Support string interpolation for example names

spec/features/metadata_spec.cr

@@ -0,0 +1,9 @@
+require "../spec_helper"
+
+Spectator.describe "Spec metadata" do
+  let(interpolation) { "string interpolation" }
+
+  it "supports #{interpolation}" do |example|
+    expect(example.name).to eq("supports string interpolation")
+  end
+end

src/spectator/dsl/examples.cr

@@ -122,10 +122,12 @@ module Spectator::DSL
     # For anything else, it is stringified.
     # This is intended to be used to convert a description from the spec DSL to `Node#name`.
     private macro _spectator_example_name(what)
-      {% if what.is_a?(StringLiteral) ||
-              what.is_a?(StringInterpolation) ||
-              what.is_a?(NilLiteral) %}
+      {% if what.is_a?(StringLiteral) || what.is_a?(NilLiteral) %}
         {{what}}
+      {% elsif what.is_a?(StringInterpolation) %}
+        ->(example : ::Spectator::Example) do
+          example.with_context(\{{@type.name}}) { {{what}} }
+        end
       {% else %}
         {{what.stringify}}
       {% end %}

src/spectator/example.cr

@@ -28,11 +28,12 @@ module Spectator
     # Is pending if the example hasn't run.
     getter result : Result = PendingResult.new("Example not run")
 
+    @name_proc : Proc(Example, String)?
+
     # Creates the example.
     # An instance to run the test code in is given by *context*.
     # The *entrypoint* defines the test code (typically inside *context*).
     # The *name* describes the purpose of the example.
-    # It can be a `Symbol` to describe a type.
     # The *location* tracks where the example exists in source code.
     # The example will be assigned to *group* if it is provided.
     # A set of *metadata* can be used for filtering and modifying example behavior.
@@ -46,6 +47,24 @@ module Spectator
       group << self if group
     end
 
+    # Creates the example.
+    # An instance to run the test code in is given by *context*.
+    # The *entrypoint* defines the test code (typically inside *context*).
+    # The *name* describes the purpose of the example.
+    # It can be a proc to be evaluated in the context of the example.
+    # The *location* tracks where the example exists in source code.
+    # The example will be assigned to *group* if it is provided.
+    # A set of *metadata* can be used for filtering and modifying example behavior.
+    # Note: The metadata will not be merged with the parent metadata.
+    def initialize(@context : Context, @entrypoint : self ->,
+                   @name_proc : Example -> String, location : Location? = nil,
+                   @group : ExampleGroup? = nil, metadata = Metadata.new)
+      super(nil, location, metadata)
+
+      # Ensure group is linked.
+      group << self if group
+    end
+
     # Creates a dynamic example.
     # A block provided to this method will be called as-if it were the test code for the example.
     # The block will be given this example instance as an argument.
@@ -98,6 +117,10 @@ module Spectator
 
       begin
         @result = Harness.run do
+          if proc = @name_proc.as?(Proc(Example, String))
+            self.name = proc.call(self)
+          end
+
           @group.try(&.call_before_all)
           if (parent = @group)
             parent.call_around_each(procsy).call

src/spectator/example_builder.cr

@@ -8,6 +8,8 @@ module Spectator
   # Constructs examples.
   # Call `#build` to produce an `Example`.
   class ExampleBuilder < NodeBuilder
+    @name : Proc(Example, String) | String?
+
     # Creates the builder.
     # A proc provided by *context_builder* is used to create a unique `Context` for each example produced by `#build`.
     # The *entrypoint* indicates the proc used to invoke the test code in the example.
@@ -16,6 +18,15 @@ module Spectator
                    @name : String? = nil, @location : Location? = nil, @metadata : Metadata = Metadata.new)
     end
 
+    # Creates the builder.
+    # A proc provided by *context_builder* is used to create a unique `Context` for each example produced by `#build`.
+    # The *entrypoint* indicates the proc used to invoke the test code in the example.
+    # The *name* is an interpolated string that runs in the context of the example.
+    # *location*, and *metadata* will be applied to the `Example` produced by `#build`.
+    def initialize(@context_builder : -> Context, @entrypoint : Example ->,
+                   @name : Example -> String, @location : Location? = nil, @metadata : Metadata = Metadata.new)
+    end
+
     # Constructs an example with previously defined attributes and context.
     # The *parent* is an already constructed example group to nest the new example under.
     # It can be nil if the new example won't have a parent.