[llvm-branch-commits] [llvm] [Dexter] Document the structured script model (PR #204365)

[Orlando Cazalet-Hyams via llvm-branch-commits]

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+# Dexter Script Testing
+
+Dexter's script mode can be accessed by using the `--use-script` flag.
+
+Dexter scripts are represented by YAML documents, which contain various "nodes" instructing Dexter how to step through the debuggee program, what information to collect and store from the debugger, and how to evaluate the result. A simple Dexter script looks something like this:
+
+```yaml
+---
+!where {function: foo}:
+    !value arg: 5
+    !type arg: int
+    !and {lines: !range [10, 14]}:
+        !value local: ['a', 'b', 'c']
+!where {function: bar}:
+    !where {function: baz}:
+        !step exactly: [20, 21, 22, 23, 24]
+...
+```
+
+This Dexter test checks that:
+- When the debugger steps into `foo`, the type and value of `arg` is always `(int) 5`.
+- While the debugger is in `foo` and the current line is between 10 and 14 (inclusive), the value of `local` is `'a'`, `'b'`, or `'c'`.
+- While the debugger is in the function `baz`, which was called directly from the function `bar`, the lines that the debugger steps through exactly the lines 20-24 in order.
+
+The Dexter test follows a structure based on the nodes - in the example above, each line starts with a node. Some of the basic types of node are:
+
+- `!where` describes a single stack frame using either a function name or a filename + line range; these will be used by the debugger to set breakpoints. We consider a `!where` node to be "active" when the current stack frame matches the `!where` node. A `!where` node can either appear at the "root" of the script, or it can appear as the child of another `!where`, in which case it will only be active when its parent `!where` matches the frame above it. For example, the `!where {function: baz}` node is only active when the next frame up is `bar`, matching its parent.
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OCHyams wrote:

I know it seems obvious, but is it possibly worth spelling out that indentation is required to make a node a child of another?

https://github.com/llvm/llvm-project/pull/204365