From 8a2579a440346f682e8e65ff861d87a25df4539b Mon Sep 17 00:00:00 2001 From: Huan Wang Date: Thu, 21 May 2020 00:39:57 -0600 Subject: add jsonnet --- jsonnet.html.markdown | 139 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 139 insertions(+) create mode 100644 jsonnet.html.markdown (limited to 'jsonnet.html.markdown') diff --git a/jsonnet.html.markdown b/jsonnet.html.markdown new file mode 100644 index 00000000..175642d4 --- /dev/null +++ b/jsonnet.html.markdown @@ -0,0 +1,139 @@ +--- +language: jsonnet +filename: learnjsonnet.jsonnet +contributors: + - ["Huan Wang", "https://github.com/fredwangwang"] +--- + +Jsonnet is a powerful templating language for JSON. Any valid JSON +document is a valid Jsonnet object. For an interactive demo/tutorial, +click [here](https://jsonnet.org/learning/tutorial.html) + +```python +// single line comment + +/* + multiline comment +*/ + +// as well as python style comment + +# define a variable. +# Variables have no effect in the generated JSON without being used. +local num1 = 1; +local num2 = 1 + 1; +local num3 = 5 - 2; +local num4 = 9 % 5; +local num5 = 10 / 2.0; +# jsonnet is a lazy language, if a variable is not used, it is not evaluated. +local num_runtime_error = 1 / 0; + +# fields are valid identifiers without quotes +local obj1 = { a: 'letter a', B: 'letter B' }; + +local arr1 = ['a', 'b', 'c']; + +# string literals use " or '. +local str1 = 'a' + 'B'; +# multiline text literal in between ||| +# Each line must start with a white space. +local str_multiline = ||| + this is a + multiline string +|||; +# Python-compatible string formatting is available via % +# When combined with ||| this can be used for templating text files. +local str_templating = ||| + %(f1)0.3f +||| % { f1: 1.2345678 }; +assert str_templating == '1.235\n'; + +# if b then e else e. The else branch is optional and defaults to null +local var1 = if 3 < 2 then "YES"; +assert var1 == null; + +local obj2 = { + # variable defined inside the object ends with ',' + local var_in_obj = 0, + + local vowels = ['a', 'e', 'i', 'o', 'u'], + local numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], + + # [num] to look up an array element + first_vowel: vowels[0], + # can also slice the array like in Python + even_numbers: numbers[1::2], + + # python-style list and object comprehensions are also supported + double_numbers: [x * 2 for x in numbers], + even_numbers_map: { + # [ ] syntax in field name is to compute the field name dynamically + [x + '_is_even']: true for x in numbers if x % 2 == 0 + }, + + nested: { + nested_field1: 'some-value', + # self refers to the current object + # ["field-name"] or .field-name can be used to look up a field + nested_field2: self.nested_field1, + nested_field3: self.nested_field1, + # $ refers to outer-most object + nested_field4: $.first_vowel, + + assert self.nested_field1 == self.nested_field2, + assert self.nested_field1 == self.nested_field3, + }, + + special_field: 'EVERYTHING FEELS BAD', +}; + +local obj3 = { + local var_in_obj = 1.234, + local var_in_obj2 = { a: { b: 'c' } }, + + concat_array: [1, 2, 3] + [4], + # strings can be concat with +, + # which implicitly converts one operand to string if needed. + concat_string: '123' + 4, + + # == tests deep equality + equals: { a: { b: 'c', d: {} } } == var_in_obj2, + + special_field: 'this feels good', +}; + +# objects can be merged with + where the right-hand side wins field conflicts +local obj4 = obj2 + obj3; +assert obj4.special_field == 'this feels good'; + +# define a function +# functions have positional parameters, named parameters, and default arguments +local my_function(x, y, z=1) = x + y - z; +local num6 = my_function(7, 8, 9); +local num7 = my_function(8, z=10, y=9); +local num8 = my_function(4, 5); +# inline anonymous function +local num9 = (function(x) x * x)(3); + +local obj5 = { + # define a method + # fields defined with :: are hidden, which does not apper in generated JSON + # function cannot be serialized so need to be hidden + # if the object is used in the generated JSON. + is_odd(x):: x % 2 == 1, +}; +assert obj5 == {}; + +# a jsonnet doucment have to evaluate to something +# be it an object, list, number or just string literal +"FIN" + +``` + +## Further Reading +There are a few but important concepts that are not touched in this exmaple, including: + +- Passing variables from command line: [Parameterize Entire Config](https://jsonnet.org/learning/tutorial.html#parameterize-entire-config) +- Import other jsonnet libraries/files: [Imports](https://jsonnet.org/learning/tutorial.html#imports) +- In depth example of OOP aspect of Jsonnet: [Object-Orientation](https://jsonnet.org/learning/tutorial.html#Object-Orientation) +- Useful standard library: [Stdlib](https://jsonnet.org/ref/stdlib.html) -- cgit v1.2.3 From 4ecbc8e69b91195752490d5e00677ad64b9596ae Mon Sep 17 00:00:00 2001 From: Ruofeng Lei Date: Fri, 10 Jul 2020 16:20:30 +0800 Subject: Update jsonnet.html.markdown --- jsonnet.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'jsonnet.html.markdown') diff --git a/jsonnet.html.markdown b/jsonnet.html.markdown index 175642d4..9fe4edbe 100644 --- a/jsonnet.html.markdown +++ b/jsonnet.html.markdown @@ -16,7 +16,7 @@ click [here](https://jsonnet.org/learning/tutorial.html) multiline comment */ -// as well as python style comment +# as well as python style comment # define a variable. # Variables have no effect in the generated JSON without being used. -- cgit v1.2.3