feat(validation): warn about missing variables used as bare condition operands

[vaceslav]

Changes

ValidateTemplate(template, data) now warns when a condition tests a variable that is missing from the data for truthiness on its own (a bare operand). Such a variable is silently false, which usually hides a typo ({{#if IsActiv}}).

• New ValidationWarningType.MissingConditionVariable = 2. The message names the variable and the condition: Condition 'A and Missing' uses variable 'Missing', which is not provided in the data. It is treated as false. Location is the marker ({{#if A and Missing}}).
• Bare operands are found in the parsed condition AST (ConditionalEvaluator.CollectBareOperandVariables): the whole condition, and the operands of and / or / not. Nested operator nodes are always descended into.
• Reported: {{#if Missing}}, {{#if not Missing}}, {{#if A and Missing}}, {{#elseif Missing}}, inline {{#if Missing}}x{{/if}}, table-row conditionals, headers/footers, and conditions inside loops. Inside loops the check uses the same scoped resolution as missing placeholders: item properties, named iteration variables, globals resolve, and @metadata / . / this are skipped. Conditions in loops over empty collections are not checked, the same as placeholders.
• Not reported: operands of exists / is empty / is not empty (they are meant for missing values); comparison operands (Status = Active bareword fallback stays as it is); in and the string operators; invalid conditions (already an InvalidConditionalExpression error); validation without data.
• Inline {{(...)}} expressions are not checked (decision). Today the validator reports a whole inline expression as one missing variable (Variable '(A and B)' is referenced ... but not provided), even when every operand is present. That is a separate existing false positive. A bare-operand warning on top of it would report the same expression twice. The right fix is to validate inline expressions through the AST instead, which is a behavior change to Errors/IsValid, so it belongs in its own PR.
• The warning is not added to MissingVariables or Errors, and IsValid does not change. Existing DOCX consumers see only an additional warning.
• One shared implementation (Core/MissingConditionVariableCheck.cs), called from ScopedVariableValidator (DOCX) and from the OdtTemplateValidator scope walker (ODT). The TemplateProcessor facade therefore gets it too. Each condition/variable pair is reported once.
• Docs: warning types table in the developer quick start, notes in condition-evaluation and in the conditionals guide for template authors, library README/Examples/ARCHITECTURE.

Tests

• Integration/ValidationMissingConditionVariableTests: every case runs as DOCX and ODT, both directly and through the facade, and asserts identical warnings/errors/missing variables. Covered: bare/not/and/or/grouping/elseif/inline/dotted path; no warning for exists / is empty / is not empty / comparisons / in / string operators / literals; no data; invalid condition; dedupe; several variables; loop scoping (item properties, named vars, @first/@last/@index, this, globals); missing item property in a loop; item property used outside its loop; empty loop; inline expressions; table-row conditional and header.
• Conditionals/CollectBareOperandVariablesTests: the AST walk.
• Odt/OdtValidationParityTests: new "missing bare condition operands" case.
• Release build with -p:ContinuousIntegrationBuild=true (0 warnings), all test projects on net10/9/8, dotnet format --verify-no-changes, dotnet pack, mkdocs build --strict.

Public API impact

Additive: ValidationWarningType.MissingConditionVariable = 2 (in PublicAPI.Unshipped.txt, with XML docs). Behavior change limited to ValidationResult.Warnings: validation with data can return additional warnings. Errors, MissingVariables and IsValid are unchanged.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 96.42857% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...Dev.Templify/Core/MissingConditionVariableCheck.cs	92.85%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!