From 185286f97c92233da549a2ff794f73503a1cc26d Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Tue, 30 Aug 2022 19:02:49 +1200
Subject: [PATCH 01/22] add OrderedCollections to test deps

---
 Project.toml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index 81553de..483f7a6 100644
--- a/Project.toml
+++ b/Project.toml
@@ -19,9 +19,10 @@ DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 Distances = "b4f34e82-e78d-54a5-968a-f98e89d6e8f7"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 Markdown = "d6f4376e-aef5-505a-96c1-9c027394607a"
+OrderedCollections = "bac558e1-5e72-5ebc-8fee-abe8a469f55d"
 ScientificTypes = "321657f4-b219-11e9-178b-2701a2544e81"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["CategoricalArrays", "DataFrames", "Distances", "InteractiveUtils", "Markdown", "ScientificTypes", "Tables", "Test"]
+test = ["CategoricalArrays", "DataFrames", "Distances", "InteractiveUtils", "Markdown", "OrderedCollections", "ScientificTypes", "Tables", "Test"]

From 1dbae102861e9401017cd6e1a6dce9e70becd1af Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Tue, 30 Aug 2022 19:11:59 +1200
Subject: [PATCH 02/22] fix a deprecation warning

---
 test/data_utils.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/data_utils.jl b/test/data_utils.jl
index 012ff25..6c1eb75 100644
--- a/test/data_utils.jl
+++ b/test/data_utils.jl
@@ -323,9 +323,9 @@ end
     eval(:(module UserSide
             import MLJModelInterface: metadata_model, metadata_pkg
             struct A end
-            descr = "something"
+            human_name = "Big Foot"
             # Smoke tests.
-            metadata_model(A; descr=descr)
+            metadata_model(A; human_name)
             metadata_pkg(A)
     end))
 end

From 101ffa3e5a8f57f3acecaa75b5babe2ac4d4e0a7 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Tue, 30 Aug 2022 19:12:54 +1200
Subject: [PATCH 03/22] add report method for merging fit reports with
 operation reports

---
 src/model_api.jl  | 36 ++++++++++++++++++++++++++++++++++++
 test/model_api.jl |  8 +++++++-
 test/runtests.jl  |  1 +
 3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index b041adb..31667ef 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -173,6 +173,8 @@ the feature importances from the model's `fitresult` and `report` as an
 abstract vector of `feature::Symbol => importance::Real` pairs
 (e.g `[:gender =>0.23, :height =>0.7, :weight => 0.1]`).
 
+# New model implementations
+
 The following trait overload is also required:
 `MLJModelInterface.reports_feature_importances(::Type{<:M}) = true`
 
@@ -182,3 +184,37 @@ If for some reason a model is sometimes unable to report feature importances the
 
 """
 function feature_importances end
+
+_named_tuple(named_tuple) = named_tuple
+_named_tuple(::Nothing) = NamedTuple()
+
+"""
+    MLJModelInterface.report(model, report_given_method)
+
+Merge the reports in the dictionary `report_given_method` into a single
+property-accessible object. The possible keys of the dictionary are `:fit` and the
+symbolic names of MLJModelInterface.jl operations, such as `:predict` or
+`:transform`. Each value will be the `report` component returned by a training method
+(`fit` or `update`), in the case of `:fit`, or the corresponding operation.
+
+# New model implementations
+
+Overloading this method is optional, unless some value in the dictionary
+`report_given_method` is possibly neither a named tuple nor `nothing`.
+
+A fallback returns the usual named tuple merge of the dictionary values, ignoring any
+`nothing` values. It is the responsibility of the implementation to ensure individual
+reports will never have clashing keys.
+
+"""
+function report(model, report_given_method)
+
+    # Note that we want to avoid copying values in each individual report named tuple, and
+    # merge the reports in a reproducible order.
+
+    methods = collect(keys(report_given_method)) |> sort!
+    reports = [report_given_method[method] for method in methods]
+
+    return merge(reports...)
+end
+
diff --git a/test/model_api.jl b/test/model_api.jl
index 489584c..5875c9e 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -5,7 +5,6 @@ end
     f0::Int
 end
 
-
 mutable struct APIx1 <: Static end
 
 @testset "selectrows(model, data...)" begin
@@ -95,3 +94,10 @@ mutable struct UnivariateFiniteFitter <: Probabilistic end
     @test yhat == fill(DummyUnivariateFinite(), 3)
 
 end
+
+@testset "fallback for `report()` method" begin
+    report_given_method =
+        OrderedCollections.OrderedDict(:predict=>(y=7,), :fit=>(x=1, z=3))
+    @test MLJModelInterface.report(APIx0(f0=1), report_given_method) ==
+        (x=1, z=3, y=7)
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index 69eefe7..693f2da 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -3,6 +3,7 @@ using ScientificTypesBase, ScientificTypes
 using Tables, Distances, CategoricalArrays, InteractiveUtils
 import DataFrames: DataFrame
 import Markdown
+import OrderedCollections
 
 const M  = MLJModelInterface
 const FI = M.FullInterface

From 912f82c9f1c8382c0558596592b2a0b248a47fac Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Wed, 31 Aug 2022 13:14:08 +1200
Subject: [PATCH 04/22] add forgotten switch for `nothing`

---
 src/model_api.jl  | 3 +--
 test/model_api.jl | 6 +++++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index 31667ef..9c2f3ed 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -213,8 +213,7 @@ function report(model, report_given_method)
     # merge the reports in a reproducible order.
 
     methods = collect(keys(report_given_method)) |> sort!
-    reports = [report_given_method[method] for method in methods]
+    reports = [_named_tuple(report_given_method[method]) for method in methods]
 
     return merge(reports...)
 end
-
diff --git a/test/model_api.jl b/test/model_api.jl
index 5875c9e..4347d87 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -97,7 +97,11 @@ end
 
 @testset "fallback for `report()` method" begin
     report_given_method =
-        OrderedCollections.OrderedDict(:predict=>(y=7,), :fit=>(x=1, z=3))
+        OrderedCollections.OrderedDict(
+            :predict=>(y=7,),
+            :fit=>(x=1, z=3),
+            :transform=>nothing,
+        )
     @test MLJModelInterface.report(APIx0(f0=1), report_given_method) ==
         (x=1, z=3, y=7)
 end

From e78f6edff1a33c98d1314bb161f602df47b41fef Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Thu, 1 Sep 2022 11:27:45 +1200
Subject: [PATCH 05/22] tweak warning for bad docstrings

---
 src/metadata_utils.jl | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/metadata_utils.jl b/src/metadata_utils.jl
index 51d6d5a..513d96b 100644
--- a/src/metadata_utils.jl
+++ b/src/metadata_utils.jl
@@ -65,13 +65,16 @@ function _extend!(program::Expr, trait::Symbol, value, T)
     end
 end
 
-const DEPWARN_DOCSTRING =
-    "`metadata_model` should not be called with the keyword argument "*
-    "`descr` or `docstring`. Implementers of the MLJ model interface "*
-    "should instead create an MLJ-compliant docstring in the usual way. "*
-    "See https://alan-turing-institute.github.io/MLJ.jl/dev/adding_models_for_general_use/#Document-strings for details. "
+const depwarn_docstring(T) =
+    """
 
-"""
+    Regarding $T: `metadata_model` should not be called with the keyword argument `descr`
+    or `docstring`. Implementers of the MLJ model interface should instead create an
+    MLJ-compliant docstring in the usual way.  See
+    https://alan-turing-institute.github.io/MLJ.jl/dev/adding_models_for_general_use/#Document-strings
+    for details.
+
+    """
     metadata_model(T; args...)
 
 Helper function to write the metadata for a model `T`.
@@ -122,7 +125,7 @@ function metadata_model(
     supports_training_losses::Union{Nothing,Bool}=nothing,
     reports_feature_importances::Union{Nothing,Bool}=nothing,
 )
-    docstring === nothing || Base.depwarn(DEPWARN_DOCSTRING, :metadata_model)
+    docstring === nothing || Base.depwarn(depwarn_docstring(T), :metadata_model)
 
     program = quote end
 

From cf5c5e3be6cdecc886f71e99b745650617387061 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Thu, 1 Sep 2022 11:34:12 +1200
Subject: [PATCH 06/22] oops

---
 src/metadata_utils.jl | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/metadata_utils.jl b/src/metadata_utils.jl
index 513d96b..d005a67 100644
--- a/src/metadata_utils.jl
+++ b/src/metadata_utils.jl
@@ -75,6 +75,8 @@ const depwarn_docstring(T) =
     for details.
 
     """
+
+"""
     metadata_model(T; args...)
 
 Helper function to write the metadata for a model `T`.

From dc1a12ae24fcf90a1eb727efc34b742e0b130adc Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Tue, 30 Aug 2022 19:02:49 +1200
Subject: [PATCH 07/22] add OrderedCollections to test deps

---
 Project.toml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index 81553de..483f7a6 100644
--- a/Project.toml
+++ b/Project.toml
@@ -19,9 +19,10 @@ DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 Distances = "b4f34e82-e78d-54a5-968a-f98e89d6e8f7"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 Markdown = "d6f4376e-aef5-505a-96c1-9c027394607a"
+OrderedCollections = "bac558e1-5e72-5ebc-8fee-abe8a469f55d"
 ScientificTypes = "321657f4-b219-11e9-178b-2701a2544e81"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["CategoricalArrays", "DataFrames", "Distances", "InteractiveUtils", "Markdown", "ScientificTypes", "Tables", "Test"]
+test = ["CategoricalArrays", "DataFrames", "Distances", "InteractiveUtils", "Markdown", "OrderedCollections", "ScientificTypes", "Tables", "Test"]

From b30f791736795a0363c6fdbcb9000b78f0a2b62b Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Tue, 30 Aug 2022 19:11:59 +1200
Subject: [PATCH 08/22] fix a deprecation warning

---
 test/data_utils.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/data_utils.jl b/test/data_utils.jl
index 012ff25..6c1eb75 100644
--- a/test/data_utils.jl
+++ b/test/data_utils.jl
@@ -323,9 +323,9 @@ end
     eval(:(module UserSide
             import MLJModelInterface: metadata_model, metadata_pkg
             struct A end
-            descr = "something"
+            human_name = "Big Foot"
             # Smoke tests.
-            metadata_model(A; descr=descr)
+            metadata_model(A; human_name)
             metadata_pkg(A)
     end))
 end

From 438a2d2c3fd8c50feab3ab63e2df55295b99db1d Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Tue, 30 Aug 2022 19:12:54 +1200
Subject: [PATCH 09/22] add report method for merging fit reports with
 operation reports

---
 src/model_api.jl  | 36 ++++++++++++++++++++++++++++++++++++
 test/model_api.jl |  8 +++++++-
 test/runtests.jl  |  1 +
 3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index b041adb..31667ef 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -173,6 +173,8 @@ the feature importances from the model's `fitresult` and `report` as an
 abstract vector of `feature::Symbol => importance::Real` pairs
 (e.g `[:gender =>0.23, :height =>0.7, :weight => 0.1]`).
 
+# New model implementations
+
 The following trait overload is also required:
 `MLJModelInterface.reports_feature_importances(::Type{<:M}) = true`
 
@@ -182,3 +184,37 @@ If for some reason a model is sometimes unable to report feature importances the
 
 """
 function feature_importances end
+
+_named_tuple(named_tuple) = named_tuple
+_named_tuple(::Nothing) = NamedTuple()
+
+"""
+    MLJModelInterface.report(model, report_given_method)
+
+Merge the reports in the dictionary `report_given_method` into a single
+property-accessible object. The possible keys of the dictionary are `:fit` and the
+symbolic names of MLJModelInterface.jl operations, such as `:predict` or
+`:transform`. Each value will be the `report` component returned by a training method
+(`fit` or `update`), in the case of `:fit`, or the corresponding operation.
+
+# New model implementations
+
+Overloading this method is optional, unless some value in the dictionary
+`report_given_method` is possibly neither a named tuple nor `nothing`.
+
+A fallback returns the usual named tuple merge of the dictionary values, ignoring any
+`nothing` values. It is the responsibility of the implementation to ensure individual
+reports will never have clashing keys.
+
+"""
+function report(model, report_given_method)
+
+    # Note that we want to avoid copying values in each individual report named tuple, and
+    # merge the reports in a reproducible order.
+
+    methods = collect(keys(report_given_method)) |> sort!
+    reports = [report_given_method[method] for method in methods]
+
+    return merge(reports...)
+end
+
diff --git a/test/model_api.jl b/test/model_api.jl
index 489584c..5875c9e 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -5,7 +5,6 @@ end
     f0::Int
 end
 
-
 mutable struct APIx1 <: Static end
 
 @testset "selectrows(model, data...)" begin
@@ -95,3 +94,10 @@ mutable struct UnivariateFiniteFitter <: Probabilistic end
     @test yhat == fill(DummyUnivariateFinite(), 3)
 
 end
+
+@testset "fallback for `report()` method" begin
+    report_given_method =
+        OrderedCollections.OrderedDict(:predict=>(y=7,), :fit=>(x=1, z=3))
+    @test MLJModelInterface.report(APIx0(f0=1), report_given_method) ==
+        (x=1, z=3, y=7)
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index 69eefe7..693f2da 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -3,6 +3,7 @@ using ScientificTypesBase, ScientificTypes
 using Tables, Distances, CategoricalArrays, InteractiveUtils
 import DataFrames: DataFrame
 import Markdown
+import OrderedCollections
 
 const M  = MLJModelInterface
 const FI = M.FullInterface

From d6983094ad773672cdde17dc7bd87c1b5e63c80b Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Wed, 31 Aug 2022 13:14:08 +1200
Subject: [PATCH 10/22] add forgotten switch for `nothing`

---
 src/model_api.jl  | 3 +--
 test/model_api.jl | 6 +++++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index 31667ef..9c2f3ed 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -213,8 +213,7 @@ function report(model, report_given_method)
     # merge the reports in a reproducible order.
 
     methods = collect(keys(report_given_method)) |> sort!
-    reports = [report_given_method[method] for method in methods]
+    reports = [_named_tuple(report_given_method[method]) for method in methods]
 
     return merge(reports...)
 end
-
diff --git a/test/model_api.jl b/test/model_api.jl
index 5875c9e..4347d87 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -97,7 +97,11 @@ end
 
 @testset "fallback for `report()` method" begin
     report_given_method =
-        OrderedCollections.OrderedDict(:predict=>(y=7,), :fit=>(x=1, z=3))
+        OrderedCollections.OrderedDict(
+            :predict=>(y=7,),
+            :fit=>(x=1, z=3),
+            :transform=>nothing,
+        )
     @test MLJModelInterface.report(APIx0(f0=1), report_given_method) ==
         (x=1, z=3, y=7)
 end

From 3b477ecc645256d4e0c31fde4a21cbb2f8847869 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Wed, 7 Sep 2022 14:24:25 +1200
Subject: [PATCH 11/22] handle clashes in keys of reports

---
 src/model_api.jl  | 24 ++++++++++++++++++------
 test/model_api.jl |  9 +++++++++
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index 9c2f3ed..bfe9a33 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -187,6 +187,8 @@ function feature_importances end
 
 _named_tuple(named_tuple) = named_tuple
 _named_tuple(::Nothing) = NamedTuple()
+_keys(named_tuple) = keys(named_tuple)
+_keys(::Nothing) = ()
 
 """
     MLJModelInterface.report(model, report_given_method)
@@ -195,25 +197,35 @@ Merge the reports in the dictionary `report_given_method` into a single
 property-accessible object. The possible keys of the dictionary are `:fit` and the
 symbolic names of MLJModelInterface.jl operations, such as `:predict` or
 `:transform`. Each value will be the `report` component returned by a training method
-(`fit` or `update`), in the case of `:fit`, or the corresponding operation.
+(`fit` or `update`) dispatched on the `model` type, in the case of `:fit`, or the
+corresponding operation.
 
 # New model implementations
 
-Overloading this method is optional, unless some value in the dictionary
-`report_given_method` is possibly neither a named tuple nor `nothing`.
+Overloading this method is optional, unless `fit`/`update` or an operation generates a
+report that is niether a named tuple nor `nothing`.
 
 A fallback returns the usual named tuple merge of the dictionary values, ignoring any
-`nothing` values. It is the responsibility of the implementation to ensure individual
-reports will never have clashing keys.
+`nothing` values, assuming there are no conflicts between the keys of the dictionary
+values. In that case, each report is first wrapped in a named tuple with one entry, such
+as `(predict=predict_report,)`.
 
 """
 function report(model, report_given_method)
 
+    return_keys = vcat(collect.(_keys.(values(report_given_method)))...)
+    need_to_wrap = return_keys != unique(return_keys)
+
     # Note that we want to avoid copying values in each individual report named tuple, and
     # merge the reports in a reproducible order.
 
     methods = collect(keys(report_given_method)) |> sort!
-    reports = [_named_tuple(report_given_method[method]) for method in methods]
+    reports = map(methods) do method
+        tup = _named_tuple(report_given_method[method])
+        isempty(tup) ? NamedTuple() :
+            need_to_wrap ? NamedTuple{(method,)}((tup,)) :
+            tup
+    end
 
     return merge(reports...)
 end
diff --git a/test/model_api.jl b/test/model_api.jl
index 4347d87..30c6748 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -104,4 +104,13 @@ end
         )
     @test MLJModelInterface.report(APIx0(f0=1), report_given_method) ==
         (x=1, z=3, y=7)
+
+    report_given_method =
+        OrderedCollections.OrderedDict(
+            :predict=>(y=7,),
+            :fit=>(y=1, z=3),
+            :transform=>nothing,
+        )
+    @test MLJModelInterface.report(APIx0(f0=1), report_given_method) ==
+        (fit=(y=1, z=3), predict=(y=7,))
 end

From 06c5971fd147b4b10026224ca4a224b4f79a3e39 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Mon, 12 Sep 2022 09:47:38 +1200
Subject: [PATCH 12/22] improved key clash handling

---
 src/model_api.jl  | 14 +++++++-------
 test/model_api.jl |  2 +-
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index bfe9a33..32d5830 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -194,8 +194,8 @@ _keys(::Nothing) = ()
     MLJModelInterface.report(model, report_given_method)
 
 Merge the reports in the dictionary `report_given_method` into a single
-property-accessible object. The possible keys of the dictionary are `:fit` and the
-symbolic names of MLJModelInterface.jl operations, such as `:predict` or
+property-accessible object. It is supposed that the possible keys of the dictionary are
+`:fit` and the symbolic names of MLJModelInterface.jl operations, such as `:predict` or
 `:transform`. Each value will be the `report` component returned by a training method
 (`fit` or `update`) dispatched on the `model` type, in the case of `:fit`, or the
 corresponding operation.
@@ -203,12 +203,12 @@ corresponding operation.
 # New model implementations
 
 Overloading this method is optional, unless `fit`/`update` or an operation generates a
-report that is niether a named tuple nor `nothing`.
+report that is neither a named tuple nor `nothing`.
 
 A fallback returns the usual named tuple merge of the dictionary values, ignoring any
-`nothing` values, assuming there are no conflicts between the keys of the dictionary
-values. In that case, each report is first wrapped in a named tuple with one entry, such
-as `(predict=predict_report,)`.
+`nothing` values, and assuming there are no conflicts between the keys of the dictionary
+values (the individual reports). If there is a key conflict, all operation reports are
+first wrapped in a named tuple of length one, as in `(predict=predict_report,)`.
 
 """
 function report(model, report_given_method)
@@ -223,7 +223,7 @@ function report(model, report_given_method)
     reports = map(methods) do method
         tup = _named_tuple(report_given_method[method])
         isempty(tup) ? NamedTuple() :
-            need_to_wrap ? NamedTuple{(method,)}((tup,)) :
+            (need_to_wrap && method !== :fit) ? NamedTuple{(method,)}((tup,)) :
             tup
     end
 
diff --git a/test/model_api.jl b/test/model_api.jl
index 30c6748..72f7f92 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -112,5 +112,5 @@ end
             :transform=>nothing,
         )
     @test MLJModelInterface.report(APIx0(f0=1), report_given_method) ==
-        (fit=(y=1, z=3), predict=(y=7,))
+        (y=1, z=3, predict=(y=7,))
 end

From c2aacbab5ab6980fd3de01a7c73127d4fac9a896 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Mon, 12 Sep 2022 11:48:19 +1200
Subject: [PATCH 13/22] empty merged reports should be replaced with `nothing`
 in `report()` fallback

---
 src/model_api.jl  | 4 +++-
 test/model_api.jl | 5 +++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index 32d5830..a9f1572 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -227,5 +227,7 @@ function report(model, report_given_method)
             tup
     end
 
-    return merge(reports...)
+    ret = merge(reports...)
+    isempty(ret) && return nothing
+    return ret
 end
diff --git a/test/model_api.jl b/test/model_api.jl
index 72f7f92..bdb2ca9 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -113,4 +113,9 @@ end
         )
     @test MLJModelInterface.report(APIx0(f0=1), report_given_method) ==
         (y=1, z=3, predict=(y=7,))
+
+    @test MLJModelInterface.report(
+        APIx0(f0=1),
+        OrderedCollections.OrderedDict(:fit => nothing, :transform => NamedTuple()),
+    ) == nothing
 end

From d4a3419041c811c4f98893e82bbe1e28cea71f89 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Thu, 15 Sep 2022 12:01:12 +1200
Subject: [PATCH 14/22] overload fitted_params(::Static, ..) = nothing

---
 src/model_api.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index a9f1572..4f493b8 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -100,7 +100,7 @@ part of the tuple returned by `fit`.
 
 """
 fitted_params(::Model, fitresult) = (fitresult=fitresult,)
-
+fitted_params(::Static, ::Nothing) = nothing
 """
 
     predict(model, fitresult, new_data...)

From 49e128be2436f49ac7b711a4540971b57112a2f1 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Thu, 15 Sep 2022 16:40:39 +1200
Subject: [PATCH 15/22] make merge fallback more robust

---
 src/model_api.jl  | 26 ++++++++++++++++----------
 test/model_api.jl |  7 +++++++
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index 4f493b8..78c7d5b 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -185,8 +185,9 @@ If for some reason a model is sometimes unable to report feature importances the
 """
 function feature_importances end
 
-_named_tuple(named_tuple) = named_tuple
+_named_tuple(named_tuple::NamedTuple) = named_tuple
 _named_tuple(::Nothing) = NamedTuple()
+_named_tuple(something_else) = (report=something_else,)
 _keys(named_tuple) = keys(named_tuple)
 _keys(::Nothing) = ()
 
@@ -194,32 +195,37 @@ _keys(::Nothing) = ()
     MLJModelInterface.report(model, report_given_method)
 
 Merge the reports in the dictionary `report_given_method` into a single
-property-accessible object. It is supposed that the possible keys of the dictionary are
+property-accessible object. It is supposed that the keys of the dictionary are
 `:fit` and the symbolic names of MLJModelInterface.jl operations, such as `:predict` or
 `:transform`. Each value will be the `report` component returned by a training method
 (`fit` or `update`) dispatched on the `model` type, in the case of `:fit`, or the
-corresponding operation.
+report component returned by an operation that supports reporting.
 
 # New model implementations
 
-Overloading this method is optional, unless `fit`/`update` or an operation generates a
-report that is neither a named tuple nor `nothing`.
+Overloading this method is optional, unless the model generates reports that are neither
+named tuples nor `nothing`.
 
-A fallback returns the usual named tuple merge of the dictionary values, ignoring any
-`nothing` values, and assuming there are no conflicts between the keys of the dictionary
-values (the individual reports). If there is a key conflict, all operation reports are
-first wrapped in a named tuple of length one, as in `(predict=predict_report,)`.
+Assuming each dictionary value is a named tuple or `nothing`, the fallback returns the
+usual named tuple merge of the dictionary values, ignoring any `nothing` values, and
+assuming there are no conflicts between the keys of the dictionary values (the individual
+reports). If there is a key conflict, all operation reports are first wrapped in a named
+tuple of length one, as in `(predict=predict_report,)`.
+
+If any dictionary `value` is neither a named tuple nor `nothing`, it is first wrapped as
+`(report=value, )`
 
 """
 function report(model, report_given_method)
 
     return_keys = vcat(collect.(_keys.(values(report_given_method)))...)
-    need_to_wrap = return_keys != unique(return_keys)
 
     # Note that we want to avoid copying values in each individual report named tuple, and
     # merge the reports in a reproducible order.
 
     methods = collect(keys(report_given_method)) |> sort!
+    length(methods) == 1 && return report_given_method[only(methods)]
+    need_to_wrap = return_keys != unique(return_keys)
     reports = map(methods) do method
         tup = _named_tuple(report_given_method[method])
         isempty(tup) ? NamedTuple() :
diff --git a/test/model_api.jl b/test/model_api.jl
index bdb2ca9..dd6664a 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -118,4 +118,11 @@ end
         APIx0(f0=1),
         OrderedCollections.OrderedDict(:fit => nothing, :transform => NamedTuple()),
     ) == nothing
+
+    @test MLJModelInterface.report(
+        APIx0(f0=1),
+        OrderedCollections.OrderedDict(:fit => 42),
+    ) == 42
+
+
 end

From 25986d230b614e3d99539e113d7f9ecf0a48fd70 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Fri, 16 Sep 2022 08:14:53 +1200
Subject: [PATCH 16/22] make sure empty tuples are scrubbed to `nothing` in
 report return value

---
 src/model_api.jl  | 13 ++++++-------
 test/model_api.jl | 12 +++++++++++-
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index 78c7d5b..326b725 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -188,6 +188,8 @@ function feature_importances end
 _named_tuple(named_tuple::NamedTuple) = named_tuple
 _named_tuple(::Nothing) = NamedTuple()
 _named_tuple(something_else) = (report=something_else,)
+_scrub(x) = x
+_scrub(x::NamedTuple) = isempty(x) ? nothing : x
 _keys(named_tuple) = keys(named_tuple)
 _keys(::Nothing) = ()
 
@@ -213,7 +215,7 @@ reports). If there is a key conflict, all operation reports are first wrapped in
 tuple of length one, as in `(predict=predict_report,)`.
 
 If any dictionary `value` is neither a named tuple nor `nothing`, it is first wrapped as
-`(report=value, )`
+`(report=value, )` before merging.
 
 """
 function report(model, report_given_method)
@@ -224,16 +226,13 @@ function report(model, report_given_method)
     # merge the reports in a reproducible order.
 
     methods = collect(keys(report_given_method)) |> sort!
-    length(methods) == 1 && return report_given_method[only(methods)]
+    length(methods) == 1 && return _scrub(report_given_method[only(methods)])
     need_to_wrap = return_keys != unique(return_keys)
     reports = map(methods) do method
         tup = _named_tuple(report_given_method[method])
         isempty(tup) ? NamedTuple() :
             (need_to_wrap && method !== :fit) ? NamedTuple{(method,)}((tup,)) :
-            tup
+                tup
     end
-
-    ret = merge(reports...)
-    isempty(ret) && return nothing
-    return ret
+    return _scrub(merge(reports...))
 end
diff --git a/test/model_api.jl b/test/model_api.jl
index dd6664a..9bacc63 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -117,12 +117,22 @@ end
     @test MLJModelInterface.report(
         APIx0(f0=1),
         OrderedCollections.OrderedDict(:fit => nothing, :transform => NamedTuple()),
-    ) == nothing
+    ) |> isnothing
 
     @test MLJModelInterface.report(
         APIx0(f0=1),
         OrderedCollections.OrderedDict(:fit => 42),
     ) == 42
 
+    @test MLJModelInterface.report(
+        APIx0(f0=1),
+        OrderedCollections.OrderedDict(:fit => nothing),
+    ) |> isnothing
+
+    @test MLJModelInterface.report(
+        APIx0(f0=1),
+        OrderedCollections.OrderedDict(:fit => NamedTuple()),
+    ) |> isnothing
+
 
 end

From 65082874a74230136a1775edad34b6ccb662052f Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Fri, 16 Sep 2022 16:03:22 +1200
Subject: [PATCH 17/22] bump compat julia = "1.6" and update ci

---
 .github/workflows/ci.yml | 1 -
 Project.toml             | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 24170b9..9b5d87f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,7 +17,6 @@ jobs:
       fail-fast: false
       matrix:
         version:
-          - '1.0'
           - '1.6'
           - '1'
         os:
diff --git a/Project.toml b/Project.toml
index 483f7a6..8a1f80c 100644
--- a/Project.toml
+++ b/Project.toml
@@ -11,7 +11,7 @@ StatisticalTraits = "64bff920-2084-43da-a3e6-9bb72801c0c9"
 [compat]
 ScientificTypesBase = "3.0"
 StatisticalTraits = "3.2"
-julia = "1"
+julia = "1.6"
 
 [extras]
 CategoricalArrays = "324d7699-5711-5eae-9e2f-1d82baa6b597"

From ed0fd8c6d365a8cdb21d82ca16ad0bbaa8bb22de Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Fri, 16 Sep 2022 16:20:52 +1200
Subject: [PATCH 18/22] trivial commit

---
 test/model_api.jl | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/test/model_api.jl b/test/model_api.jl
index 9bacc63..452a031 100644
--- a/test/model_api.jl
+++ b/test/model_api.jl
@@ -136,3 +136,5 @@ end
 
 
 end
+
+

From b8ad6f703073c0ec1da762251a1ca1f9936e9df2 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Fri, 23 Sep 2022 10:33:42 +1200
Subject: [PATCH 19/22] rm redundant `const`

---
 src/metadata_utils.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/metadata_utils.jl b/src/metadata_utils.jl
index d005a67..9fda47a 100644
--- a/src/metadata_utils.jl
+++ b/src/metadata_utils.jl
@@ -65,7 +65,7 @@ function _extend!(program::Expr, trait::Symbol, value, T)
     end
 end
 
-const depwarn_docstring(T) =
+depwarn_docstring(T) =
     """
 
     Regarding $T: `metadata_model` should not be called with the keyword argument `descr`

From 82aa20a81f152598be5511cfe58cfbb865f06ef6 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Fri, 23 Sep 2022 10:44:46 +1200
Subject: [PATCH 20/22] improve docstring

oops
---
 src/model_api.jl | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index 326b725..21e55e5 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -197,11 +197,11 @@ _keys(::Nothing) = ()
     MLJModelInterface.report(model, report_given_method)
 
 Merge the reports in the dictionary `report_given_method` into a single
-property-accessible object. It is supposed that the keys of the dictionary are
-`:fit` and the symbolic names of MLJModelInterface.jl operations, such as `:predict` or
-`:transform`. Each value will be the `report` component returned by a training method
-(`fit` or `update`) dispatched on the `model` type, in the case of `:fit`, or the
-report component returned by an operation that supports reporting.
+property-accessible object. It is supposed that each key of the dictionary is either
+`:fit` or the name of an operation, such as `:predict` or `:transform`. Each value will be
+the `report` component returned by a training method (`fit` or `update`) dispatched on the
+`model` type, in the case of `:fit`, or the report component returned by an operation that
+supports reporting.
 
 # New model implementations
 
@@ -212,7 +212,7 @@ Assuming each dictionary value is a named tuple or `nothing`, the fallback retur
 usual named tuple merge of the dictionary values, ignoring any `nothing` values, and
 assuming there are no conflicts between the keys of the dictionary values (the individual
 reports). If there is a key conflict, all operation reports are first wrapped in a named
-tuple of length one, as in `(predict=predict_report,)`.
+tuple of length one, as in `(predict=predict_report,)`. A `:fit` report is never wrapped.
 
 If any dictionary `value` is neither a named tuple nor `nothing`, it is first wrapped as
 `(report=value, )` before merging.

From 2319e858c24bdb52f674a0fb269f69ab9063c723 Mon Sep 17 00:00:00 2001
From: "Anthony Blaom, PhD" <anthony.blaom@gmail.com>
Date: Fri, 23 Sep 2022 10:48:45 +1200
Subject: [PATCH 21/22] tweak docstring

Co-authored-by: Okon Samuel <39421418+OkonSamuel@users.noreply.github.com>
---
 src/model_api.jl | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/model_api.jl b/src/model_api.jl
index 21e55e5..595d905 100644
--- a/src/model_api.jl
+++ b/src/model_api.jl
@@ -208,10 +208,11 @@ supports reporting.
 Overloading this method is optional, unless the model generates reports that are neither
 named tuples nor `nothing`.
 
-Assuming each dictionary value is a named tuple or `nothing`, the fallback returns the
-usual named tuple merge of the dictionary values, ignoring any `nothing` values, and
-assuming there are no conflicts between the keys of the dictionary values (the individual
-reports). If there is a key conflict, all operation reports are first wrapped in a named
+Assuming each value in the `report_given_method` dictionary is either a named tuple 
+or `nothing`, and there are no conflicts between the keys of the dictionary values 
+(the individual reports), the fallback returns the usual named tuple merge of the 
+dictionary values, ignoring any `nothing` value. If there is a key conflict, all operation 
+reports are first wrapped in a named
 tuple of length one, as in `(predict=predict_report,)`. A `:fit` report is never wrapped.
 
 If any dictionary `value` is neither a named tuple nor `nothing`, it is first wrapped as

From a346af91f69760831ce7bd65155e5d2bf51b88e1 Mon Sep 17 00:00:00 2001
From: "Anthony D. Blaom" <anthony.blaom@gmail.com>
Date: Wed, 5 Oct 2022 12:11:05 +1300
Subject: [PATCH 22/22] bump 1.7.0

---
 Project.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index 8a1f80c..02ec4a9 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "MLJModelInterface"
 uuid = "e80e1ace-859a-464e-9ed9-23947d8ae3ea"
 authors = ["Thibaut Lienart and Anthony Blaom"]
-version = "1.6.0"
+version = "1.7.0"
 
 [deps]
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"