chore(doc-gen): trim leading blank lines from markdown content

Harp 0.17 does not allow blank lines to appear between filters and their
content. This change ensures that any blank lines that could appear have
been trimmed inside Nunkjucks.

Closes #3325

docs/angular.io-package/index.js

@@ -54,4 +54,11 @@ module.exports = new Package('angular.io', [basePackage])
 
 .config(function(getLinkInfo) {
   getLinkInfo.relativeLinks = true;
-});
+})
+
+
+.config(function(templateEngine, getInjectables) {
+  templateEngine.filters = templateEngine.filters.concat(getInjectables([require('./rendering/trimBlankLines')]));
+});
+
+

docs/angular.io-package/rendering/trimBlankLines.js

@@ -0,0 +1,12 @@
+module.exports = function(encodeCodeBlock) {
+  return {
+    name: 'trimBlankLines',
+    process: function(str) {
+      var lines = str.split(/\r?\n/);
+      while(lines[0] === '') {
+        lines.shift();
+      }
+      return lines.join('\n');
+    }
+  };
+};

docs/angular.io-package/templates/class.template.html

@@ -8,7 +8,7 @@ p.location-badge.
   defined in {$ githubViewLink(doc) $}
 
 :markdown
-{$ doc.description | indent(2, true) $}
+{$ doc.description | indent(2, true) | trimBlankLines $}
 
 {%- if doc.decorators %}
 .l-main-section
@@ -37,7 +37,7 @@ p.location-badge.
         {$ doc.constructorDoc.name $}{$ paramList(doc.constructorDoc.parameters) | indent(4, true) | trim $}
     {% endif %}
     :markdown
-{$ doc.constructorDoc.description | indent(6, true) | replace('## Example', '') | replace('# Example', '') $}
+{$ doc.constructorDoc.description | indent(6, true) | replace('## Example', '') | replace('# Example', '') | trimBlankLines $}
 
 
 {% endif -%}
@@ -52,8 +52,7 @@ p.location-badge.
         {$ member.name $}{$ paramList(member.parameters) | indent(4, true) | trim $}{$ returnType(doc.returnType) $}
     {% endif %}
     :markdown
-
-{$ member.description | indent(6, true) | replace('## Example', '') | replace('# Example', '')  $}
+{$ member.description | indent(6, true) | replace('## Example', '') | replace('# Example', '') | trimBlankLines $}
 
 
 

docs/angular.io-package/templates/function.template.html

@@ -17,6 +17,6 @@
     defined in {$ githubViewLink(doc) $}
 
   :markdown
-{$ doc.description | indent(4, true) $}
+{$ doc.description | indent(4, true) | trimBlankLines $}
 
 {% endblock %}

docs/angular.io-package/templates/var.template.html

@@ -9,5 +9,5 @@
     defined in {$ githubViewLink(doc) $}
 
   :markdown
-{$ doc.description | indent(4, true) $}
+{$ doc.description | indent(4, true) | trimBlankLines $}
 {% endblock %}