From 31023fba3c6d6e2d197d6802779cdc65d250e93e Mon Sep 17 00:00:00 2001
From: nebulon42 <nebulon42@mailbox.org>
Date: Sun, 2 Jul 2017 12:49:39 +0200
Subject: [PATCH] allow expressions in filters, fixes #377

---
 CHANGELOG.md                     | 2 ++
 docs/styling_concepts.rst        | 5 +++++
 lib/carto/parser.js              | 1 +
 test/rendering-mss/issue_377.mss | 3 +++
 test/rendering-mss/issue_377.xml | 6 ++++++
 5 files changed, 17 insertions(+)
 create mode 100644 test/rendering-mss/issue_377.mss
 create mode 100644 test/rendering-mss/issue_377.xml

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1ec0b65b0..2e3fe0c77 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,8 @@ There is a new command line / API switch (`-q / --quiet` / `quiet`) to suppress
 (`-o / --output` / `outputFormat`) to choose the output format. Possible values are `mapnik` (default)
 for Mapnik XML and `json` for the JSON variant (part of [#413](https://github.com/mapbox/carto/issues/413)).
 For Mapnik XML all character data as tag content is now prefixed with CDATA.
+* Expressions are allowed in filters e.g. `[height] % 50 = 0` or `[height] + 10 = 0`, fields have to be properly written within brackets
+([#377](https://github.com/mapbox/carto/issues/377))
 
 ### Breaking changes
 
diff --git a/docs/styling_concepts.rst b/docs/styling_concepts.rst
index 8aa5a9195..1184665da 100644
--- a/docs/styling_concepts.rst
+++ b/docs/styling_concepts.rst
@@ -134,3 +134,8 @@ String comparisons::
 
     /* a regular expression over name */
     #world[name =~ "A.*"]
+
+More complex expressions::
+
+    #world[[population] % 50 = 0]
+    #world[[population] * 2 < 1000]
diff --git a/lib/carto/parser.js b/lib/carto/parser.js
index 22b4d9624..5de8b861b 100644
--- a/lib/carto/parser.js
+++ b/lib/carto/parser.js
@@ -547,6 +547,7 @@ carto.Parser = function Parser(env) {
                 /*eslint-disable no-cond-assign */
                 if (key = $(/^[a-zA-Z0-9\-_]+/) ||
                     $(this.entities.quoted) ||
+                    $(this.expression) ||
                     $(this.entities.variable) ||
                     $(this.entities.keyword) ||
                     $(this.entities.field)) {
diff --git a/test/rendering-mss/issue_377.mss b/test/rendering-mss/issue_377.mss
new file mode 100644
index 000000000..0e0e750e7
--- /dev/null
+++ b/test/rendering-mss/issue_377.mss
@@ -0,0 +1,3 @@
+[[height] % 50 = 0] {
+    marker-fill: red;
+}
diff --git a/test/rendering-mss/issue_377.xml b/test/rendering-mss/issue_377.xml
new file mode 100644
index 000000000..bd992d1c1
--- /dev/null
+++ b/test/rendering-mss/issue_377.xml
@@ -0,0 +1,6 @@
+<Style filter-mode="first" name="style">
+  <Rule>
+    <Filter><![CDATA[([height]%50 = 0)]]></Filter>
+    <MarkersSymbolizer fill="#ff0000" />
+  </Rule>
+</Style>