function suite.error_formation()
    assert(ret2.words == words, "Words should be passed through")
 end
 
+function suite.error_offset()
+   local words = {3,5}
+   local f, err = error.error("msg", words)
+   local nerr = error.offset(err, 2)
+   assert(nerr == err, "Offset should return the same error it was given")
+   assert(words[1] == 5, "Offset should alter the first word")
+   assert(words[2] == 7, "Offset should alter all the words")
+end
+
+function suite.error_augmentation()
+   local f, err = error.error("msg")
+   local src = {}
+   error.augment(err, src, 10)
+   assert(err.source == src, "Augmented errors should contain their source data")
+   assert(err.linenr == 10, "Augmented errors should contain their error line")
+end
+
+function suite.error_render()
+   local f, err = error.error("msg", {1, 3})
+   local src = { source = "SOURCE", lines = {
+	 {
+	    original = "  ORIG LINE FISH",
+	    content = {
+	       { spos = 3, epos = 6, str = "ORIG" },
+	       { spos = 8, epos = 11, str = "LINE" },
+	       { spos = 13, epos = 16, str = "FISH" },
+	    }
+	 }
+      }
+   }
+   error.augment(err, src, 1)
+   local estr = error.render(err)
+   local line1, line2, line3, line4 = estr:match("^([^\n]*)\n([^\n]*)\n([^\n]*)\n([^\n]*)$")
+   assert(line1, "There is a line 1")
+   assert(line2, "There is a line 2")
+   assert(line3, "There is a line 3")
+   assert(line4, "There is a line 4")
+   assert(line1 == "msg", "The first line should be the error message")
+   assert(line2 == "SOURCE :: 1", "The second line is where the error happened")
+   assert(line3 == src.lines[1].original, "The third line is the original line")
+   assert(line4 == "  ^^^^      ^^^^", "The fourth line highlights relevant words")
+end
+
+function suite.error_render_bad_line()
+   local f, err = error.error("msg", {1, 3})
+   local src = { source = "SOURCE", lines = { } }
+   error.augment(err, src, 1)
+   local estr = error.render(err)
+   local line1, line2, line3, line4 = estr:match("^([^\n]*)\n([^\n]*)\n([^\n]*)\n([^\n]*)$")
+   assert(line1, "There is a line 1")
+   assert(line2, "There is a line 2")
+   assert(line3, "There is a line 3")
+   assert(line4, "There is a line 4")
+   assert(line1 == "msg", "The first line should be the error message")
+   assert(line2 == "SOURCE :: 1", "The second line is where the error happened")
+   assert(line3 == "???", "The third line is the original line")
+   assert(line4 == "^^^", "The fourth line highlights relevant words")
+end
+
 local count_ok = 0
 for _, testname in ipairs(testnames) do
 --   print("Run: " .. testname)