Add auto-formatting of json file

Given the just added json-file formatter, we can generate a diff
formatting properly all json files, i.e., all target, rules, and
expression files, by applying that formatter to every target file
and combining the patches. A target description doing precisely
this can easily be obtained as computed root. In this way, we also
make good use of caching. To avoid doing recomputing the target
description unnecessarily, we factor through the tree structure of
the repository tree; the latter, we obtain from the to-git view of
the top-level directory, whereas for computing the diff we use the
actual (not necessarily committed) files.

9 files changed, 324 insertions, 0 deletions

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 6badaf33..bb49ae60 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -28,6 +28,12 @@ is honored. As a consequence, (transitively) depending on the
 first time requires a significant amount of time to build the tools
 from first principles. This is also true when calling `bin/format-code.sh`.
 
+Target, rules, and expression files should be formatted using
+`bin/json-format.py`. The corresponding target is `["@", "format-json", "", ""]`
+which provides a diff to be applied in order to obtain well-formatted
+target, rules, and expression files; the script `bin/format-json.sh`
+computes and applies that diff.
+
 Changes should be organized as a patch series, i.e., as a sequence of
 small changes that are easy to review, but nevertheless self-contained
 in the sense that after each such change, the code builds and the
diff --git a/bin/format-json.sh b/bin/format-json.sh
new file mode 100755
index 00000000..6e1a4439
--- /dev/null
+++ b/bin/format-json.sh
@@ -0,0 +1,19 @@
+#!/bin/sh
+# Copyright 2025 Huawei Cloud Computing Technology Co., Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+: ${JUST_MR:=just-mr}
+
+cd $(readlink -f $(dirname $0)/..)
+${JUST_MR} --main format-json build -p | (patch -p0)
diff --git a/etc/repos.in.json b/etc/repos.in.json
index aab0a492..6b98b384 100644
--- a/etc/repos.in.json
+++ b/etc/repos.in.json
@@ -497,6 +497,32 @@
       , "lzma": "lzma"
       }
     }
+  , "repo":
+    {"repository": {"type": "file", "path": ".", "pragma": {"to_git": true}}}
+  , "format-json infra":
+    { "repository":
+      {"type": "file", "path": "format-json", "pragma": {"to_git": true}}
+    }
+  , "repo tree":
+    { "repository": {"type": "tree structure", "repo": "repo"}
+    , "target_file_name": "TARGETS.tasks"
+    , "target_root": "format-json infra"
+    , "bindings": {"format": "format-json infra"}
+    }
+  , "format-json/tasks":
+    { "repository":
+      {"type": "computed", "repo": "repo tree", "target": ["", ""]}
+    }
+  , "format-json/bin":
+    { "repository": {"type": "file", "path": "bin", "pragma": {"to_git": true}}
+    , "target_root": "format-json infra"
+    }
+  , "format-json":
+    { "repository": {"type": "file", "path": "."}
+    , "target_root": "format-json/tasks"
+    , "rule_root": "format-json infra"
+    , "bindings": {"bin": "format-json/bin"}
+    }
   }
 , "imports":
   [ { "source": "git"
diff --git a/etc/repos.json b/etc/repos.json
index d444c262..fdc5e57f 100644
--- a/etc/repos.json
+++ b/etc/repos.json
@@ -657,6 +657,66 @@
         "lzma": "lzma"
       }
     },
+    "repo": {
+      "repository": {
+        "type": "file",
+        "path": ".",
+        "pragma": {
+          "to_git": true
+        }
+      }
+    },
+    "format-json infra": {
+      "repository": {
+        "type": "file",
+        "path": "format-json",
+        "pragma": {
+          "to_git": true
+        }
+      }
+    },
+    "repo tree": {
+      "repository": {
+        "type": "tree structure",
+        "repo": "repo"
+      },
+      "target_file_name": "TARGETS.tasks",
+      "target_root": "format-json infra",
+      "bindings": {
+        "format": "format-json infra"
+      }
+    },
+    "format-json/tasks": {
+      "repository": {
+        "type": "computed",
+        "repo": "repo tree",
+        "target": [
+          "",
+          ""
+        ]
+      }
+    },
+    "format-json/bin": {
+      "repository": {
+        "type": "file",
+        "path": "bin",
+        "pragma": {
+          "to_git": true
+        }
+      },
+      "target_root": "format-json infra"
+    },
+    "format-json": {
+      "repository": {
+        "type": "file",
+        "path": "."
+      },
+      "target_root": "format-json/tasks",
+      "rule_root": "format-json infra",
+      "bindings": {
+        "bin": "format-json/bin"
+      }
+    },
     "clang-18": {
       "repository": "clang-18/toolchains",
       "target_file_name": "clang.TARGETS",
diff --git a/format-json/EXPRESSIONS b/format-json/EXPRESSIONS
new file mode 100644
index 00000000..f1ca6f4a
--- /dev/null
+++ b/format-json/EXPRESSIONS
@@ -0,0 +1,46 @@
+{ "stage_singleton_field":
+  { "vars": ["fieldname", "transition", "location"]
+  , "expression":
+    { "type": "assert_non_empty"
+    , "msg":
+      ["No artifact specified in field", {"type": "var", "name": "fieldname"}]
+    , "$1":
+      { "type": "disjoint_map_union"
+      , "msg":
+        [ "Expecting (essentially) a single artifact in field"
+        , {"type": "var", "name": "fieldname"}
+        ]
+      , "$1":
+        { "type": "foreach"
+        , "var": "src"
+        , "range":
+          {"type": "FIELD", "name": {"type": "var", "name": "fieldname"}}
+        , "body":
+          { "type": "disjoint_map_union"
+          , "$1":
+            { "type": "foreach"
+            , "var": "artifact"
+            , "range":
+              { "type": "values"
+              , "$1":
+                { "type": "DEP_ARTIFACTS"
+                , "dep": {"type": "var", "name": "src"}
+                , "transition":
+                  { "type": "var"
+                  , "name": "transition"
+                  , "default": {"type": "empty_map"}
+                  }
+                }
+              }
+            , "body":
+              { "type": "singleton_map"
+              , "key": {"type": "var", "name": "location"}
+              , "value": {"type": "var", "name": "artifact"}
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
diff --git a/format-json/RULES b/format-json/RULES
new file mode 100644
index 00000000..1bfb36cb
--- /dev/null
+++ b/format-json/RULES
@@ -0,0 +1,126 @@
+{ "fmt":
+  { "target_fields": ["files"]
+  , "implicit": {"formatter": [["@", "bin", "", "json-format.py"]]}
+  , "imports": {"stage": "stage_singleton_field"}
+  , "tainted": ["lint"]
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ ["fieldname", "formatter"]
+      , ["location", "format"]
+      , ["format", {"type": "CALL_EXPRESSION", "name": "stage"}]
+      , [ "diffs"
+        , { "type": "disjoint_map_union"
+          , "$1":
+            { "type": "foreach"
+            , "var": "dep"
+            , "range": {"type": "FIELD", "name": "files"}
+            , "body":
+              { "type": "disjoint_map_union"
+              , "$1":
+                { "type": "foreach_map"
+                , "range":
+                  { "type": "DEP_ARTIFACTS"
+                  , "dep": {"type": "var", "name": "dep"}
+                  }
+                , "body":
+                  { "type": "ACTION"
+                  , "outs":
+                    [ { "type": "join"
+                      , "$1": [{"type": "var", "name": "_"}, ".diff"]
+                      }
+                    ]
+                  , "inputs":
+                    { "type": "disjoint_map_union"
+                    , "$1":
+                      [ {"type": "var", "name": "format"}
+                      , { "type": "singleton_map"
+                        , "key":
+                          { "type": "join"
+                          , "$1": [{"type": "var", "name": "_"}, ".orig"]
+                          }
+                        , "value": {"type": "var", "name": "$_"}
+                        }
+                      ]
+                    }
+                  , "cmd":
+                    [ "sh"
+                    , "-c"
+                    , { "type": "join"
+                      , "separator": " "
+                      , "$1":
+                        [ "./format -s"
+                        , { "type": "join_cmd"
+                          , "$1":
+                            [ { "type": "join"
+                              , "$1": [{"type": "var", "name": "_"}, ".orig"]
+                              }
+                            ]
+                          }
+                        , ">"
+                        , { "type": "join_cmd"
+                          , "$1": [{"type": "var", "name": "_"}]
+                          }
+                        , "&& diff -u"
+                        , { "type": "join_cmd"
+                          , "$1":
+                            [ { "type": "join"
+                              , "$1": [{"type": "var", "name": "_"}, ".orig"]
+                              }
+                            ]
+                          }
+                        , { "type": "join_cmd"
+                          , "$1": [{"type": "var", "name": "_"}]
+                          }
+                        , ">"
+                        , { "type": "join_cmd"
+                          , "$1":
+                            [ { "type": "join"
+                              , "$1": [{"type": "var", "name": "_"}, ".diff"]
+                              }
+                            ]
+                          }
+                        ]
+                      }
+                    ]
+                  , "may_fail": ["lint"]
+                  , "fail_message":
+                    { "type": "join"
+                    , "$1":
+                      [ "Target file "
+                      , {"type": "var", "name": "_"}
+                      , " not formatted correctly."
+                      ]
+                    }
+                  }
+                }
+              }
+            }
+          }
+        ]
+      , [ "diff"
+        , { "type": "ACTION"
+          , "inputs": {"type": "var", "name": "diffs"}
+          , "outs": ["targets.diff"]
+          , "cmd":
+            [ "sh"
+            , "-c"
+            , { "type": "join"
+              , "separator": " "
+              , "$1":
+                [ "cat"
+                , { "type": "join_cmd"
+                  , "$1":
+                    {"type": "keys", "$1": {"type": "var", "name": "diffs"}}
+                  }
+                , "> targets.diff"
+                ]
+              }
+            ]
+          }
+        ]
+      ]
+    , "body": {"type": "RESULT", "artifacts": {"type": "var", "name": "diff"}}
+    }
+  }
+}
diff --git a/format-json/TARGETS b/format-json/TARGETS
new file mode 100644
index 00000000..0967ef42
--- /dev/null
+++ b/format-json/TARGETS
@@ -0,0 +1 @@
+{}
diff --git a/format-json/TARGETS.tasks b/format-json/TARGETS.tasks
new file mode 100644
index 00000000..2eb54fb8
--- /dev/null
+++ b/format-json/TARGETS.tasks
@@ -0,0 +1,16 @@
+{ "ls":
+  { "type": "generic"
+  , "outs": ["json-files"]
+  , "cmds":
+    [ "find . '(' -name 'TARGETS*' -o -name RULES -o -name EXPRESSIONS ')' -type f > json-files"
+    ]
+  , "deps": [["TREE", null, "."]]
+  }
+, "targets":
+  { "type": "generic"
+  , "outs": ["TARGETS"]
+  , "cmds": ["python3 generate-fmt.py"]
+  , "deps": ["ls", ["@", "format", "", "generate-fmt.py"]]
+  }
+, "": {"type": "export", "target": "targets"}
+}
diff --git a/format-json/generate-fmt.py b/format-json/generate-fmt.py
new file mode 100644
index 00000000..de2c5391
--- /dev/null
+++ b/format-json/generate-fmt.py
@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+# Copyright 2025 Huawei Cloud Computing Technology Co., Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import json
+
+with open("json-files") as f:
+    tfiles = f.read().splitlines()
+
+targets = {"": {"type": "fmt", "files": [t.removeprefix("./") for t in tfiles]}}
+
+with open("TARGETS", "w") as f:
+    json.dump(targets, f, indent=2)