Add lambda support for CommandLineNode.commandLine

[Copilot]

CommandLineNode.commandLine only supported string templates formatted with .format(**vars). This adds support for it to also be a callable (lambda/function) taking a node argument, evaluated at build time instead.

Description

Users can now define commandLine as a lambda receiving the node, enabling dynamic command line construction based on node state:

class MyNode(desc.CommandLineNode):
    # New: lambda receiving the node
    commandLine = lambda node: f"myapp --input {node.input.value} --output {node.output.value}"

    # Existing: string template (unchanged)
    # commandLine = "myapp --input {inputValue} --output {outputValue}"

Features list

• CommandLineNode.commandLine accepts a callable (node) -> str in addition to a string template.

Implementation remarks

When a lambda is assigned as a class variable, Python's descriptor protocol wraps it as a bound method on instance access — passing self (the node descriptor) as the first argument, not node. inspect.getattr_static bypasses this, retrieving the raw callable so it can be invoked with just chunk.node.

# meshroom/core/desc/node.py
commandLineValue = getattr_static(self, 'commandLine')
if callable(commandLineValue):
    cmd = commandLineValue(chunk.node)
else:
    cmd = commandLineValue.format(**chunk.node._expVars, **chunk.node._staticExpVars, **cmdLineVars)

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[fabiencastan]

Suggested change

	commandLineValue = getattr_static(self, 'commandLine')
	# In the case of a lambda, we want a single "node" argument and not the node descriptor "self".
	# Therefore, we use getattr_static to retrieve the raw lambda instead of a bound method, which
	# would impose "self" as the first argument if we accessed "self.commandLine".
	commandLineValue = getattr_static(self, 'commandLine')