export v2: Automatically minify output

Automatically format the output JSON file based on file size, unless
either --minify-json or --no-minify-json (new option) is specified.

Functional tests added to cover all code paths. Code to generate a
Newick file was generated by ChatGPT.¹

¹ <https://chat.openai.com/share/5f54c5fe-ee27-4691-bbb4-f71b63970770>

augur/export_v2.py

@@ -1,6 +1,7 @@
 """
 Export version 2 JSON schema for visualization with Auspice
 """
+import os
 from pathlib import Path
 import sys
 import time
@@ -13,9 +14,13 @@
 from .errors import AugurError
 from .io.metadata import DEFAULT_DELIMITERS, DEFAULT_ID_COLUMNS, InvalidDelimiter, read_metadata
 from .types import ValidationMode
-from .utils import read_node_data, write_json, read_config, read_lat_longs, read_colors
+from .utils import read_node_data, write_json, json_size, read_config, read_lat_longs, read_colors
 from .validate import export_v2 as validate_v2, auspice_config_v2 as validate_auspice_config_v2, ValidateError
 
+
+MINIFY_THRESHOLD_MB = 5
+
+
 # Set up warnings & exceptions
 warn = warnings.warn
 deprecationWarningsEmitted = False
@@ -875,10 +880,20 @@ def register_parser(parent_subparsers):
     optional_inputs.add_argument('--colors', metavar="FILE", help="Custom color definitions, one per line in the format `TRAIT_TYPE\\tTRAIT_VALUE\\tHEX_CODE`")
     optional_inputs.add_argument('--lat-longs', metavar="TSV", help="Latitudes and longitudes for geography traits (overrides built in mappings)")
 
+    minify_group = parser.add_argument_group(
+            title="OPTIONAL MINIFY SETTINGS",
+            description=f"""
+                By default, output JSON files (both main and sidecar) are automatically minimized if
+                the size of the un-minified main JSON file exceeds {MINIFY_THRESHOLD_MB} MB. Use
+                these options to override that behavior.
+                """
+        ).add_mutually_exclusive_group()
+    minify_group.add_argument('--minify-json', action="store_true", help="always export JSONs without indentation or line returns.")
+    minify_group.add_argument('--no-minify-json', action="store_true", help="always export JSONs to be human readable.")
+
     optional_settings = parser.add_argument_group(
-        title="OPTIONAL SETTINGS"
+        title="OTHER OPTIONAL SETTINGS"
     )
-    optional_settings.add_argument('--minify-json', action="store_true", help="export JSONs without indentation or line returns")
     root_sequence = optional_settings.add_mutually_exclusive_group()
     root_sequence.add_argument('--include-root-sequence', action="store_true", help="Export an additional JSON containing the root sequence (reference sequence for vcf) used to identify mutations. The filename will follow the pattern of <OUTPUT>_root-sequence.json for a main auspice JSON of <OUTPUT>.json")
     root_sequence.add_argument('--include-root-sequence-inline', action="store_true", help="Export the root sequence (reference sequence for vcf) used to identify mutations as part of the main dataset JSON. This should only be used for small genomes for file size reasons.")
@@ -1165,8 +1180,21 @@ def run(args):
     if config.get("extensions"):
         data_json["meta"]["extensions"] = config["extensions"]
 
+    # Should output be minified?
+    # User-specified arguments take precedence before determining behavior based
+    # on the size of the tree.
+    if args.minify_json or os.environ.get("AUGUR_MINIFY_JSON"):
+        minify = True
+    elif args.no_minify_json:
+        minify = False
+    else:
+        if json_size(data_json) > MINIFY_THRESHOLD_MB * 10**6:
+            minify = True
+        else:
+            minify = False
+
     # Write outputs - the (unified) dataset JSON intended for auspice & perhaps the ref root-sequence JSON
-    indent = {"indent": None} if args.minify_json else {}
+    indent = {"indent": None} if minify else {}
     if args.include_root_sequence or args.include_root_sequence_inline:
         # Note - argparse enforces that only one of these args will be true
         if 'reference' in node_data:

augur/utils.py

@@ -126,6 +126,11 @@ def write_json(data, file_name, indent=(None if os.environ.get("AUGUR_MINIFY_JSO
         json.dump(data, handle, indent=indent, sort_keys=sort_keys, cls=AugurJSONEncoder)
 
 
+def json_size(data, indent=2):
+    """Return size in bytes of a Python object in JSON string form."""
+    return len(json.dumps(data, indent=indent, cls=AugurJSONEncoder))
+
+
 class AugurJSONEncoder(json.JSONEncoder):
     """
     A custom JSONEncoder subclass to serialize data types used for various data

tests/functional/export_v2/cram/minify-output.t

@@ -0,0 +1,90 @@
+Setup
+
+  $ source "$TESTDIR"/_setup.sh
+
+Define a function to generate a Newick tree of a given size. Use lengthy node
+names to create larger file sizes with less recursion.
+
+  $ generate_newick() {
+  >   local n=$1
+  >   local prefix=$(printf 'N%.0s' {1..1000}})
+  >   if [ $n -eq 1 ]; then
+  >        echo "$prefix$n"
+  >    else
+  >        echo "($(generate_newick $((n-1))),$prefix$n)"
+  >    fi
+  > }
+
+A small tree is not automatically minified.
+The unminified output is 16K which is considered acceptable.
+
+  $ echo "$(generate_newick 10);" > small_tree.nwk
+
+  $ ${AUGUR} export v2 \
+  >   --tree small_tree.nwk \
+  >   --skip-validation \
+  >   --output output.json &>/dev/null
+
+  $ head -c 20 output.json
+  {
+    "version": "v2", (no-eol)
+
+  $ du -h output.json
+   16K.* (re)
+
+It can be forcefully minified with an argument.
+
+  $ ${AUGUR} export v2 \
+  >   --tree small_tree.nwk \
+  >   --skip-validation \
+  >   --minify-json \
+  >   --output output.json &>/dev/null
+
+  $ head -c 20 output.json
+  {"version": "v2", "m (no-eol)
+
+It can also be forcefully minified by setting AUGUR_MINIFY_JSON to any value,
+even if it may seem "falsey".
+
+  $ AUGUR_MINIFY_JSON=0 ${AUGUR} export v2 \
+  >   --tree small_tree.nwk \
+  >   --skip-validation \
+  >   --output output.json &>/dev/null
+
+  $ head -c 20 output.json
+  {"version": "v2", "m (no-eol)
+
+  $ du -h output.json
+   12K.* (re)
+
+
+A large tree, when forcefully not minified, has an output size of 7.0M which is
+considered large.
+
+  $ echo "$(generate_newick 500);" > big_tree.nwk
+
+  $ ${AUGUR} export v2 \
+  >   --tree big_tree.nwk \
+  >   --skip-validation \
+  >   --no-minify-json \
+  >   --output output.json &>/dev/null
+
+  $ head -c 20 output.json
+  {
+    "version": "v2", (no-eol)
+
+  $ du -h output.json
+  7.0M.* (re)
+
+This means it is automatically minified.
+
+  $ ${AUGUR} export v2 \
+  >   --tree big_tree.nwk \
+  >   --skip-validation \
+  >   --output output.json &>/dev/null
+
+  $ head -c 20 output.json
+  {"version": "v2", "m (no-eol)
+
+  $ du -h output.json
+  584K.* (re)