Add JSON snake_case naming policy #54128
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,118 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
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| namespace System.Text.Json | ||
| { | ||
| internal sealed class JsonSnakeCaseNamingPolicy : JsonNamingPolicy | ||
| { | ||
| public override string ConvertName(string name) | ||
| { | ||
| if (string.IsNullOrEmpty(name)) | ||
| { | ||
| return name; | ||
| } | ||
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| if (name.Length == 1) | ||
| { | ||
| return name.ToLowerInvariant(); | ||
| } | ||
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| var result = new ValueStringBuilder(2 * name.Length); | ||
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| bool wroteUnderscorePreviously = false; | ||
| for (int x = 0; x < name.Length; x++) | ||
| { | ||
| var current = name[x]; | ||
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| if (x > 0 && x < name.Length - 1 && char.IsLetter(current)) | ||
| { | ||
| // text somewhere in the middle of the string | ||
| var previous = name[x - 1]; | ||
| var next = name[x + 1]; | ||
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| if (char.IsLetter(previous) && char.IsLetter(next)) | ||
| { | ||
| // in the middle of a bit of text | ||
| var previousUpper = char.IsUpper(previous); | ||
| var currentUpper = char.IsUpper(current); | ||
| var nextUpper = char.IsUpper(next); | ||
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| switch ((previousUpper, currentUpper, nextUpper)) | ||
| { | ||
| case (false, false, false): // aaa | ||
| case ( true, true, true): // AAA | ||
| case ( true, false, false): // Aaa | ||
| { | ||
| // same word | ||
| result.Append(char.ToLowerInvariant(current)); | ||
| wroteUnderscorePreviously = false; | ||
| break; | ||
| } | ||
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| case (false, false, true): // aaA | ||
| case ( true, false, true): // AaA | ||
| { | ||
| // end of word | ||
| result.Append(char.ToLowerInvariant(current)); | ||
| result.Append('_'); | ||
| wroteUnderscorePreviously = true; | ||
| break; | ||
| } | ||
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| case (false, true, true): // aAA | ||
| case ( true, true, false): // AAa | ||
| case (false, true, false): // aAa | ||
| { | ||
| // beginning of word | ||
| if (!wroteUnderscorePreviously) | ||
| { | ||
| result.Append('_'); | ||
| } | ||
| result.Append(char.ToLowerInvariant(current)); | ||
| wroteUnderscorePreviously = false; | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| else | ||
| { | ||
| // beginning or end of text | ||
| result.Append(char.ToLowerInvariant(current)); | ||
| wroteUnderscorePreviously = false; | ||
| } | ||
| } | ||
| else if (char.IsLetter(current)) | ||
| { | ||
| // text at the beginning or the end of the string | ||
| result.Append(char.ToLowerInvariant(current)); | ||
| wroteUnderscorePreviously = false; | ||
| } | ||
| else if (char.IsNumber(current)) | ||
| { | ||
| // a number at any point in the string | ||
| if (x > 0 && !wroteUnderscorePreviously) | ||
| { | ||
| result.Append('_'); | ||
| } | ||
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| result.Append(current); | ||
| wroteUnderscorePreviously = false; | ||
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| if (x < name.Length - 1) | ||
|
There was a problem hiding this comment. Thinking about it more, this condition will likely accidentally trigger if two or more numbers are hit in sequence. In this scenario, what would a user expect the name to be converted to? I know There was a problem hiding this comment. For now I've just left this as |
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| { | ||
| result.Append('_'); | ||
| wroteUnderscorePreviously = true; | ||
| } | ||
| } | ||
| else if (!wroteUnderscorePreviously) | ||
| { | ||
| // any punctuation at any point in the string | ||
| result.Append('_'); | ||
| wroteUnderscorePreviously = true; | ||
| } | ||
| } | ||
|
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| return result.ToString(); | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,52 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
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| using Xunit; | ||
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| namespace System.Text.Json.Serialization.Tests | ||
| { | ||
| public static class SnakeCaseUnitTests | ||
| { | ||
| [Fact] | ||
| public static void ToSnakeCaseTest() | ||
| { | ||
| // These test cases were copied from Json.NET. | ||
| Assert.Equal("url_value", ConvertToSnakeCase("URLValue")); | ||
| Assert.Equal("url", ConvertToSnakeCase("URL")); | ||
| Assert.Equal("id", ConvertToSnakeCase("ID")); | ||
| Assert.Equal("i", ConvertToSnakeCase("I")); | ||
| Assert.Equal("", ConvertToSnakeCase("")); | ||
| Assert.Null(ConvertToSnakeCase(null)); | ||
| Assert.Equal("person", ConvertToSnakeCase("Person")); | ||
| Assert.Equal("i_phone", ConvertToSnakeCase("iPhone")); | ||
| Assert.Equal("i_phone", ConvertToSnakeCase("IPhone")); | ||
| Assert.Equal("i_phone", ConvertToSnakeCase("I Phone")); | ||
| Assert.Equal("i_phone", ConvertToSnakeCase("I Phone")); | ||
| Assert.Equal("_i_phone", ConvertToSnakeCase(" IPhone")); | ||
| Assert.Equal("_i_phone_", ConvertToSnakeCase(" IPhone ")); | ||
| Assert.Equal("is_cia", ConvertToSnakeCase("IsCIA")); | ||
| Assert.Equal("vm_q", ConvertToSnakeCase("VmQ")); | ||
| Assert.Equal("xml_2_json", ConvertToSnakeCase("Xml2Json")); | ||
| Assert.Equal("xml_2_net_6_0_json", ConvertToSnakeCase("Xml2Net60Json")); | ||
| Assert.Equal("sn_ak_ec_as_e", ConvertToSnakeCase("SnAkEcAsE")); | ||
| Assert.Equal("sn_a_k_ec_as_e", ConvertToSnakeCase("SnA__kEcAsE")); | ||
| Assert.Equal("sn_a_k_ec_as_e", ConvertToSnakeCase("SnA__ kEcAsE")); | ||
| Assert.Equal("already_snake_case_", ConvertToSnakeCase("already_snake_case_ ")); | ||
| Assert.Equal("is_json_property", ConvertToSnakeCase("IsJSONProperty")); | ||
| Assert.Equal("shouting_case", ConvertToSnakeCase("SHOUTING_CASE")); | ||
| Assert.Equal("hi_this_is_text_time_to_test_", ConvertToSnakeCase("Hi!! This is text. Time to test.")); | ||
| Assert.Equal("building", ConvertToSnakeCase("BUILDING")); | ||
| Assert.Equal("building_property", ConvertToSnakeCase("BUILDING Property")); | ||
| Assert.Equal("building_property", ConvertToSnakeCase("Building Property")); | ||
| Assert.Equal("building_property", ConvertToSnakeCase("BUILDING PROPERTY")); | ||
| } | ||
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| // Use a helper method since the method is not public. | ||
| private static string ConvertToSnakeCase(string name) | ||
| { | ||
| JsonNamingPolicy policy = JsonNamingPolicy.SnakeCase; | ||
| string value = policy.ConvertName(name); | ||
| return value; | ||
| } | ||
| } | ||
| } |
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I'm not sure 2 * length is a reasonable heuristic here, but I wasn't sure how much bigger the "average" property name would be, so I felt just doubling was safer.
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ABC would turn into a_b_c so the absolute maximum would be (2 * name.Length) - 1
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ABCshould turn intoabcsince the entire string is all the same case; it should be almost the case asIDThere was a problem hiding this comment.
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so AbCdEf would be ab_cd_ef which gives us name.Length + (int)Math.Ceiling(name.Length/(double)2) - 1
Edit: Actually it is more complicated than that. There are also single char numbers. I would still say that
(2 * name.Length) - 1is the absolute maximum in all cases.