New syntax for customize mode (#1709)

* Customize mode new assignment syntax, part 1

* Add StaticPathField parsing rule

* Add cli assignment parsing rule

* Use new assignment parsing rule, refactor common code

* Fix compilation warnings

* Improve the output of `-- list` including type and contracts

* Remove unused datatype

* Formatting

* Fix old tests and add new for customize mode

* Reword documentation of FieldInterface::is_input

* Pass on code documentation

* Remove obsolete comment

* Update cli/tests/snapshot/inputs/customize-mode/unknown_override.ncl

Co-authored-by: jneem <joeneeman@gmail.com>

* Update cli/tests/snapshot/inputs/customize-mode/unkonwn_field_path.ncl

Co-authored-by: jneem <joeneeman@gmail.com>

* Update cli/src/customize/interface.rs

Co-authored-by: jneem <joeneeman@gmail.com>

* Fix typos in snapshot tests

* Add suggestion for customize mode unknown field errors

* Update snapshot tests with new output

* Get rid of '-- show', hint at using query instead

---------

Co-authored-by: jneem <joeneeman@gmail.com>

cli/src/customize/interface.rs

@@ -0,0 +1,218 @@
+//! This module defines the interface of a Nickel configuration which is used to derive the
+//! customize mode of the command-line.
+use super::*;
+
+/// The interface of a configuration (a Nickel program) which represents all nested field paths
+/// that are accessible from the root term together with their associated metadata.
+///
+/// Interface is used to derive a command-line interface from a configuration when using the
+/// `customize_mode` option.
+#[derive(Debug, Clone, Default)]
+pub(super) struct TermInterface {
+    pub(super) fields: HashMap<LocIdent, FieldInterface>,
+}
+
+/// The interface of a specific field. This field can be itself a record and contain subfields.
+#[derive(Debug, Clone, Default)]
+pub(super) struct FieldInterface {
+    /// The interface of the subfields of this field, if it's a record itself.
+    pub(super) subfields: Option<TermInterface>,
+    pub(super) field: Field,
+}
+
+impl Combine for TermInterface {
+    fn combine(first: Self, second: Self) -> Self {
+        let TermInterface { mut fields } = first;
+
+        for (id, field) in second.fields.into_iter() {
+            if let Some(prev) = fields.remove(&id) {
+                fields.insert(id, Combine::combine(prev, field));
+            } else {
+                fields.insert(id, field);
+            }
+        }
+
+        TermInterface { fields }
+    }
+}
+
+impl Combine for FieldInterface {
+    fn combine(first: Self, second: Self) -> Self {
+        FieldInterface {
+            subfields: Combine::combine(first.subfields, second.subfields),
+            field: Field {
+                metadata: Combine::combine(first.field.metadata, second.field.metadata),
+                // Value is used only to show a default value, and to determine if a field has a
+                // definition. We don't bother actually merging the content, but just keep any
+                // side that is defined.
+                value: first.field.value.or(second.field.value),
+                ..Default::default()
+            },
+        }
+    }
+}
+
+impl From<&RecordData> for TermInterface {
+    fn from(value: &RecordData) -> Self {
+        TermInterface {
+            fields: value
+                .fields
+                .iter()
+                .map(|(id, field)| (*id, field.into()))
+                .collect(),
+        }
+    }
+}
+
+impl From<&Term> for TermInterface {
+    fn from(term: &Term) -> Self {
+        term.extract_interface().unwrap_or_default()
+    }
+}
+
+trait ExtractInterface {
+    fn extract_interface(&self) -> Option<TermInterface>;
+}
+
+impl ExtractInterface for &Term {
+    fn extract_interface(&self) -> Option<TermInterface> {
+        if let Term::Record(rd) = self {
+            Some(TermInterface::from(rd))
+        } else {
+            None
+        }
+    }
+}
+
+impl ExtractInterface for Field {
+    fn extract_interface(&self) -> Option<TermInterface> {
+        self.value.as_ref().map(|t| TermInterface::from(t.as_ref()))
+    }
+}
+
+impl ExtractInterface for Type {
+    fn extract_interface(&self) -> Option<TermInterface> {
+        match &self.typ {
+            TypeF::Record(rrows) => Some(TermInterface {
+                fields: rrows
+                    .iter()
+                    .filter_map(|item| {
+                        if let RecordRowsIteratorItem::Row(rrow) = item {
+                            Some((rrow.id, FieldInterface::from(&rrow)))
+                        } else {
+                            None
+                        }
+                    })
+                    .collect(),
+            }),
+            // Contract information is already extracted from runtime contracts, which are
+            // evaluated. Here, we focus on pure static type annotations and ignore flat types as
+            // well
+            _ => None,
+        }
+    }
+}
+
+impl ExtractInterface for RuntimeContract {
+    fn extract_interface(&self) -> Option<TermInterface> {
+        self.contract.as_ref().extract_interface()
+    }
+}
+
+impl ExtractInterface for LabeledType {
+    fn extract_interface(&self) -> Option<TermInterface> {
+        self.typ.extract_interface()
+    }
+}
+
+impl From<&Field> for FieldInterface {
+    fn from(field: &Field) -> Self {
+        // We collect field information from all the sources we can: static types and contracts
+        // (both either as type annotations or contract annotations), and the value of the field if
+        // it's a record.
+
+        let subfields_from_types = field
+            .pending_contracts
+            .iter()
+            .map(ExtractInterface::extract_interface);
+
+        let subfields_from_contracts = field
+            .metadata
+            .annotation
+            .iter()
+            .map(ExtractInterface::extract_interface);
+
+        let subfields_from_value = std::iter::once(field.extract_interface());
+
+        let subfields = subfields_from_types
+            .chain(subfields_from_contracts)
+            .chain(subfields_from_value)
+            .reduce(Combine::combine)
+            .flatten();
+
+        FieldInterface {
+            subfields,
+            field: field.clone(),
+        }
+    }
+}
+
+impl From<&RecordRowF<&Type>> for FieldInterface {
+    fn from(rrow: &RecordRowF<&Type>) -> Self {
+        FieldInterface {
+            subfields: rrow.typ.extract_interface(),
+            ..Default::default()
+        }
+    }
+}
+
+impl FieldInterface {
+    /// Define if a field is an input of a configuration that is intended to be filled. If the
+    /// field is not an input, it can only be overridden via `--override`.
+    ///
+    /// Currently, the difference is mostly conceptual: in practice, we simply gather the arguments
+    /// and their values, either via direct positional arguments or `--override` (although the
+    /// latter sets a different priority), and then merge the elaborated record with original term.
+    ///
+    /// However, from a user experience point of view, we want to make a clear distinction between
+    /// filling a bespoke input of a configuration and overriding an existing value. The latter is
+    /// more "low-level" and should only be done knowingly.
+    ///
+    /// Currently, the logic is simply that a field is an input if it doesn't have a definition or
+    /// it has a default priority. This definition might evolve, as there are ongoing discussions
+    /// on what is the meaning of "input", "output", and if those concept should be made
+    /// first-class ([related issue](https://github.com/tweag/nickel/issues/1505)). For now, this
+    /// logic seems to be a reasonable first approximation.
+    pub(super) fn is_input(&self) -> bool {
+        !self.is_defined() || self.is_default()
+    }
+
+    /// Return `true` is the field has a value.
+    pub(super) fn is_defined(&self) -> bool {
+        self.field.value.is_some()
+    }
+
+    /// Return true is the field's merge priority is `default`.
+    pub(super) fn is_default(&self) -> bool {
+        matches!(self.field.metadata.priority, MergePriority::Bottom)
+    }
+
+    pub(super) fn has_subfields(&self) -> bool {
+        matches!(&self.subfields, Some(ref intf) if !intf.fields.is_empty())
+    }
+
+    /// Return the list of the type and contract annotations joined as a comma-separated string, if
+    /// any.
+    pub(super) fn type_and_contracts(&self) -> Option<String> {
+        let annotation = &self.field.metadata.annotation;
+
+        (!annotation.is_empty()).then(|| {
+            let anns: Vec<String> = annotation
+                .iter()
+                .map(|ctr| ctr.label.typ.to_string())
+                .collect();
+
+            anns.join(",")
+        })
+    }
+}