Add 'unique' filter

CHANGELOG.md

@@ -1,3 +1,10 @@
+# 0.15.2
+
+### Enhancements
+
+- Added support for unique filter using `unique`. This filter allows you to extract unique values from an array
+  [David Bertet](https://github.com/DavidBertet)
+
 ## 0.15.1
 
 ### Bug Fixes

Sources/Stencil/Extension.swift

@@ -84,6 +84,7 @@ class DefaultExtension: Extension {
     registerFilter("split", filter: splitFilter)
     registerFilter("indent", filter: indentFilter)
     registerFilter("filter", filter: filterFilter)
+    registerFilter("unique", filter: unique)
   }
 }
 

Sources/Stencil/Filters.swift

@@ -137,3 +137,12 @@ func filterFilter(value: Any?, arguments: [Any?], context: Context) throws -> An
     try expr.resolve(context)
   }
 }
+
+func unique(_ value: Any?) -> Any? {
+  if let array = value as? [any Hashable] {
+    var seen: Set<String> = []
+    return array.filter { seen.insert(stringify($0)).inserted }
+  } else {
+    return value
+  }
+}

Tests/StencilTests/EnvironmentBaseAndChildTemplateSpec.swift

@@ -33,7 +33,7 @@ final class EnvironmentBaseAndChildTemplateTests: XCTestCase {
     baseTemplate = try environment.loadTemplate(name: "invalid-base.html")
 
     try expectError(
-      reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+      reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
       childToken: "extends \"invalid-base.html\"",
       baseToken: "target|unknown"
     )
@@ -67,7 +67,7 @@ final class EnvironmentBaseAndChildTemplateTests: XCTestCase {
     )
 
     try expectError(
-      reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+      reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
       childToken: "target|unknown",
       baseToken: nil
     )

Tests/StencilTests/EnvironmentIncludeTemplateSpec.swift

@@ -35,7 +35,7 @@ final class EnvironmentIncludeTemplateTests: XCTestCase {
     includedTemplate = try environment.loadTemplate(name: "invalid-include.html")
 
     try expectError(
-      reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+      reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
       token: #"include "invalid-include.html""#,
       includedToken: "target|unknown"
     )

Tests/StencilTests/EnvironmentSpec.swift

@@ -91,55 +91,55 @@ final class EnvironmentTests: XCTestCase {
     it("reports syntax error in for tag") {
       self.template = "{% for name in names|unknown %}{{ name }}{% endfor %}"
       try self.expectError(
-        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
         token: "names|unknown"
       )
     }
 
     it("reports syntax error in for-where tag") {
       self.template = "{% for name in names where name|unknown %}{{ name }}{% endfor %}"
       try self.expectError(
-        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
         token: "name|unknown"
       )
     }
 
     it("reports syntax error in if tag") {
       self.template = "{% if name|unknown %}{{ name }}{% endif %}"
       try self.expectError(
-        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
         token: "name|unknown"
       )
     }
 
     it("reports syntax error in elif tag") {
       self.template = "{% if name %}{{ name }}{% elif name|unknown %}{% endif %}"
       try self.expectError(
-        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
         token: "name|unknown"
       )
     }
 
     it("reports syntax error in ifnot tag") {
       self.template = "{% ifnot name|unknown %}{{ name }}{% endif %}"
       try self.expectError(
-        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
         token: "name|unknown"
       )
     }
 
     it("reports syntax error in filter tag") {
       self.template = "{% filter unknown %}Text{% endfilter %}"
       try self.expectError(
-        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
         token: "filter unknown"
       )
     }
 
     it("reports syntax error in variable tag") {
       self.template = "{{ name|unknown }}"
       try self.expectError(
-        reason: "Unknown filter 'unknown'. Found similar filters: 'uppercase'.",
+        reason: "Unknown filter 'unknown'. Found similar filters: 'unique'.",
         token: "name|unknown"
       )
     }

Tests/StencilTests/FilterSpec.swift

@@ -423,6 +423,26 @@ final class FilterTests: XCTestCase {
     }
   }
 
+  func testUniqueFilter() {
+    let template = Template(templateString: """
+      {{ value|unique }}
+      """)
+
+    it("collection of strings") {
+      let result = try template.render(Context(dictionary: ["value": ["One", "Two", "One", "two"]]))
+      try expect(result) == """
+      ["One", "Two", "two"]
+      """
+    }
+
+    it("mixed-type collection") {
+      let result = try template.render(Context(dictionary: ["value": ["One", 2, true, 2, true, 10.5, "2", "five", "One"]]))
+      try expect(result) == """
+      ["One", 2, true, 10.5, "five"]
+      """
+    }
+  }
+
   private func expectError(
     reason: String,
     token: String,

docs/builtins.rst

@@ -449,3 +449,14 @@ Applies the filter with the name provided as an argument to the current expressi
     {{ string|filter:myfilter }}
 
 This expression will resolve the `myfilter` variable, find a filter named the same as resolved value, and will apply it to the `string` variable. I.e. if `myfilter` variable resolves to string `uppercase` this expression will apply file `uppercase` to `string` variable.
+
+``unique``
+~~~~~~~~~
+
+Returns a list of unique items from the given value.
+
+.. code-block:: html+django
+
+    {{ value|unique }}
+
+The unique items are yielded in the same order as their first occurrence in the iterable passed to the filter.