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99 lines
2.8 KiB
Markdown
99 lines
2.8 KiB
Markdown
+++
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title = "UCG Statements"
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weight = 4
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sort_by = "weight"
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in_search_index = true
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+++
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Expression Statements
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-------
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The simplest and least useful is the expression statement. It is any valid expression
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followed by a semicolon.
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```
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1;
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4 / 2;
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"foo";
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"foo" + "bar";
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```
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Despite the fact that these are valid the results are thrown away and can essentially
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be considered a noop. If we ever create a repl for ucg statements they may prove more
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useful.
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Named Value Statements
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--------
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### Let statements
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There are two statements that can introduce a named value for a given ucg file. Let
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statnements and import statements. Any collisions in binding names inside a file are
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treated as compile errors. Bindings are immutable and once bound they can't be
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modified.
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```
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let name = "foo";
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```
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### Import Statement
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The import statement imports the contents of another ucg file into the current file
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with a name. The imported files named values are exposed as a tuple in the referencing
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file. It starts with the `import` keyword and is followed by a quoted path to the ucg
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file, the keyword `as`, and a name for the imported values.
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```
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import "dbconfigs.ucg" as dbconfigs;
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let mysqlconf = dbconfigs.mysql;
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```
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Output Statements
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-----------
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Some statements in ucg exist to generate an output. Either a compiled configuration or the results of test assertions.
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### Assert Statements
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The assert statement defines an expression that must evaluate to either true or false.
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Assert statements are noops except during a validation compile. They give you a way to
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assert certains properties about your data and can be used as a form of unit testing
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for your configurations. It starts with the `assert` keyword followed by a valid block
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of ucg statements delimited by `|` characters. The final statement in the in the block
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must evaluate to a boolean expression.
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```
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assert |
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host == "www.example.com";
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|;
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assert |
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select qa, 443, {
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qa = 80,
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prod = 443,
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} == 443;
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|;
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```
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When _test.ucg files are run in a test run then ucg will output a log of all the assertions to stdout. Giving you a simple test harness for your ucg configs.
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### Out Statements
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The Out statement defines the output for a UCG file. It identifies the output
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converter type and an expression that will be output. The output converter type is
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expected to be one of the registered converters (e.g. json, exec) and the artifact
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file will take the same name as the ucg file with the extension replaced by the
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defined extension for that converter.
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For a file named api_config.ucg with the following contents:
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```
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let myconf = {
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api_url = "https://example.org/api/v1/",
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api_token = env.API_TOKEN,
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};
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out json myconf;
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```
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ucg will output the myconf tuple as json to a file called api_config.json
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Next: <a href="converters">Converters</a> |