Write to the generated README the actual list of products (#626)

Author: giordano

src/AutoBuild.jl

@@ -987,6 +987,7 @@ function build_jll_package(src_name::String, build_version::VersionNumber, code_
     mkpath(joinpath(code_dir, "src", "wrappers"))
 
     platforms = keys(build_output_meta)
+    products_info = Dict{Any,Any}
     for platform in platforms
         if verbose
             @info("Generating jll package for $(triplet(platform)) in $(code_dir)")
@@ -1223,44 +1224,63 @@ function build_jll_package(src_name::String, build_version::VersionNumber, code_
         """)
     end
 
+    product_names(p::ExecutableProduct) = p.binnames
+    product_names(p::FileProduct) = p.paths
+    product_names(p::LibraryProduct) = p.libnames
     # Add a README.md
     open(joinpath(code_dir, "README.md"), "w") do io
-        print(io, """
-        # $(src_name)_jll.jl
-
-        This is an autogenerated package constructed using [`BinaryBuilder.jl`](https://github.com/JuliaPackaging/BinaryBuilder.jl).
-
-        ## Usage
-
-        The code bindings within this package are autogenerated from the `Products` defined within the `build_tarballs.jl` file that generated this package.  For example purposes, we will assume that the following products were defined:
-
-        ```julia
-        products = [
-            FileProduct("src/data.txt", :data_txt),
-            LibraryProduct("libdataproc", :libdataproc),
-            ExecutableProduct("mungify", :mungify_exe)
-        ]
-        ```
-
-        With such products defined, this package will contain `data_txt`, `libdataproc` and `mungify_exe` symbols exported. For `FileProduct` variables, the exported value is a string pointing to the location of the file on-disk.  For `LibraryProduct` variables, it is a string corresponding to the `SONAME` of the desired library (it will have already been `dlopen()`'ed, so typical `ccall()` usage applies), and for `ExecutableProduct` variables, the exported value is a function that can be called to set appropriate environment variables.  Example:
-
-        ```julia
-        using $(src_name)_jll
-
-        # For file products, you can access its file location directly:
-        data_lines = open(data_txt, "r") do io
-            readlines(io)
-        end
-
-        # For library products, you can use the exported variable name in `ccall()` invocations directly
-        num_chars = ccall((libdataproc, :count_characters), Cint, (Cstring, Cint), data_lines[1], length(data_lines[1]))
-
-        # For executable products, you can use the exported variable name as a function that you can call
-        mungify_exe() do mungify_exe_path
-            run(`\$mungify_exe_path \$num_chars`)
-        end
-        ```
-        """)
+        print(io,
+              """
+              # $(src_name)_jll.jl
+
+              This is an autogenerated package constructed using [`BinaryBuilder.jl`](https://github.com/JuliaPackaging/BinaryBuilder.jl).
+
+              """,
+              iszero(length(keys(products_info))) ? "" :
+              """
+              ## Products
+
+              The code bindings within this package are autogenerated from the following `Products` defined within the `build_tarballs.jl` file that generated this package:
+
+              ```julia
+              products = [
+              $(join(collect("    $(typeof(p))($(product_names(p)), :$(variable_name(p)))" for (p, _) in products_info), ",\n"))
+              ]
+              ```
+
+              """,
+              """
+              ## Usage example
+
+              For example purposes, we will assume that the following products were defined in the imaginary package `Example_jll`:
+
+              ```julia
+              products = [
+                  FileProduct("src/data.txt", :data_txt),
+                  LibraryProduct("libdataproc", :libdataproc),
+                  ExecutableProduct("mungify", :mungify_exe)
+              ]
+              ```
+
+              With such products defined, `Example_jll` would contain `data_txt`, `libdataproc` and `mungify_exe` symbols exported. For `FileProduct` variables, the exported value is a string pointing to the location of the file on-disk.  For `LibraryProduct` variables, it is a string corresponding to the `SONAME` of the desired library (it will have already been `dlopen()`'ed, so typical `ccall()` usage applies), and for `ExecutableProduct` variables, the exported value is a function that can be called to set appropriate environment variables.  Example:
+
+              ```julia
+              using Example_jll
+
+              # For file products, you can access its file location directly:
+              data_lines = open(data_txt, "r") do io
+                  readlines(io)
+              end
+
+              # For library products, you can use the exported variable name in `ccall()` invocations directly
+              num_chars = ccall((libdataproc, :count_characters), Cint, (Cstring, Cint), data_lines[1], length(data_lines[1]))
+
+              # For executable products, you can use the exported variable name as a function that you can call
+              mungify_exe() do mungify_exe_path
+                  run(`\$mungify_exe_path \$num_chars`)
+              end
+              ```
+              """)
     end
 
     # Generate LICENSE.md