Make IO Context available inside <script> (#27)

* Make IO Context properties available inside proxied IO

* Update NEWS.md

* move tests into ## Regression tests

NEWS.md

@@ -1,5 +1,9 @@
 # Release Notes
 
+## v0.9.4
+
+- Pull #27: Make IO Context available inside `<script>`
+
 ## v0.9.3
 
 - Pull #18: Interpolating within a paired tags

docs/src/attribute.md

@@ -125,7 +125,7 @@ desirable for use inside an attribute value.
     struct Custom data::String end
 
     @htl "<tag att=$(Custom("A&B"))/>"
-    #-> <tag att='…Custom(&quot;A&amp;B&quot;)'/>
+    #-> <tag att='Custom(&quot;A&amp;B&quot;)'/>
 
 This can be sometimes addressed by implementing `Base.print()`.
 

docs/src/primitives.md

@@ -10,11 +10,12 @@ it. There are several wrappers which drive special proxy handling.
 
 This utility class acts wraps an `IO` stream to provide HTML escaping.
 
-    io = IOBuffer()
+    io_buffer = IOBuffer()
+    io = IOContext(io_buffer, :hello => "world")
     ep = EscapeProxy(io)
 
     macro echo(expr)
-        :($expr; print(String(take!(io))))
+        :($expr; print(String(take!(io_buffer))))
     end
 
 The result of this proxy is that regular content printed to it is passed
@@ -24,6 +25,11 @@ along to the wrapped `IO`, after escaping the ampersand (`&`), less-than
     @echo print(ep, "(&'<\")")
     #-> (&amp;&apos;&lt;&quot;)
 
+Any [IO context properties](https://docs.julialang.org/en/v1/base/io-network/#Base.IOContext-Tuple{IO,%20Pair}) will be reflected by the `EscapeProxy`:
+
+    @echo print(ep, get(ep, :hello, "oops"))
+    #-> world
+
 ## Bypass
 
 This wrapper simply prints its content.

docs/src/script.md

@@ -167,3 +167,21 @@ It's important to handle unicode content properly.
 
     @htl("<script>alert($(s))</script>")
     #-> <script>alert("α\n")</script>
+
+## Regression tests
+
+Any [IO context properties](https://docs.julialang.org/en/v1/base/io-network/#Base.IOContext-Tuple{IO,%20Pair}) of the renderer can be used, as expected:
+
+    struct Hello end
+
+    function Base.show(io::IO, ::MIME"text/javascript", ::Hello)
+        print(io, get(io, :hello, "oops"))
+    end
+
+    h = @htl("""<script>const x = $(Hello())</script>""")
+
+    repr(
+        MIME"text/html"(), h; 
+        context=(:hello => "world")
+    )
+    #-> "<script>const x = world</script>"

src/primitives.jl

@@ -27,6 +27,8 @@ end
 
 Base.print(io::IO, x::Bypass) = print(io, x.content)
 
+abstract type IOProxy <: IO end
+
 """
     EscapeProxy(io) - wrap an `io` to perform HTML escaping
 
@@ -44,7 +46,7 @@ julia> print(ep, Bypass("<tag/>"))
 <tag/>
 ```
 """
-struct EscapeProxy{T<:IO} <: IO
+struct EscapeProxy{T<:IO} <: IOProxy
     io::T
 end
 
@@ -108,3 +110,11 @@ function Base.unsafe_write(ep::EscapeProxy, input::Ptr{UInt8}, nbytes::UInt)
     end
     return written
 end
+
+# IO passthrough methods:
+Base.in(key_value::Pair, io::IOProxy) = in(key_value, io.io)
+Base.haskey(io::IOProxy, key) = haskey(io.io, key)
+Base.getindex(io::IOProxy, key) = getindex(io.io, key)
+Base.get(io::IOProxy, key, default) = get(io.io, key, default)
+Base.keys(io::IOProxy) = keys(io.io)
+Base.displaysize(io::IOProxy) = displaysize(io.io)

src/script.jl

@@ -13,7 +13,7 @@ julia> print(gp, "</script>")
 ERROR: "Content within a script tag must not contain `</script>`"
 ```
 """
-mutable struct ScriptTagProxy{T<:IO} <: IO where {T}
+mutable struct ScriptTagProxy{T<:IO} <: IOProxy where {T}
     io::T
     index::Int
 

src/style.jl

@@ -13,7 +13,7 @@ julia> print(gp, "</style>")
 ERROR: "Content within a style tag must not contain `</style>`"
 ```
 """
-mutable struct StyleTagProxy{T<:IO} <: IO where {T}
+mutable struct StyleTagProxy{T<:IO} <: IOProxy where {T}
     io::T
     index::Int