add lua filter for links to fix #43

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: sandpaper
 Title: Create and Curate Carpentries Lessons
-Version: 0.0.0.9033
+Version: 0.0.0.9034
 Authors@R: c(
     person(given = "Zhian N.",
            family = "Kamvar",

NEWS.md

@@ -1,3 +1,16 @@
+# sandpaper 0.0.0.9034
+
+NEW FEATURES
+------------
+
+ - Authors can now cross-link between files within the lesson as they appear in
+   the lesson instead of trying to guess how the link would appear on the
+   website. For example, if you wanted to reference `learners/setup.md` in 
+   `episodes/introduction.md`, you would write `[setup](../learners/setup.md)`
+   and it will be automatically converted to the correct URL in the website
+   (#43). This is still backwards compatible with the previous iteration of
+   writing the flattened link (as it would appear on the website).
+
 # sandpaper 0.0.0.9033
 
 NEW FEATURES

inst/rmarkdown/lua/lesson.lua

@@ -7,6 +7,7 @@ function Set (list)
   for _, l in ipairs(list) do set[l] = true end
   return set
 end
+
 local blocks = Set{
   "callout",
   "objectives",
@@ -272,7 +273,53 @@ handle_our_divs = function(el)
   return el
 end
 
+-- Flatten relative links for HTML output
+--
+-- 1. removes any leading ../[folder]/ from the links to prepare them for the
+--    way the resources appear in the HTML site
+-- 2. renames all local Rmd and md files to .html 
+--
+-- NOTE: it _IS_ possible to use variable expansion with this so that we can
+--       configure this to do specific things (e.g. decide how we want the
+--       architecture of the final site to be)
+-- function expand (s)
+--   s = s:gsub("$(%w+)", function(n)
+--      return _G[n] -- substitute with global variable
+--   end)
+--   return s
+-- end
+flatten_links = function(el)
+  local pat = "^%.%./"
+  local tgt;
+  if el.target == nil then
+    tgt = el.src
+  else
+    tgt = el.target
+  end
+  -- Flatten local redirects, e.ge. ../episodes/link.md goes to link.md
+  tgt,_ = tgt:gsub(pat.."episodes/", "")
+  tgt,_ = tgt:gsub(pat.."learners/", "")
+  tgt,_ = tgt:gsub(pat.."instructors/", "")
+  tgt,_ = tgt:gsub(pat.."profiles/", "")
+  tgt,_ = tgt:gsub(pat, "")
+  -- rename local markdown/Rmarkdown
+  -- link.md goes to link.html
+  -- link.md#section1 goes to link.html#section1
+  if text.sub(tgt, 1, 5) ~= "http"  then
+    tgt,_ = tgt:gsub("%.R?md(#[%S]+)$", ".html%1")
+    tgt,_ = tgt:gsub("%.R?md$", ".html")
+  end
+  if el.target == nil then
+    el.src = tgt;
+  else
+    el.target = tgt;
+  end
+  return el
+end
+
 return {
-  {Meta = get_timings},
-  {Div = handle_our_divs}
+  {Meta  = get_timings},
+  {Link  = flatten_links},
+  {Image = flatten_links},
+  {Div   = handle_our_divs}
 }

tests/testthat/_snaps/render_html.md

@@ -24,6 +24,9 @@
       ,Div ("",["challenge"],[])
        [Header 2 ("",[],[]) [Str "Challenge"]
        ,Para [Str "How",Space,Str "do",Space,Str "you",Space,Str "write",Space,Str "markdown",Space,Str "divs?"]
+       ,Para [Str "This",Space,Link ("",[],[]) [Str "link",Space,Str "should",Space,Str "be",Space,Str "transformed"] ("Setup.html","")]
+       ,Para [Str "This",Space,Link ("",[],[]) [Str "too"] ("Setup.html#windows-setup","windows setup")]
+       ,Para [Image ("",[],[("alt","alt text")]) [Str "link",Space,Str "should",Space,Str "be",Space,Str "transformed"] ("fig/Setup.png","fig:")]
        ,Div ("",["solution"],[])
         [Header 2 ("write-now",[],[]) [Str "Write",Space,Str "now"]
         ,Para [Str "just",Space,Str "write",Space,Str "it,",Space,Str "silly."]]]
@@ -96,6 +99,12 @@
       <div class="section level2">
       <h2>Challenge</h2>
       <p>How do you write markdown divs?</p>
+      <p>This <a href="Setup.html">link should be transformed</a></p>
+      <p>This <a href="Setup.html#windows-setup" title="windows setup">too</a></p>
+      <div class="figure">
+      <img src="fig/Setup.png" alt="alt text" alt="" />
+      <p class="caption">link should be transformed</p>
+      </div>
       </div>
       <div id="write-now" class="section level2 solution">
       <h2>Write now</h2>

tests/testthat/test-render_html.R

@@ -21,6 +21,12 @@ ex <- c("---",
   "", 
   "How do you write markdown divs?",
   "", 
+  "This [link should be transformed](../learners/Setup.md)",
+  "",
+  "This [too](../learners/Setup.md#windows-setup 'windows setup')",
+  "",
+  "![link should be transformed](../episodes/fig/Setup.png){alt='alt text'}",
+  "", 
   "::: solution",
   "",
   "# Write now",